The Commodore 128: The Most Versatile 8-Bit Computer Ever Made
by Ian Matthews of July 11 2003
Last Revised Dec 30 2018

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Commodore 128 History:
In the summer of 1984 Commodore decided that they needed a replacement for the amazingly successful C64. More accurately they decided that the TED / 116 / Plus/4 / 264 Series was a failure as a replacement for the C64.

This machine would be Commodores last 8-Bit computer; after this they would produce only 16/32 Bit Amiga’s and IBM PC clones.

Customer reaction to Commodores failure to provide native CP/M support in the C64 and (much worse) their failure to provide C64 compatibility in the Plus/4 / 264 Series taught Commodore engineers some hard lessons. Commodore’s founder and visionary, Jack Tramiel, had quit months earlier and the new management team wanted to just forget the Plus/4 / 264 Series fiasco. Fortunately, the engineers knew they needed a new product and that product had better be compatible with the best selling computer in the world, the C64.

Bil Herd got the top job as128 lead Engineer because of his vocal criticism of the new management teams lack of vision. “No one dreamed that C64 compatibility was possible so, no one thought along those lines. I had decided to make the next machine compatible with _something_ instead of yet another incompatible CBM machine. (I won’t go into the “yes Virginia there is Compatibility” memo that I wrote that had the lawyers many years later still chuckling, suffice it to say I made some fairly brash statements regarding my opinion of product strategy). Consequently, I was allowed/forced to put my money where my mouth was and I took over the C128 project.”

bil_hurd_xmas_2003Under managements guidance, the first C128 concept machines (pre-prototype) made no attempt at C64 compatibility. Bil recalls, “I looked at the existing schematics once and then started with a new design based on C64ness. The manager of the chip group approached me and said they had a color version of the 6845 if I was interested in using it would definitely be done in time having been worked on already for a year and a half… And so the story begins.”

Commodore needed its next computer to be a serious upgrade from the C64 if it was to successfully battle its arch nemesis; it needed to keep Jack Tramiel’s, Atari, from besting them with features in the their rumored new “ST” line.

In 1982, Commodore released the worlds first multi-processor personal computer, called SuperPET, but it was $2800 ($6100 dollars in 2018) and targeted at the education / scientific markets. The Commodore 128 was to be the worlds first mass market multi-processor computer. It would also have two video subsystems, one of which would allow it to connect to a TV.

A reviewer from Your Computer magazine wrote “The dowdy shoebox image of the Commodore 64 has been replaced by a slim line beige console that any style-conscious businessman should be pleased to have on his desk. A full size typewriter style keyboard has 92 keys, that travel and locate well.” The 128’s 80 column display mode would produce 640×200 which was better than the CGA mode that IBM PC’s could produce even in the early 1990’s! This new an powerful machine would act as three completely separate computers in one:

Commodore 128 Mode 2Mhz Speed (8502 CPU), 128K Memory, very nice 80×25 RGB display, advanced Basic 7.0
Commodore 64 Mode 1Mhz Speed (6510 emulation in the 8502 CPU), 99.8% compatible with 64 hardware and software, accessed by booting the machine while holding down the Commodore key or typing GO 64
Commodore CP/M Mode 1-4Mhz Speed (Zilog Z-80 CPU), 100% compatible with the huge volume of CP/M business applications such as Turbo Pascal and WordStar (an excellent program I used personally for years on a Sanyo MBC555 !) Note that the Z-80 processor was originally spec’d by Commodore management to be the same external expansion cartridge used on the C64. However, to resolve several other engineering problems, Bil Herd designed the Z-80 into the main board. This mode required CP/M software disks to be loaded on boot up.
All this would sell for an initial price of just $300 ($650 in 2018 dollars); half of the Commodore 64 price when it was introduced two years earlier.

The Chips:
MOS 8502 CPU – Yet another derivative of the 6500 series
Zilog Z-80 Improved version of Intel 8080 CPU designed by the same Intel engineer
MOS 8563 CRCT / VDC – Video Display Chip 80 column x 25 rows 640×200 (128 mode only)
MOS 8564/6 VIC – Video Interface Chip (NTSC / PAL) – used in 40 column x 25 row
MOS 8722 MMU – Memory Management Unit
MOS 6581 SID – Sound Interface Chip
MOS 6526 CIA – Complex Interface Adaptors (2 of them!)
Commodore 128 in 80 Column Mode

This technically complex machine would present serious engineering and marketing challenges to any company. Bil Herd recalls “It was sometime in September (1984) when we got 8563 (new 40/80 column color video chip) Silicon, good enough to stick in a system. …One concern we had was it occasionally blew up…. big time…. turn over die and then smell bad….. But then all of the C128 prototypes did that on a semi regular basis as there wasn’t really any custom silicon yet, just big circuit boards plugged in where custom chips would later go… but you can’t wait for a system to be completed before starting software development. When this problem still existed on Rev 4 we got concerned. It was at this time that the single most scariest statement came out of the IC Design section in charge of the ’63. This statement amounted to ‘you’ll always have some chance statistically that any read or write cycle will fail due to (synchronicity)’ “.

“Synchronicity problems occur when two devices run off of two separate clocks, the VIC chip hence the rest of the system, runs off of a 14.318Mhz crystal and the 8563 runs off of a 16Mhz Oscillator. Now picture walking towards a revolving door with your arms full of packages and not looking up before launching yourself into the doorway. You may get through unscathed if your timing was accidentally just right, or you may fumble through losing some packages (synonymous to losing Data) in the process or if things REALLY foul up some of the packages may make it through and you’re left stranded on the other side of the door (synonymous to a completely blown write cycle). What I didn’t realize that he meant was that since there’s always a chance for a bad cycle to slip through, he didn’t take even the most rudimentary protection against bad synchronizing. …As it turns out the 8563 instead of failing every 3 years or so (VERY livable by Commodore standards) it failed about 3 times a second.”

In addition the yield on these video chips was about .001%. Commodores chip division MOS Technologies could only get three or four working chips the per run. “A run is a half-Lot at MOS and costs between $40,000 and $120,000 to run. Pretty expensive couple of chips.”

As if these problems were not enough, the power supply needed to be adjusted for each chip or they would literally burn up. “No single custom chip was working completely as we went into December (1984) with the possible exception of the 8510 CPU… At this point all I did have to lose was a HUGE jar of bad 8563’s. (One night a sign in my handwriting “appeared” on this jar asking “Guess how many working 8563’s there are in the jar and win a prize.” Of course if the number you guessed was a positive real number you were wrong.)”

consumer-electronics-show-registration-1983With only five or six weeks to go until the January Consumer Electronics Show in Vegas “…finger pointing was in High swing, (the systems guys should have said they wanted WORKING silicon) with one department pitted against the other, which was sad because the other hardworking chip designers had preformed small miracles in getting their stuff done on time… …Managers started getting that look rabbits get in the headlights of onrushing Mack trucks, some started drinking, some reading poetry aloud and the worst were commonly seen doing both. Our favorite behavior was where they hid in their offices. It was rumored that the potted plant in the lobby was in line for one of the key middle management positions.”

Unbelievably, in this time of crisis, both MOS chip designers went on Christmas vacation and “…a sprinkler head busted and rained all over computer equipment stored in the hallway. Engineering gathered as a whole and watched on as a $100,000 worth of equipment became waterlogged…. I can honestly say that it didn’t seriously occur to me that we wouldn’t be ready for CES… here were just too many problems to stop and think what if.”

Von had wisely chosen not to try to follow all of the current Revs of the 8563, instead he latched onto a somewhat working Rev4 and kept if for software development. Later we would find out that Von, to make the 8563 work properly, was taking the little metal cup that came with his hot air popcorn popper (it was a buttercup to be exact) and would put an Ice cube in it and set it on the 8563. He got about 1/2 hour of operation per cube. On our side there was talk of rigging cans of cold spray with foot switches for the CES show.”

Bil Herd stated that a number of “odd engineering fixes”, often conceived after consuming a few beers at the bar beside the MOS factory, resulted in seemingly insurmountable problems being quickly resolved. The most important of these ‘fixes’ was the integration of a Z-80 CPU into the main board. In addition to resolving several taxing electronic problems, it elevated the C128 into the realm of the business computer. “A True Miracle and was accompanied by the sound of Hell Freezing over, the Rabbit getting the Trix, and several instances of Cats and Dogs sleeping together. This was the first time that making CES became a near possibility. We laughed, we cried, we got drunk.”

“We averaged 1-3 of these crises a day the last two weeks before CES. Several of us suffered withdrawal symptoms if the pressure laxed for even a few minutes. The contracted security guards accidentally started locking the door to one of the development labs during this time. A hole accidentally appeared in the wall allowing you to reach through and unlock it. They continued to lock it anyways even though the gaping hole stood silent witness to the ineffectiveness of trying to lock us out of our own lab during a critical design phase. We admired this singleness of purpose and considered changing professions.”

“We finished getting ready for CES about 2:00am in the morning of the day we were to leave at 6:00am.”

“Advertisements in the Las Vegas airport and again on a billboard en-route from the airport inform us that the C128 has craftily been designed to be expandable to 512K. Now it had been designed to be expandable originally and had been re-specified by management so as to not be expandable in case next year’s computer needed the expandability as the “New” reason to buy a Commodore computer. That’s like not putting brakes on this years model of car so that next year you can tote the New model as reducing those annoying head-on crashes.”

You can see in the advert to the right that a 512K expansion was eventually made, but not by Commodore. This was from Berkely Softworks in 1990!

"Upon arriving at the hotel we find that out hotel reservations have been canceled by someone who fits the description of an Atari employee. Three things occur in rapid succession. First I find the nearest person owning a credit card and briskly escort her to the desk were I rented a room for all available days, second, a phone call is placed to another nearby hotel canceling the room reservations for Jack Tramiel and company, third, several of those C64’s with built in monitors (C64DX’s??? man it’s been too long) are brought out and left laying around the hotel shift supervisors path accompanied by statements such as “My my, who left this nifty computer laying here… I’d bet they wouldn’t miss it too much”.

“The next day we meet up with the guy who developed CPM (Von) for the C128. As I mentioned earlier, someone forgot to tell him about the silly little ramifications of an 8563 bug. His ‘puter didn’t do it as he had stopped upgrading 8563s on his development machine somewhere around Rev 4 and the problem appeared somewhere around Rev 6. As Von didn’t carry all the machinery to do a CP/M rebuild to fix the bug in software, it looked like CP/M might not be show-able. One third of the booth’s design and advertising was based on showing CP/M. In TRUE Animal fashion Von sat down with a disk editor and found every occurrence of bad writes to the 8563 and hand patched them. Bear in mind that CP/M is stored with the bytes backwards in sectors that are stored themselves in reverse order. Also bear in mind that he could neither increase or decrease the number of instructions, he could only exchange them for different ones. Did I mention hand calculating the new checksums for the sectors? All this with a Disk Editor. I was impressed.”

“Everything else went pretty smooth, every (power) supply was adjusted at the last moment for best performance for that particular demo. …On the average, 2 almost working 8563’s would appear each day, hand carried by people coming to Vegas. Another crisis, no problem, this was getting too easy.”

The Peripherals:
Commodore did not produce many peripherals designed exclusively for the 128 line because they did no have to. They relied primarily on existing C64 devices like the 1541 floppy drive. An exception was the Commodore 1902 monitor for $400 (which is $875 in 2018 dollars and was $100 more than the price of a new C128!) which was required to use the new 128’s advanced 80 column mode. The C1750 massive 512K RAM Expander was another new product. The most anticipated new peripheral was the 1571 double sided floppy drive which, at 360K, provided more than double the capacity of the 1541. Much more importantly it was a whopping 7 to 10 times faster!

Many Bulletin Board Systems (BBS’s – pre-internet for those of you who were born after 1980) also jumped on the C128 Mode bandwagon. There are a number of historians who site Commodore as the unsung development partner of the Internet. While it is certainly true that the US military and several universities developed ARPANET, its transition into the internet would not have been so rapid had online communities not been created with extensive use of Commodore hardware: the amazingly inexpensive VIC Modem (and its decedents the 1600, 1650, 1670 and 1680) combined with powerful C128 Mode functionality allowed thousands of BBS’ to spring up from nothing. The 128 produced:

a large supply of online information
consumer awareness, which created demand, and
telecommunication capacity and skills
all of which are were required to develop and commercialization the Internet

The Commodore 128D:
In an effort to extend the life of this powerful multi-talented machine, Commodore introduced a slight derivative of the 128 called the Commodore 128D in 1987. The idea was to make a cleaner, smaller foot print for the 128 so that it might appeal to the small business segment dominated by IBM at the time. Commodore 128D models looked allot like Apple Mac computers of the late 1990’s. They came in a square desktop box, featuring an integrated a front loading Commodore 1571 5.14″ high capacity floppy disk drive, and a separate keyboard. A monitor could sit nicely on top of this chassis, again reducing desk space requirements and clutter. The price of this system, just $500 ($1100 in 2018 dollars), a third the price of an IBM PC.

In a cost saving effort, D’s were manufactured with less expensive “upgrade” versions of the SID (sound) chip, called the 8580 SID and were sometimes referred to a 128DCR’s (Cost Reduced).

The first European 128D’s chassis were made of plastic. They came with a keyboard dock and carry handle! The North American model came in standard beige steel chassis’ without the carry handle or keyboard dock.

On an amusing note, I have often been asked questions from non-Commodore collectors about a super-rare prototype called a Commodore 1280. Of course this is simply a misreading of the Commodore 128D name.

Today (in 2003), 128D models are highly sought after by collectors and enthusiasts, usually garnering more than triple what a standard 128 sells for.

The People of the Commodore 128:
Early in the process, a team of experienced hardware and software engineers were assembled and they left their personal mark on the their machine with an “easter egg”. Type SYS 32800,123,45,6 on your 128 and you will see a small list of development credits. Note the spelling of the word Hardware; presumably a tribute to Bil Herd. The image on the left was created with the amazing WinVice Commodore emulator available from many sources including download from download menu.

Bil Herd explains “The names of the people who worked on the PCB layout can be found on the bottom of every PCB.”

Bil Herd Original design and hardware team leader.
Dave Haynie Integration, timing analysis, and all those dirty jobs involving computer analysis which was something totally new for CBM.
Frank Palaia One of three people in the world who honestly knows how to make a Z80 and a 6502 live peacefully with each other in a synchronous, dual video controlled, time sliced, DRAM based system.
Fred Bowen Kernal and all system like things. Dangerous when cornered. Has been known to brandish common sense when trapped.
Terry Ryan Brought structure to Basic and got in trouble for it. Threatened with the loss of his job if he ever did anything that made as much sense again. Has been know to use cynicism in ways that violate most Nuclear Ban Treaties.
Von Ertwine CPM. Sacrificed his family’s popcorn maker in the search of a better machine.
Dave DiOrio VIC chip mods and IC team leader. Ruined the theory that most chip designers were from Pluto.
Victor MMU integration. Caused much dissention by being one of the nicest guys you’d ever meet.
Greg Berlin 1571 Disk Drive design. Originator of Berlin-Speak. I think of Greg every night. He separated my shoulder in a friendly brawl in a bar parking lot and I still cant sleep on that side.
Dave Siracusa 1571 Software. Aka “The Butcher”
Special note: “RIP: HERD, FISH, RUBINO”

“The syntax refers to an inside joke where we supposedly gave our lives in an effort to get the FCC production board done in time, after being informed just the week before by a middle manager that all the work on the C128 must stop as this project has gone on far too long. After the head of Engineering got back from his business trip and inquired as to why the C128 had been put on hold, the middle manger nimbly spoke expounding the virtues of getting right on the job immediately and someone else, _his_ boss perhaps, had made such an ill suited decision. The bottom line was we lived in the PCB layout area for the next several days. I slept there on an air-mattress or was otherwise available 24 hours a day to answer any layout questions. The computer room was so cold that the Egg McMuffins we bought the first day were still good 3 days later.”

The End of the Commodore 128:
The 128 went on to be a notable success for Commodore but not because of its new power. Unfortunately most software developers ignored the new and advanced C128 Mode functionality. Why develop software for a new, relatively small product like 128’s native mode when you can write software for the wildly successful C64 and know that your code will function on a 128 operating in 64 mode. There were some notable exceptions, such as the Graphical User Environment called GEOS which created a powerful 128 Mode version.

Before its demise in 1989, the Commodore 128 sold a respectable four million units but this number could have been dramatically larger. Much like the Amiga to come, Commodore was incapable of promoting the C128 to the appropriate target markets. 128’s were insanely inexpensive when compared feature for feature with its the competition of the day and in the end they sold about 10 times their nearest competitor, the Apple IIc. If Commodore had developed and pushed the “D” models to the small business market in 1986, the 128 could have been a serious contender in that space.

The last gasp was a very small production run Commodore 128CR’s (Cost Reduced) released in North America in 1988 or 1989. They were identical to the 128DCR except they did not have an integrated floppy drive. I have never seen one of these units… not even a picture! If you have one, please email a picture to us and we will add it to this site with credit to you.

On a sad note, the 128’s CP/M Mode was almost never used because CP/M was quickly losing ground to Microsoft Disk Operating System (MS DOS) by then running at version 2. MS-DOS was of course popularized by the IBM PC and seemingly endless line of IBM clone machines. Business developers had all but abandoned the old standby CP/M in favour of the new and rapidly expanding DOS market. The Commodore 128 was CP/M’s last big play, but the 128 just did not have the market penetration to keep CP/M alive.

The Commodore 128 was a pretty cool machine and as we mentioned in the article, it still has a serious following. When researching our November 2018 update of this page, we were pleased to here someone is working on a new C128 project.

There isn’t much information on 128RM but the graphics show it is “The 128 Remastered” and the forum thread for this indicates it is designed to fit into a Commodore 64 chassis.

In April 2016 the designer said “…I do not want to postpone the main chips (MOS chips) because I’m already at the 7th ‘Rebuilding from 0’, aka. ‘MK7’ (see the back of the board).” so whoever it is, he is serious. In October 2018 he wrote “To put it briefly: “THE128RM” is in the final version. 🙂 (I will certainly optimize this before the “release-version”). Currently I’m waiting for the manufacturer.”

In November 2018 he explained that the board will come with everything but the MOS chips “…no bare board. All components are on it. You just have to fill the sockets.” and few people on the forum are bouncing around prices ranging from 50€ to 200€ but the designer has not commented yet. Fortunately, he does have a website but, as of this writing, there is nothing on it but single picture and COMING SOON notice.

We contacted the designer at the end of November 2018 and Peter provided us with the pictures to the right (which are 1 version out of date) and told us:

I am currently waiting for the manufacturer to finish, hopefully the last version. I am thinking of to start the pre-order this year. Reseller’s are welcome! 🙂

I think we don’t have any legal issues. I am not using the Commodore brand name and using an modified version of the schematics. So there shouldn’t be any.

Beyond the 128RM, we also found some cool new hardware items on eBay. Most notably the Commodore 128 Diagnostic Cartridge. The seller describes it like this:

NEW V2 – Commodore 128 Diagnostic Cartridge 785260 GOLD ENIG C128 128D 128DCR in stunning black! This new Version 2 of our 128 diagnostic cartridge features a decoupling capacitor on board. It exists to filter undesired noise from your power supply.

This is uniquely designed specifically for the Commodore 128/128D/128DCR operating in 128 mode! That’s right, this diagnostic cartridge will test your 128 while operating in 128 mode… not 64 mode.

Commodore 128 Chronology:
Italicized lines refer to key moments in history that are not Commodore related
January 13th – Commodore shows off prototype 264 and 364 at CES and indicates they should be in production by June
January 15th – Commodores founder, visionary and CEO, Jack Tramiel quits Commodore with secret plans to buy the near bankrupt Atari
April – Commodore launches its first IBM clone, the Commodore PC, at the Hanover Fair in Germany
April – Commodore shows the Commodore Z8000 at the Hanover Fair in Germany
Mid-Summer – Commodore decides the Ted / 264 / 116 / Plus/4 Series will not sell as a replacement to the C64
September – Bil Herd appointed lead designer on C128 project in an effort to get a new machine ready for show at CES in Las Vegas, the 2nd week of January 1985
November – New chips are still not close to stable
December – Z-80 CPU incorporated into motherboard design – chip problems start getting resolved quickly
December – A 16K version of the 264 called the Commodore 116 is for sale (at least in Germany)
Intel introduces the 80186, 80188, and 80286 processors
Motorola unveils its 68010 CPU chip
January – The last VIC-20 rolls off the line and into the history books
January – Serious design problems still exist but are being resolve daily
January – C128 prototypes completed at 2am just 4 hours before the trip to CES
January – Commodore’s hotel rooms have been cancelled, possibly by their former boss turned competitor, Jack Tramiel
January – Prototypes shown at CES are unstable, going through two 8563 video chips per day, but the audience is unaware of this
Januray – Atari introduces the 130ST: 128KB RAM, 192KB ROM, 512 color graphics, MIDI interface, and mouse for $400.
January – Atari introduces the 520ST: 512KB RAM, 192KB ROM, 512 color graphics, MIDI interface, and mouse for $600.
June / July – C128 production begins and units are to sell for just $300
April – IBM stops production of the IBM PCjr
May – Microsoft demonstrates Microsoft Windows 1.0 at Spring Comdex. Release date is set for June, at a price of US$95
September – Apple Computer co-founder Steve Jobs resigns from Apple Computer and founds NeXT Incorporated
Commodore stops production of the 64 several times (presumably in favor of the much more powerful 128) but restarts it because of demand
January – Apple Computer starts producing the Macintosh Plus, with 1 MB RAM, support for hard drives, a new keyboard with cursor keys and numeric keypad, for $2600 ($5200 in 2018 dollars)
Design of the 128D, business style case with neatly integrated 1571 floppy disk drive begins
Germany celebrates its 1,000,000 C64 with a Golden Jubilee version
March – Microsoft goes on the stock market at $21 per share. This raises $61 million ($125 million in 2018 dollars).
June – In an effort to revitalize sales, Commodore releases a sleek new 128 like case, changes the name to 64C, and bundles it with GEOS
August – Intel ships the 80386
September – Plus/4 was in full liquidation were selling for a mere $79 ($160 in 2018 dollars)
September – IBM announces the IBM PC-XT Model 286, 640KB, 20MB hard drive, 1.2MB floppy, serial/parallel ports, and keyboard for the low low price of $4000 ($8100 in 2018 dollars)
128D’s hit retail stores in Europe and North America for about $500 ($950 in 2018 dollars)
February – Commodore announces the Amiga 500 and 2000
April – IBM and Microsoft announce Operating System/2 – OS/2.
June – Atari releases the Atari XE Game System, with 64KB RAM, supporting 256KB game cartridges
October – Microsoft ships Windows 2.0
Production of all 128 models stops
Total Commodore 128 sales are in the four million unit range about 10 times that of it’s nearest competitor the Apple IIc
Intel introduces the 80486 microprocessor at Spring Comdex in Chicago. It integrates the 80386, 80387 math coprocessor, and adds a primary cache. It uses 1.2 million transistors. Initial price is US$900 ($1600 in 2018 dollars)