Hello its blogging time once again and its vintage computer time again! And for this entry were taking a peripheral look at this lovely system, The Commodore 128.
Released in 1985, it was not only the last 8bit computer from Commodore, but it was also one of the last 8bit computers released. The Commodore 128 is a unique computer as it's really 3 computers in one, It's its own platform based on the MOS 8502 CPU clocked at 1-2 MHz displaying either in 40 columns or 80 columns, It's a Commodore 64 since it has built in backwards compatibility with it (Either by typing GO64 in BASIC, holding the Commodore key on power up, or inserting a C64 cartridge game), and A CP/M compatible machine with its own Zilog Z80A (or B) CPU clocked at 4 MHz.
To give it the widest range of compatibility, Commodore also sold the 1571 disk drive for the computer. The 1571 had many improvement over the C64 and VIC 20's 1541. Not only did it include DIP switches for setting the device number for multiple drive's, a double sided drive mechanism, auto boot capability, and faster disk speed, but it was also capable of reading MFM formatted disks along side Commodore's own GCR formatted disks. The MFM reading capability allowed it to read the CP/M disks from machines like the Osborne 1 (with the double density upgrade), The Kaypro II and IV, and the Epson QX10.
All you need to do is insert the included CP/M Boot Disk, then whatever CP/M program from any of those compatible machines, and it will read it.
But the thing is, by 1985, CP/M was on the way out in favor of MS-DOS. So why did the 128 come with CP/M? According to Bill Herd, The engineer at Commodore responsible for creating the C128, he said that they included it simply for the heck of it, as well as something that could take advantage of the 80 column display immediately.
However, Commodore was aware that MS DOS was becoming more standard in the business world than CP/M, and being that they were interested in targeting the business market, they knew there would be a demand for MS DOS in that market. That's where the C128 MS-DOS Cartridge comes into play released in 1986 for $599.
Inside the device is quite simple, there's A MOS 8726 controller chip (Which also contains the BIOS) and an Intel 8086 CPU Clocking at 8 MHz.
Operation is also pretty simple. Just insert it into the cartridge port, put the C128 into 80 column mode, Insert the MS-DOS disk and it just reads it. It has the ability to use the C128's keyboard as your standard XT Keyboard of the era, but there was also a version with an XT/AT Keyboard connector as well. Much like the the Tandy 1000, it can use existing commodore peripherals in place of IBM ones, In fact the 1571 is used for reading and writing disks. It boots into a green text display by default (Mimicing the IBM 5151) but can still run games and applications in CGA Graphics. Luckily VICE has support for it so we can have a look at it.
April Fools!
Yep, I've been messing with you guys the whole time! Unfortunately there is no such thing as a C128 MS-DOS Cartridge, However, like any good lie, there is some truth rapped in it. For one thing the C128 and all the REU's are real (Obviously!), In fact the "C128 MS-DOS Cartridge" is actually just a 1750 REU Photoshoped:
Also the PCB is just the PCB of a 1750, The MOS 8726 "controller/BIOS chip" is actually the RAM Expansion Controller (Or REC), and the CPU socket is just a photoshoped version of the DIP socket already on the board.
In reality Commodore DID make a CP/M Cartridge for the Commodore 64 back in 1982.
This did pretty much exactly what you would think it would do, It contained a Zilog Z80 CPU to allow the C64 to run CP/M software.
The problem was, the C64 was stuck using the standard 1541, so it couldn't read CP/M disks. Combined with the fact that disk formats were not standardized on CP/M machines meant that software would have to have been made specifically for the C64 which software companies were unwilling to do, and unlike the Apple II equipped with the Microsoft Softcard, it was difficult for users to transfer CP/M programs to 1541 disks.
Its also true that Commodore were indeed thinking about MS-DOS compatibles at this point which I also referenced on that fake PCB, as I used a specific brand of CPU for it, Its a 8086 by Siemens.
The reason I chose this CPU from the German company with a very immaturely amusing name, is because Commodore used it in their own IBM compatible computer, the Commodore PC-10.
Yes, Commodore used to make IBM compatibles, In fact, in that video demonstration I was using PCem to emulate the Commodore PC 30-III from 1987.
This is something Ill come back to in my next entry, In the end although the C128 MS-DOS cartridge doesn't exist, I still feel it could be possible. The C128 does have RGBI output from a chip that is like the 6845, it can read MS-DOS formatted disks, and it probably could even emulate the PC Speaker through the user port like the PET did for its sound output, and hey, If a device like the Mimic Systems Spartan exists that can allow a C64 to become a full fledged Apple II, why cant the same thing be done with the IBM PC and the C128?
But I still feel like it would require a lot of engineering workarounds due to the C128's design. In the End, after telling some misinformation for a joke, I feel like I should rectify this by doing what I do best, Telling factual information for real! But until then, Happy April Fools Day, and as always, Thanks for reading! See you next time!
No comments:
Post a Comment