[rescue] i860 Success

Francisco Javier Mesa-Martinez lefa at ucsc.edu
Sat May 1 17:25:46 CDT 2004

On Thu, 29 Apr 2004, Charles Shannon Hendrix wrote:

> The i960 was a re-design of the IA432, fixing the speed issues and was a
> decent general purpose CPU with an MMU and everything.
> Intel *marketing* "designed" it as an embedded CPU by removing the MMU
> and marketing it as an embedded processor.

Whaaaa? I never heard that, the 432 is one (if not the most) CISCiest
projects ever attempted, tons of Opcodes and HLL hardware support in
silicon. The 960 is pretty RISCy, I don't think it ever had an MMU, but I
am not sure about this. It was one of the earliest superscalar designs
too. As far as I know the 960 was a refinement from the sucessor of the
432, there is not much in common... except that the 960 is almost like an
anti-432, they dropped everything that made the 432 like the complex ISA,
the microcode, the tag support etc.

It was a fairly cheap, clean simple design and I assume it made it as an
embedded design because of those three factors. Plus intel did not want
anything to interfere with the x86, I believe the 960 was also developed
as a contract with the DoD for embedded processors.

The i860 was a completely different machine, it was supposed to be the
main competitor of the 88K series from motorola. Both chips were
introduced in '88 I believe and were supposed to take over from the early
RISC adopters. However the 860 was hard to code for because it had some
VLIW characteristics, i.e. it was very anal about the exact pairing of
instrcutions (and I believe it required explicit scheduling) to achieve
superscalar performance (int/fp single cycle issue). It had some neat
things like a very wide bus (64 bits, that is why a lot of people label
this as a 64-bit chip, but it is a 32-bit CPU in reality), a fairly
efficient FPU, and it had a dedicated 3D graphics unit. Almost like a
predecessor to the MMX in the Pentium. The 3D unit and the nifty FPU made
it an ideal choice for some bendors to use the board as a dedicated
geometry/raster co-processor. I believe SGI, DEC, IBM, NeXT, and a bunch
of other people marketed 3D boards based on the chip. I believe very few
vendors tried to use it as a general purpose CPU. Intel released a series
of Supercomputers based on it, Stardent made some workstations, Oki, and I
think Alliant also made a few minis based on this chip. But it was hard to
get anywhere near the quoted performance figures so it was never a popular

The i860 I think was the first million transistor CPU in the general
market. It was released at the same time as the 486 and with the same
number of transistors it got more than twice the performance than the x86
part. I think Intel's plan was to expect people to migrate to the 860
platform and leave the 486 as the last x86 iteration. We all know what
happened next.....

Think of it as a modern day Itanium, a pain in the neck to code for, and
even harder to get the performance Itel quotes in their benchmarks.

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