cclist at sydex.com
Sat Jul 4 12:06:16 CDT 2015
On 07/04/2015 09:42 AM, Diane Bruce wrote:
> Both Apollo and SUN did this. The clocks were two phase so one ran
> behind the other. It was a hack.
I don't remember when I first saw the 68000 in detail--perhaps it was at
a WESCON in the late 70s. My 68K manual is from that show and I took
some time to actually sit down and read the first couple of chapters at
the show. The mention of a supervisor mode and faulting on undefined
addresses (bus faults, actually) got me very excited and immediately
sent visions of virtual memory spinning.
I went back to the guy at the Motorola sales booth and asked him about
the prospect. He sighed and rolled his eyes a bit and said that I must
have been the hundredth person to ask about the subject that day. He
did his best to gently break it to me that not all instructions could be
restarted from a bus fault--the CPU simply didn't save enough
information to make that possible.
The following year, there were a number of Unix boxes being shown that
used the 68K, advertising that they were real competition for
traditional minis. Against my better judgment, it was decided that the
the system to supplement our VAX 11/750 setup would be a Plexus box.
That was a mistake, as I predicted. The box became the butt of jokes
about its lack of performance.
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