db at db.net
Sat Jul 4 13:16:07 CDT 2015
On Sat, Jul 04, 2015 at 10:06:16AM -0700, Chuck Guzis wrote:
> 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.
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).
- db at FreeBSD.org db at db.net http://www.db.net/~db
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