Xah Lee's Unixism

[red floyd]

Rupert Pigott wrote:

> It was specifically the 68000. Fixes were made that took effect in the
> 68010 and 68020. Dunno about 68008. IIRC the problem was that you could
> not restart some instructions properly. Some UNIX workstations did use
> 68Ks, there was an Apollo that had two of them running in lock-step,
> with one of them one instruction behind the other. When the leading CPU
> barfed, action would be taken and the other CPU would take over. Someone
> in comp.arch worked on the Fortune boxes and IIRC he claimed they had a
> more elegant single CPU solution.

68000 - original
68010 - 68000 + SR access is privileged, CCR is unpriviliated + 
instruction restart for VM access
68008 -- 68000 with 8 bit external data bus, possibly restricted address 
bus (can't remember)
68020 -- 68010 + full 32-bit
68030 -- 68020 + MMU