4 Jul
2015
4 Jul
'15
11:16 a.m.
On Sat, Jul 04, 2015 at 10:06:16AM -0700, Chuck Guzis wrote:
On 07/04/2015 09:42 AM, Diane Bruce wrote:
Sure, and the information they did push on the stack when they finally
added instruction continuation was pretty hefty. 68010 had that with
limited addressing (Which the MAC (ab)used).
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.
--Chuck
Diane
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