Apple 1

From: Ethan Dicks <erd_at_infinet.com>
Date: Sun Dec 27 10:19:55 1998

>
> >On Sat, 26 Dec 1998, Jim Weiler wrote:
> >
> >> I've
> >> got a number of the early MC68000 (gold & ceramic) chips that would have
> >> been used in this circuitry. -Jim Weiler

As has been pointed out, Apples used the 6502 (or descendents). On the 68K
topic, I used to work for a company that made intellegent (synchronous) serial
cards for PDP-11 and VAXen. My former boss still has XC68000 S/N 424. The
very first run was hand numbered; we were told that 1-400 were for in-house
Motorola projects. We only got one because our company was so persistent
to the sales office that they shipped us a chip to shut us up.

The fun part is that the chip has bugs. Some of the instructions (I don't
know which ones) cause a microcode exception and the processor restarts
the microcode engine, resulting in delays of several microseconds. The
instruction completes, but not in the advertised number of machine cycles.
This wasn't a real problem for us, but some early 68K designs borrowed
heavily from existing Z-80 designs, including processor driven DRAM refresh.
These boards just lost the contents of memory whenever certain instructions
were executed. We had 32K of 2114 1Kx4 SRAMs. Our board performed oddly,
but it still worked. AFAIK, all MC68000 chips work to spec.

Anyone want to buy a vintage 1982, gold and ceramic Motorola MC68000? Make
offer. Not available in stores. Not found on eBay.

-ethan
Received on Sun Dec 27 1998 - 10:19:55 GMT