Use a New IEEE Commonplace to Design a Safer Digital World For Youngsters



This text was first revealed as “Design case historical past: the Commodore 64.” It appeared within the March 1985 subject of IEEE Spectrum. A PDF model is out there on IEEE Xplore. The diagrams and images of chips, circuit boards, and screens appeared within the unique print model.

Charles Winterble, then director of worldwide engineering for Commodore, gave the go-ahead for the chip effort, and Charpentier’s group labored pretty independently till each chips have been completed in mid-November 1981.

At a gathering with Charpentier and Winterble late that month, Jack Tramiel, then president of Commodore, determined to not proceed with the online game. As a substitute, he determined, the chips would go right into a 64-kilobyte house pc to be launched on the Client Electronics Present in Las Vegas the second week of January 1982. The pc had but to be designed, however that was simply remedied.

In two days, the engineers laid out on paper the machine’s primary structure. Simply earlier than the brand new 12 months, they accomplished 5 working prototypes. Within the meantime, sufficient operating-system software program was copied and rewritten from the VIC-20 to offer satisfactory demonstrations of what the brand new machine might do. Following its enthusiastic reception on the Client Electronics Present, the Commodore 64 was rushed into manufacturing; quantity shipments started in August 1982 and have continued unabated.

Regardless of complaints about high quality management and the trade’s slowest disk drive, the Commodore 64 has been an unparalleled success, pushing a lot of its rivals out of the market. A part of the explanation for its success is the worth, which retains falling—from $595 at its introduction to $149 at present, for which the buyer will get graphics and sound equal to or higher than that supplied by machines that price 5 instances as a lot.

Designing the subsequent nice chips

Within the late Seventies, MOS Know-how was a profitable semiconductor firm; its engineers had designed the favored 6502 microprocessor, and it manufactured a number of different solidly promoting merchandise. Commodore, a West Coast firm on the time, took over MOS in 1976—inflicting lots of the MOS engineers to stop when their inventory was purchased at 10 cents on the greenback—however MOS was allowed to function pretty autonomously.

In 1979 and 1980, remembers Charpentier, MOS Know-how developed the 6510 microprocessor—a minor revision of the 6502 with a further input-output port, the 6526 peripheral controller, loads of read-only reminiscence (ROM) chips, and a 4-kilobit random-access reminiscence (RAM) chip. At the moment, MOS was supplying tools to Atari Inc., Normal Electrical Co., Hewlett-Packard Co., and a lot of different shoppers, in addition to to Commodore.

When the choice was made to design the newest in superior graphics and sound chips, step one was apparent: to seek out what the present high-quality chips might do. In assembling his design group, Charpentier recruited Robert Yannes, a younger engineer who had joined MOS in 1979 and had designed the VIC-20 at house, from a spare prototype board. The group spent about two weeks researching comparable chips industrywide.

“We appeared closely into the Mattel Intellivision,” remembers Winterble. “We additionally examined the Texas Devices 99/4A and the Atari 800. We tried to get a really feel for what these corporations might do sooner or later by extrapolating from their present expertise. That made it clear what the graphics capabilities of our machine needed to be.”

The MOS designers freely borrowed concepts that they favored—sprites from the TI machine, collision-detection strategies and character-mapped graphics from the Intellivision, and a bit map from their very own VIC-20. They then packed as lots of these concepts as they may right into a predefined space of silicon.

“Al [Charpentier] was given the liberty, inside a sure die measurement, to place in every little thing he might, working backward inside the measurement we deliberate. When he ran out of registers he stopped,” stated Winterble. “We outlined upfront the silicon measurement that might give a yield we have been keen to dwell with; at the moment, a die measurement that was affordable in 5-micrometer expertise was lower than 200 mils. Then we prioritized the want listing from what have to be in there to what ought to be in there to what we’d like to have, so the choices that have been wanted at varied factors grew to become pretty automated.”

9 months to first-pass silicon 

For 9 months, Charpentier labored with two draftsmen and one computer-aided-design operator on the graphics chip whereas Yannes labored with two different draftsmen and one CAD operator on the sound chip. They lacked fully the delicate design instruments of right this moment’s engineering workstations, however that they had one available design instrument discovered nearly nowhere else within the home-computer trade: a chip-fabrication line on the premises. With this, Winterble defined, a circuit buried deep contained in the chips may very well be lifted out and run as a take a look at chip, permitting thorough debugging with out concern for different elements of the circuitry. David A. Ziembicki, then a manufacturing engineer at Commodore, remembers that typical fabrication instances have been a number of weeks and that in an emergency the captive fabrication facility might flip designs round in as little as 4 days.

The price of creating the Commodore 64: Nobody is aware of.

The price of creating the Commodore 64: Nobody is aware of. “I had no formal price range accountability,” stated Winterble, “apart from Jack [Tramiel] watching me. Jack stated that budgets have been a license to steal.” As a result of MOS Know-how’s fabrication facility was not working at full capability, the tools used for C-64 take a look at chips and a number of passes of silicon would in any other case have been idle. “We have been utilizing individuals who have been there anyway,” stated Ziembicki. “You waste just a little little bit of silicon, however silicon’s fairly low-cost. It’s solely sand.”

Though customized chips are normally thought-about costly, the C-64 chips weren’t. Not solely have been improvement prices absorbed in firm overhead, however there was no markup to pay, as there would have been inf the chips had been constructed by one other firm. And yields have been excessive as a result of the chips have been designed for a mature semiconductor-manufacturing course of.

The sound chip was designed with 7-micrometer expertise, cutting down to six in locations. (In contrast, the customized chip for Atari’s Video Pc System, fabricated 4 years earlier, was constructed with 6-micrometer expertise.) Commodore’s video chip was designed with 5-micrometer options.

As a result of design time quite than silicon was at a premium, the chips have been laid out merely quite than compactly. “We did it in a really modular vogue,” stated Yannes. For instance, he famous, “the usual manner of constructing oscillators is to construct one after which multiplex it till you might have as many as you want. We simply constructed an oscillator module and repeated it, as a result of that was a lot quicker than understanding all of the timing for the multiplexer.”

“What was outstanding,” Winterble added, “was that 9 months later, once we got here out with the primary move, it functioned apart from one unhealthy sprite.”

In November 1981, the chips have been full. The unique intent had been a sport machine, however at this level the personal-computer market was starting to look promising. At a gathering of Charpentier, Winterble, and Tramiel, the choice was made to go for a private pc. The subsequent option to be made, in accordance with Charpentier, was between a 16-kilobyte and a 64-kilobyte machine, for the reason that customized chips have been designed to deal with both choice.

“Jack [Tramiel] made the guess that by the point we have been prepared to supply a product, 64K Rams could be low-cost sufficient for us to make use of,” Charpentier stated.

When the design of the Commodore 64 started, the overriding objectives have been simplicity and low price. The preliminary manufacturing price of the Commodore 64 was focused at $130; it turned out to be $135. The pc would use the identical case because the VIC-20 and the same-sized circuit board, to hurry improvement. “That wasn’t even a call,” stated Charpentier. “It was simply widespread sense. Should you’ve bought a product that’s a winner, why change it?” To modify from the VIC-20 to the Commodore 64, the manufacturing group had solely to make the cartridge slot smaller, change the colour of the case, and design a brand new label.

Moreover, as a substitute of designing for efficiency first and worth second, as many engineers are inclined to do, the small design group at Commodore had price in thoughts from the start. Yannes, for instance, had made economic system his credo when he was an impecunious high-school pupil searching for elements to construct a sound synthesizer. “Anytime I design one thing, I wish to use the minimal variety of elements doable. It’s a private problem. If there’s a spare [logic] gate in a gate package deal, I’ll work to eliminate your complete package deal, as a result of in working with a sure variety of chips, I ought to have the ability to burn up every little thing that’s in them. The Commodore 64 was my try to construct absolutely the minimal system that may very well be constructed out of the video and sound chips put collectively.”

Completely satisfied New 12 months 1982!

Within the consumer-electronics trade, new merchandise are historically launched to distributors, sellers, the press, and the competitors twice a 12 months—throughout the first weekend in January and the primary weekend in June, on the Winter and Summer season Client Electronics Reveals (CESs).

“While you labored for Commodore,” stated Yannes, “you at all times needed to have one thing for the Winter CES.” The C-64 didn’t have a lot competitors on the winter present in 1982. Atari was nonetheless sowing its 400/800 pc. Mattel launched the Aquarius pc, and Spectravideo launched its pc/sport machine, each with restricted reminiscence and capabilities.

Ziembicki recalled, “All we noticed at our sales space have been Atari folks with their mouths dropping open, saying, ‘How will you try this for $595?’”

“We have been successful,” Winterble added.

After the present, Commodore, which had a popularity for generally exhibiting merchandise that by no means reappeared, needed to get the 64 into manufacturing rapidly. Only some design modifications have been made to prepared the machine for manufacturing. “What’s within the 64 functionally is what I needed,’ Yannes stated. “What’s within the sound chip is what I needed, and what’s within the video chip is what Al [Charpentier] needed.”

In truth, stated Ziembicki, “after it lastly bought into manufacturing, we appeared again and requested, why did we hassle altering it after January? It wouldn’t have offered one unit much less, and we’d have saved some huge cash on improvement prices.”

A few of the modifications have been pretty important, however they might have created as many issues as they solved. The most important enchancment was to treatment “a hiccup” within the video chip, stated Winterble.

When Charpentier first designed the video chip, he defined, his objective was optimum efficiency in each black-and-white and shade. Earlier video chips, equivalent to these used within the Atari and the Apple, had a black-and-white frequency of seven.16 MHz—twice the tv color-clock frequency of three.58 MHz—however this might not squeeze sufficient characters on a line, and it additionally induced cross speak between the 2 alerts, inflicting an object to shift barely to the left or proper on the display relying on its shade. After the January 1982 CES, when he noticed that 40 characters wouldn’t fairly match onto a TV display, Charpentier sped up the black-and-white clock price and made the 2 clocks fully asynchronous. However for the reason that shade and black-and-white units of knowledge have been continually altering part relative to one another, “the colour transitions have been improbable, however there was an general swimming impact,” he recalled. The answer was to place a phase-locked loop into the system so the colour and the black-and-white info would have a continuing relationship. This, Charpentier acknowledged, was “a Band-Assist resolution.”

And that’s what it seems like, in accordance with Craig Nelson, director of product improvement for Epyx Pc Software program of Sunnyvale, Calif. “It’s a extremely elegant circuit,” he stated, “apart from the phase-locked loop, which is simply caught in the midst of it.” (Commodore now says it has redesigned the chip to remove the issue.)

Because of the “Band-Assist,” the colour info and the black-and-white info shift part by 180 levels in relation to one another on successive video fields quite than altering part unpredictably. This conforms extra intently to the Nationwide Tv Techniques Committee (NTSC) normal, which requires black-and-white info to have a clock price that’s an odd harmonic of the color-clock price, in order that the 2 mechanically reverse their relationship each different area—one area in part, the subsequent area out of part. (Within the NTSC normal, colours are decided by the part distinction between the colour sign and a shade reference sign transmitted originally of every line.)

On the time the usual was developed, generally obtainable circuitry couldn’t fully separate the black-and-white info from the colour: modifications in shade would result in modifications in brightness and vice versa. It was to common these modifications out over time that the NTSC specified that the relative part reversal of the 2 alerts might happen on successive fields. The result’s extra pleasing shade transitions, however the part shift makes stationary figures seem to jitter. The jitter is especially apparent on skinny vertical traces, like these in alphanumeric characters. However when the Commodore 64 was conceived, it was to be primarily a sport machine, not a pc.

Operating a 5-micrometer-technology chip at an 8-MHz clock price precipitated it to dissipate an excessive amount of energy—almost 1.5 watts. Not solely did the chip run quick, however to forestall the colours from washing out, as that they had within the VIC-20, “we went to 12 volt to drive the heck out of the colour alerts,” recalled Winterble. “We knew we might have a warmth downside.”

At this level Winterble made one other design repair—welding a small steel tab onto the within of the lid of the shielding enclosure across the video chip. When the pc was assembled, the tab pressed towards the highest of the chip package deal, forming a heat-conducting path and turning the shielding right into a warmth sink.

Some modifications which may have improved the machine didn’t get made within the rush to manufacturing. For instance, Yannes stated, the wires for the sound output on the printed-circuit board run alongside the wires for the video sign. Consequently, the sound output picks up an annoying 15,750 -Hz whine. Rerouting the circuit would have taken time, “and we had a board that labored,” he defined. “At that time, when you had one thing that labored, you didn’t change it.” A circuit-board revision since then has rerouted these traces, Commodore stated.

However the designers did actually change some issues that labored—together with one revision that degraded the machine’s efficiency.

However the designers did actually change some issues that labored—together with one revision that degraded the machine’s efficiency. The unique design specified a high-quality radio-frequency modulator to transmit the sign to a tv set, however a less expensive modulator was substituted. “It was $6.25 to $6.50 for a very good one, and we ended up spending about $3,” Charpentier stated.

Winterble has a distinct view of the $3 modulator: “The 50-cent modulator we have been utilizing on the VIC-20 wasn’t ok,” he stated, “so we went to a costlier one.”

Digital design wasn’t the one troublesome space because the Commodore 64 went from prototype improvement into manufacturing—the logistics posed a posh downside. The C-64 was designed in Norristown, Pa., at MOS. The VIC-20 meeting line, which was to start making C-64s, was in Santa Clara, Calif. Because the C-64 went into manufacturing, Commodore was additionally opening a brand new meeting line in West Chester, Pa. There have been extra VIC-20 meeting amenities in Japan, the place the disk drive for the C-64 was to be manufactured. And the C-64 circuit boards have been being made in Hong Kong.

“It was loads of enjoyable,” stated Ziembicki. “The design folks would choose an English screw. The manufacturing finish would choose metric. However they went with what that they had. Commodore manufacturing was excellent at making issues match whether or not they have been meant to or not. Their constitution was ‘Ship ‘em’”

“It takes a really robust individual,” defined Charpentier, “to say ‘I’m not transport these as a result of they’re not so good as they may very well be’—particularly when individuals are clamoring to purchase them.”

​Modifications proceed throughout manufacturing

The beginning of manufacturing of the Commodore 64 within the spring of 1982 didn’t sign an finish to the controversy. “The secret is to have the ability to remedy your issues when you are working,” stated Ziembicki.

One of many first battles, recalled Charpentier, was over the format of the printed-circuit board. Commodore’s meeting plant in america used automated component-insertion tools, however its Japanese facility didn’t, and the 2 meeting strategies required completely different element spacing. Ultimately, the board for the C-64 was laid out for automated insertion, and manufacturing was moved to a brand new plant in Hong Kong that had the automated instruments.

Issues additionally plagued a lot of the elements—switches, for instance. “You choose a swap that’s listed as a client swap,” stated Ziembicki. “You design it in. You name the producer and get an estimate that sounds affordable. Then California [the production division] desires 50,000 every week, however the producer says, ‘We are able to’t make that. It’s a client swap, however we’re not geared for client portions.’ At that time, you’re hung up.”

Since Commodore had simply moved its engineering employees from California to Pennsylvania, communication between the design engineers and the manufacturing amenities was not excellent, Ziembicki defined. “It bought to the purpose the place you couldn’t cease working even when you didn’t get an answer—you’d simply proceed with the elements that you just thought the manufacturing finish might get.”

And out of doors suppliers weren’t at all times dependable. “One supplied an influence provide for engineering approval,” Ziembicki recalled. “It bought accredited, after which the provider modified the design and didn’t inform anyone.”

Charpentier stated that his relations with the manufacturing group have been pretty agreeable. Winterble’s dealings with them weren’t almost as cordial, however he discovered this acceptable. “I personally needed to play the heavy on loads of stuff,” he stated. “Then Al would go in and do some good. That approach eased loads of stress—it was a technique to get issues performed.”

Essentially the most infamous downside was “sparkle,” a defect that precipitated small spots of sunshine to seem on the show display. The issue was solved earlier than Charpentier left the corporate in September 1982, however reviews of the defect continued nicely into the Christmas season, with press reviews citing it for example of Commodore’s poor high quality management. Canny shoppers used it as an excuse to return completely good Commodore 64s whereas they have been below 90-day guarantee. For the reason that worth of the machine had dropped $200 within the two months following its introduction, this ruse enabled homeowners to acquire a refund of the acquisition worth and purchase one other C-64 on the decrease determine.

Sparkle was broadly attributed to bugs within the video chip that was the center of the system, however actually it was brought on by a ROM chip of which 3 million have been in service with no issues in different programs, together with the hit arcade online game Asteroids. Commodore engineers themselves first appeared for the issue within the video chip. It took them three weeks to identify the ROM chip because the supply of the defect, Charpentier stated. “The issue was a random occasion—it didn’t occur on a regular basis. We thought the video chip was for some motive seeing the incorrect information. We didn’t even suspect it may very well be the ROM. Lastly we put the logic analyzer on it and tracked it down.” The ROM, which Charpentier and his group had designed years earlier, had a particular pre-charging circuit to make it run quicker, however the circuit made it delicate to spurious alerts. The video circuitry and the 6510 microprocessor alternated in controlling the system bus, and when management handed kind one to the opposite, voltage spikes have been generally generated.

“It simply occurred that we hit the precise timing,” Charpentier stated. “If the spike had been a number of nanoseconds shorter or longer, it wouldn’t have been an issue. The spike was simply large sufficient that the ROM noticed it as a legitimate handle. It will ignore the subsequent handle request and provides the video chip incorrect information.” For the reason that ROM contained the C-64 character set, the display show could be affected by random slices of characters.

In keeping with Nelson of Epyx, “This confetti interference-looking stuff on the display, glowingly known as sparkle, has a particularly un-nice property: it causes {hardware} collisions—the sprites imagine it actually exists.” For the reason that sparkle was brought on by inappropriate information fed to the video chip, it triggered the circuitry liable for checking whether or not the movable show objects—sprites—have been overlaying background objects on the display. So software program that trusted collision sensing to manage the motion of objects on the display would go berserk when confronted by sparkle.

The bug within the ROM was corrected, though Commodore needed to depend on exterior suppliers for some time because it ramped up its new manufacturing line. Solely the primary few hundred thousand models shipped had the defect. However, Nelson noticed, “it doesn’t matter to programmers that it was mounted. Our software program has to work in each machine on the market.” One of the best resolution for programmers, he defined, is to repeat the contents of the ROM into RAM, which is dependable. However this wastes 2 kilobytes of RAM.

​“A screw-up in my timing”

Along with the problem with the ROM, “I made a logic error,” Charpentier recalled. The error, which was corrected generally after Charpentier left Commodore, precipitated the early C-64s to generate the incorrect variety of clock cycles on every horizontal video line. “It was off by one,” he stated. “As a substitute of 65 clock cycles per line, I had 64.”

Consequently, the 180-degree part shift between the black-and-white and shade info, which might have eradicated color-transition issues, didn’t happen. Relying on their shade and the colour of the background, the sides of some objects on the display would seem barely out of line. This was corrected roughly 5 months into manufacturing.

However main edges are nonetheless an issue with the C-64. The circuitry that shows both sprite info or background info at any level on the display is typically sluggish to reply and overlays the sprite on the background info solely after it has missed a number of pixels.

The C-64 designers weren’t the one ones revising their machine; even some assembly-line employees bought into the act.

The C-64 designers weren’t the one ones revising their machine; even some assembly-line employees bought into the act. Since testing shade high quality mechanically is nearly unimaginable, assembly-line employees have been instructed to show a potentiometer that controls the colour and black-and-white alerts till they noticed shade. As Charpentier recalled, the employees quickly found that in the event that they turned the potentiometer so far as doable, it resulted in saturated shade—nevertheless it additionally worn out the black-and-white sign. A number of thousand computer systems had been shipped earlier than the assembly-line employees’ “revision” was seen; by then, some reviewers have been lambasting the C-64 for its “garish” colours.

​High quality nonetheless missing

Although these modifications have been made within the C-64 since its introductions, designers who write business software program for the machine wish to see a number of extra. One such change could be sufficient high quality management. “They don’t take a look at,” stated Nelson of Epyx. “I’ve opened up brand-new Commodores and located traces minimize. They clearly use an influence screwdriver to assemble the C-64, generally miss the screw, and chop the traces. How, may you marvel, might which have handed ultimate inspection? Nicely, these traces are hooked as much as the disk-drive connectors, which they clearly don’t take a look at.”

In hindsight, Charpentier referred to as one among Commodore’s errors “not coming just a little nearer to high quality.”

One grievance voiced by designers of add-on {hardware} for the C-64 is that its minimalist design ends in undesirable interactions between elements of the {hardware} and software program. For instance, the circuitry used to manage the joystick and the game-paddle port is borrowed as soon as each 1/60 second to scan the keyboard for keys which have been pressed. If the joystick switches are closed, the keyboard-scanning software program will report {that a} key has been pressed. Gadgets that connect to the joystick ports could cause unpredictable responses—an issue that might not happen if separate {hardware} had been used for the 2 capabilities.

One other flaw is the pc’s crude inner software program. The system comes up in Primary when it’s turned on. This can be a leftover from the times of the primary Pet pc produced by Commodore, which had no disk-operating system, since there have been no disk drives available then. “A good disk-operating system wasn’t developed till Pet Primary 4.0,” Charpentier stated. The C-64 doesn’t use this superior model of Primary as a result of “it will have required extra ROM than we might put in.” As a substitute, the machine makes use of a much more primitive model of Primary, borrowed from the VIC-20.

“Software program wasn’t tangible—you couldn’t maintain it, really feel it, or contact it—so it wasn’t price spending cash for.”

Essentially the most obtrusive omissions from the Commodore 64’s Primary are instructions to manage the sound and graphics chips. “There was by no means any intention that the system would have built-in software program to manage the graphics or the sound,” stated Yannes. “That was an apparent a part of the Commodore philosophy; you don’t waste cash on issues that make the product costlier and that almost all of patrons aren’t going to make use of.”

“Commodore has at all times paid lip service to software program,” Charpentier stated. “They do sufficient to get by after which depend on exterior sources to fill the hole. Commodore was an extension of Jack Tramiel, and to him software program wasn’t tangible—you couldn’t maintain it, really feel it, or contact it—so it wasn’t price spending cash for.”

The C-64 designers had plans of their very own for modifications which haven’t but been applied. They used the VIC-20 case to shortcut improvement, however they did have a brand new case designed that they meant to substitute in eight to 10 months. “It was thinner in entrance and had extra of a wedge form to it,” stated Charpentier. “I at all times thought the VIC-20 case appeared clunky.” A couple of new options have been additionally to be added to the machine.

The truth that these modifications haven’t been made has probably not affected the success of the C-64, asserted Brian Dougherty, president of the Berkeley Softworks of Berkeley, Calif. “This machine has the perfect graphics-display functionality of something that has but been performed for a TV display,” he stated. “It got here sloe to being an superior system.”

​The albatross of the C-64: its disk drive

The one main flaw of the C-64 just isn’t the machine itself, however in its disk drive. With a fairly quick disk drive and an sufficient disk-operating system (DOS), the C-64 might compete within the enterprise market with the Apple and maybe with different enterprise computer systems. With the current disk drive, although, it’s hard-pressed to lose its picture as a toy.

“Enterprise-oriented software program doesn’t look pretty much as good because it ought to on the C-64,” stated Dougherty, “not as a result of the bottom system isn’t ok however as a result of the disk-drive entry is just too sluggish; any enterprise utility requires loads of disk entry.” And for the reason that DOS is so weak and lacks options equivalent to the automated creating and sustaining of directories and maintaining observe of information, “it’s much more troublesome to develop enterprise software program” for the C-64, he added. “Any person like Lotus [Development Corp., manufacturer of a popular integrated business-software package] is dealing with much more problem than they did creating software program for the IBM PC, as a result of the PC has an operating-system construction that simply doesn’t exist for this product.

“The essential input-output system in ROM is finished pretty cleanly, in accordance with operating-system ideas. All of the routines that must be there are there, however there also needs to be a facility for mechanically studying the primary observe of the disk and booting a extra refined working system into reminiscence.”

The disk drive does actually have a facility for mechanically studying the primary observe of a disk, in accordance with Nelson of Epyx, however as a result of it isn’t documented, it isn’t broadly used.

How did the Commodore engineers botch up the disk drive?

“The disk drive? What a gory story!”

“The disk drive? What a gory story!” Charpentier stated. “That needed to do with the one advertising enter we did settle for. Advertising and marketing stated the C-64 needed to be appropriate with the VIC-20.”

The disk drive on the VIC-20, Charpentier defined, was a direct descendant of the drive on the Commodore Pet pc. “We had a parallel IEEE-488 bus for the Pet disk drive; and we used an odd format within the early days so as to pack information: on the outer tracks, the disk strikes quicker than on the interior tracks, so the info price modifications so as to pack extra information on the market. It was a pleasant thought, nevertheless it was clumsy, in that you just’re incompatible with everybody else. That’s the nut this all began with.”

The VIC-20 disk drive was designed in Japan, and the bus was modified from parallel to serial to economize. The drive could be very sluggish as a result of the serial-interface portion of the interface controller (the 6522) used on the VIC-20 doesn’t work. Consequently, the 6502 processor sends out one bit at a time below direct software program management, quite than sending a byte to the peripheral controller and letting it maintain clocks, information, and hand shaking.

“We mounted the serial-shift register for the 6526 [the interface controller used on the C-64 to replace the 6522] however we couldn’t use it, as a result of the disk drive needed to be appropriate,” Charpentier continued. “And, as a result of the processor within the C-64is turned off for 40 microseconds each 512 microseconds, it saved lacking the interrupt alerts that management the disk interface. The answer: sluggish the drive down even additional.”

Velocity was the one issue that would have been modified with out incurring the price of radical modifications within the disk drive; if the C-64 designers had been capable of forgo VIC-20 compatibility, they may have performed a lot better. And in the long run, after all, the C-64 was not appropriate with the disk drive of the IC-20 anyway.

“All of it stemmed from the 6522 serial interface not working,” Charpentier concluded.

Different producers are attempting to resolve the disk-drive downside of the C-64. Some are promoting their very own disk drives to be used with the C-64, however they’ve discovered it troublesome to interrupt right into a market that Commodore controls. Others are promoting applications that may be loaded into RAM to hurry up disk-transfer charges, however this selection applies solely to make use of of the C-64 for programming in Primary; prepackaged software program loaded into the system knocks the applications out of RAM. Epyx has launched a ROM-based program to hurry disk switch fivefold. In keeping with Nelson, this system will work with any disk-based software program. “That’s doable,” stated Charpentier. “The C-64 disk drive has its personal microprocessor and reminiscence, and you’ll ship info to it to alter the working system and to hurry up the serial-bus protocol.”

The usual software program for the C-64 disk drive can learn a 256-byte sector each 2.5 revolutions of the disk, or 512 byes per second. Programming methods utilized by Epyx have yielded switch charges of as much as 2.5 kilobytes per second. (Amongst different sluggish disk drives, Atari’s 810 transfers 1000 bytes per second, and the Apple II disk drive runs at a most of 15,000 bytes per second.)

Intelligent design shaves pennies

The Commodore group had labored arduous to make sure a low preliminary manufacturing price for the C-64. Vertical integration helped preserve elements prices down, and Winterble vetoed concepts for added options. The designers themselves believed in counting pennies; Charpentier stated he had discovered so much” from Jack Tramiel, who was “an actual stickler for price. We agonized over each transistor.”

With a manufacturing price of $135 and a retail worth of $595 at its introduction, the Commodore 64 would have a retail markup comfortably above the trade normal of 1 to 3 (maybe one to 2 when volumes climb). However Commodore has continued to seek out methods to scale back each the retail worth, now $149, and the manufacturing price, believed to be between $35 and $50 right this moment.

Commodore wouldn’t verify this price determine. Dougherty of the Berkeley Softworks estimated the prices of C-64 elements, base don his expertise at Mattel and Imagic.

  • Three ROMS at $1 every.
  • Eight dynamic Rams at $1.85 every.
  • SID (sound) chip and VIC (graphics) chip at $4 every.
  • RF modulator package deal, $3
  • 6510 microprocessor, $1 to $2
  • A handful of TTL, buffers, energy regulators, and capacitors for a complete of $5
  • Keyboard, lower than $10
  • PC board, $1 to $2
  • Plastic case, $1 to $2
  • Energy provide and miscellaneous connectors, $5 to $10
  • Packaging and guide, $1 to $2

In additional cost-cutting strikes, Commodore has changed the TTL with cheaper customized chips and has discovered methods to extend yields on the sound and graphics chips.

Not all cost-cutting steps have been with out detrimental impact on the system. The 6567 video chip was initially packaged in ceramic, although plastic is less expensive. “We tried all types of issues,“ Charpentier stated, “copper-lead frames, steel inserts within the package deal, and an ungodly variety of different issues to get a plastic package deal, as a result of a ceramic package deal could be very costly. However we couldn’t discover a package deal that ran cool sufficient. Earlier than I left Commodore, I listed some concepts to scale back the ability, however half of the chip was nonetheless working at an 8-MHzclip. And not using a main redesign, you can not get the ability out.”

The design group was autonomous—they did their very own market analysis, developed their very own specs, and took their child proper up by way of manufacturing.

The chip is now encased in plastic. Commodore engineers stated that along with redesigning the chip, they’ve developed a plastic package deal that may dissipate warmth in addition to ceramic.

For the reason that change to plastic packaging, a lot of new issues with the C-64 have been reported—issues which can be machine-specific or temperature-dependent. One failing that’s broadly recognized all through the software program trade is a bent for the chip to lock up when a program switches graphics modes—from displaying a bit map to displaying characters [see sidebar, “A Rich Collection of Graphics Modes”]. “A sport we have been producing began to fail on the manufacturing line,” stated Nelson of Epyx. “Then we’d take a look at [defective disks] once more they usually’d work. It trusted which machine we put them on and what the temperature was.” Charpentier speculated that some circuit traces had been left floating within the unique design; poor processing and excessive working temperatures would stress chips to the failure level.

One other downside that has begun to emerge in some C-64s is defective horizontal scrolling of bit-mapped screens. In a current overview of the Summer season Video games, an Epyx sports activities sport for the C-64, the San Jose, Calif., Mercury Information criticized the “flashbulb impact” noticeable throughout the swimming occasion. That, in accordance with Nelson, just isn’t an “impact”—the C-64 utilized by the Mercury Information reviewer merely doesn’t do horizontal scrolling correctly.

The liberty ended

Though the machine has its flaws, the designers of the Commodore 64 imagine they got here up with many important advances due to the liberty they loved throughout the early phases of the challenge. The design group was autonomous—they did their very own market analysis, developed their very own specs, and took their child proper up by way of manufacturing. However as quickly because the manufacturing bugs have been labored out and Commodore knew it had a winner, the company forms, which till then had been on the West Coast coping with the VIC-20 and the Pet pc, moved in.

“At that time, many advertising teams have been coming in to ‘assist’ us,” Winterble recalled. “The subsequent product definition was going to be thought up by one group, and one other group was to be liable for getting issues into manufacturing, and Al’s group would do R&D on chips solely.”

“Should you let advertising become involved with product definition, you’ll by no means get it performed rapidly,” Yannes stated. “And also you squander the power to make one thing distinctive, as a result of advertising at all times desires a product appropriate with one thing else.”

Charpentier summed up their frustration: “While you get many individuals concerned in a challenge, all you find yourself doing is justifying your self. I knew the Commodore 64 was technically pretty much as good and as low-cost as any product that may very well be made on the time, however now I needed to take heed to advertising folks saying, ‘It received’t promote as a result of it doesn’t have this, it could actually’t try this.’

“The liberty that allowed us to do the C-64 challenge will in all probability by no means exist once more in that surroundings.”

​Postscript (as of March 1985)

Of the unique Commodore 64 design group, solely Robert Russell stays at Commodore; he’s at present a design supervisor. The remainder of the group—Albert Charpentier, Robert Yannes, and Charles Winterble, together with David Ziembicki and Bruce Crocket, who helped debug the challenge and produce it into manufacturing—left Commodore within the spring of 1983 and shaped the corporate Peripheral Visions. Their plan was to design one other pc. To acquire working capital, they took on a contract from Atari—to design a keyboard for the Video Pc System, which was previewed however then, because the videogame market crashed, by no means launched. Peripheral Visions was sued by Commodore, which stated the VCS keyboard was a challenge that belonged to Commodore. At this writing, the swimsuit had not been resolved.

Peripheral Visions has been renamed Ensoniq and can quickly launch its first product, a music synthesizer. Albert Charpentier is at present vp of engineering at Ensoniq, Bob Yannes is senior designer, and David Ziembicki is supervisor of manufacturing management. Charles Winterble left Peripheral Visions and is now group vp of electronics at Coleco Industries Inc. of West Hartford, Conn. And Jack Tramiel is at present chief government officer of Atari Corp., the corporate that was Commodore’s chief competitor within the home-computer market earlier than dropping almost a billion {dollars} in competing towards the C-64.

To probe additional

Pc bookstores carry a wide array of books on the C-64. Amongst these really helpful are
What’s actually contained in the Commodore 64, by Bilton Bathurst, revealed by DataCap of Feneur, Belgium, and The Anatomy of the 1541 disk drive, by Lothar Englisch and Norbert Szczepanowski, revealed by Abacus Software program of Grand Rapids, Mich. Pc magazines equivalent to Artistic Computing and Compute! overview software program and publish applications that run on the C-64. The Commodore 64 itself could be discovered at most giant retailers.

How Programmers Exploited the C-64 {Hardware} (Slideshow)


A Synthesizer on a Chip

“I’d labored with synthesizers, and I needed a chip that was a music synthesizer,” stated Robert Yannes, the sound-chip designer and programs architect for the Commodore 64. He started engaged on the chip within the spring of 1981, assisted by two draftsmen and one CAD operator. “No one else had a good suggestion of what we have been doing,” he stated. “Past primary analysis, which I’d been doing since highschool, the precise design took solely about 4 or 5 months.”

The key variations between his chip and the everyday videogame sound chips, Yannes defined, have been its extra exact frequency management and its unbiased envelope for shaping the depth of a sound. “With many of the sound results in video games, there’s both full quantity or no quantity in any respect. That basically makes music unimaginable. There’s no technique to simulate the sound of any instrument even vaguely with that sort of envelope, besides perhaps an organ.”

Though it’s theoretically doable to make use of the amount controls on different sound chips to form the envelope of a sound, only a few programmers had ever tackled such a posh process. To make sound shaping straightforward, Yannes put the envelope controls in {hardware}: one register for every voice to find out how rapidly a sound builds up; two to find out the extent at which the word is sustained and how briskly it reaches that stage; and one to find out how briskly the word dies away. “It took a very long time for folks to know this,” he concluded.

Yannes additionally put a lookup desk within the {hardware} to transform information from musical notes to the equal frequencies, however that required extreme silicon. “I took that out,” stated Charles Winterble, who was worldwide-engineering director at Commodore throughout the C-64 design.

The exact capabilities of the sound chip should not clear even right this moment, largely due to incorrect specs having been written when the chip was first designed. “The spec sheet bought distributed and copied and rewritten by varied folks till it made virtually no sense anymore,” stated Yannes. An instance of the defective documentation is the declare that the chip can logically AND a number of waveforms. The chip can produce both a triangular wave, a sawtooth, or a sq. wave, relying on which bit is ready in one among its management registers. “There isn’t a interlock to guarantee that if one bit is on, the others are off,” Yannes stated. “That might have taken an excessive amount of silicon.” So if a couple of waveform is elected, the inner notes of the output multiplexer are discharged, and what emerges is the minimal of amplitudes.

One other error within the spec sheet issues the on-chip filters. “The filter was the very last thing that was labored on,” Yannes acknowledged. “I ran out of time. The pc simulation stated, ‘This won’t work very nicely’—and it didn’t.” The filter could have been mediocre, however the equations describing the way it labored have been simply plain incorrect, Yannes remembers. “They didn’t hold collectively. Nobody gave me an opportunity to appropriate them.”

Confronted by these incorrect equations, most software program designers use solely the sound chip.

A few of the Japanese programmers who wrote early sport software program for the C-64 took a distinct strategy, Yannes famous: “They wrote it in accordance with the spec. It didn’t matter to them whether or not one thing labored or not. Consequently, applications made sound results you couldn’t hear.”

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