So Many Replicas!

[sje]

The S-100 bus had too many problems physically, electronically, and logically. That's why it died out so quickly. Designed for the 8080, and not very well at that, it is a piling of kludge upon kludge to make the S-100 bus work for a 6502, 65856, or 68000.

[Grant Stockly]

Originally Posted by sje

The S-100 bus had too many problems physically, electronically, and logically. That's why it died out so quickly. Designed for the 8080, and not very well at that, it is a piling of kludge upon kludge to make the S-100 bus work for a 6502, 65856, or 68000.

Its already enough of a stretch to throw a 68000 on an S-100 card and say "Altair runs Linux". It has to at least get power from the S-100 bus and make the lights blink!

Imagine it, with Linux the Altair would finally be Slashdot worthy.

[Grant Stockly]

I think it may be a 64 pin DIP, which is still better than a 68 pin PLCC.

[sje]

The Unicorn Electronics link is inviting, but I checked and all of their catalog pages are at least a year old. So maybe the stock counts are not really up to date.

If someone uses GPL code but never releases the product, then they're in the clear.

Until the advent of the fairly well specified PCI bus, all earlier microcomputer buses were either too slow, too big (VME), proprietary (IBM micro-channel), or just plain crap (S-100, ISA). The only exception is the MIT NuBus that was used in the early slot days of Macintosh computers, and even that bus was a little slow (33 MHz).

It would be possible to run Unix/Linux on a 4 KB 8080 with enough mass storage; simply write a small interpreter that's powerful enough to run an interpreter for a 68K or some other process, and have that interpreter run the OS and applications. Maybe it would be better to have 16 KB 8080 and only run one interpreter. I've heard of one Mac enthusiast who ran a PowerPC interpreter on an ancient 68K Mac and it boots OS/X. It runs a couple hundred times slower than the real thing.

[Grant Stockly]

The thought of Vista on an IBM PC or Mac OS X on a Lisa has crossed my mind.

[Grant Stockly]

Unicorn maintains a stock of any item on their website. They will sell you anything on there at that price. If they don't have it, they get it. They then will sell you one part.

They do not list 8008 microprocessors or Kenbak memory, but I have bought both. If you want a part they do not stock, then you have to buy a minimum of 25-100 parts.

[sje]

An early version of the Mac OS ran on a lightly modified Lisa; the product was called an Macintosh XL and included a hardware mod that changed the original oblong pixels to square pixels. Its 68000 ran at a blistering 5 MHz.

If you're serious about running a 68000 on an Altair bus, you might want to go with the somewhat castrated eight bit version of the chip, the 68008. Hard to find, though. Its address bus was cut from 24 to 20 bits while the data bus was cut in half from the original eight bits. I have a circuit for this, and let me tell you that you're going to have to hijack a few unused S-100 lines for getting the 68000 bus grant and DTACK scheme up and running. Also (and I may be wrong here, it's been a while), the 68008 was an NMOS design and had a minimum operating frequency requirement. Hopefully it is less than the 2 MHz upper limit of the rest of a typical S-1000 system.

I always had a fondness for the 68000 family, even though it really wasn't fully debugged until the 68030 (Integrated MMU) plus 68882 (FPU) combination. You see, I had learned Unix on a pdp-11/70 and the 68000 family is the logical 32 bit extension of the good parts of the pdp-11 CPU design. (Compare with the VAX-11 CPU that suffered a design by committee approach.)