Wanted: iAPX-432

From: Jim Battle <frustum_at_pacbell.net>
Date: Wed May 23 23:00:32 2001

At 09:25 AM 5/23/01 -0600, emanuel stiebler wrote:
>Eric Dittman wrote:
>
> > all the delays. I could be completely off, but didn't some
> > of the processor features get implemented in the i860?

No. Maybe you are thinking about the i960? I dunno about that one, but it
was a lot more CISC than the i860. BTW, intel is coming out with a net
chipset that is called 860, but it is completely unrelated to the i860
processor.

>Yes. Was slow too ;-)

Hey, now. I've actually used an i860. A 3D graphics terminal I worked on
in 91-93 used two: one for the control processor, one for the geometry unit
(actually, we had the option of using two for the geometry unit, for a
total of 3). For its time, it was the best deal around for doing floating
point. Getting the maximum rated performance out of it required a lot of
very careful hand scheduling of instructions, but that's true of most
processors. I also believe it was the first microprocessor that had more
than 1M transistors, though a lot of that was contained in the two
caches. It could dispatch two floating point ops per cycle, and that was
back in 1991.

The 860 had a few problems. The big one was that intel didn't know how to
position it. The second problem, which was slightly improved in a second
version of the chip (that ran at 50 MHz), was that recovering from
exceptions could be a bear. This hadn't really been thought through. I
didn't work on it, but I recall hearing that the reference routine provided
by intel ran a number of pages, and had to do things like check to see what
the next instruction was and recover differently depending on what it was
about to step into. In the worst case, it could take thousands of cycles
to get back to a running state.

I agree, intel has one butt-ugly architecture with the x86, but nobody in
their right minds can fault them for succeeding despite that. Given the
fact that they must live with the ugliness, their implementations are first
rate.

-----
Jim Battle == frustum_at_pacbell.net
Received on Wed May 23 2001 - 23:00:32 BST

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