[geeks] Microsoft Surface...

[nate at portents.com]

>> ISTR that due to pipeline stalls or some other architectural issue,
>> multi-tasking OSes could not get the full performance out of the CPU.

Correct.  Context switching was prohibitively expensive.

> Never heard that myself.  Even so, it would have had to utterly cripple
> the performance of the processor even to just bring the i860's
> performance down into the ballpark with the i386 and i486 processors
> that were current at the time.  Intel's i860 prototype machine blew the
> latest, greatest i486 machines so far into the weeds it was ridiculous.
>  If memory serves, the *fastest* i486 at the time was 20MHz, and the
> i860 *started* at 100MHz.

The i860 is a great architecture on paper, not so great in practice.  It's
not unlike Itanium, it's VLIW cousin, in that they both put all the
pipelining work on the compiler at compile time, rather than have
dedicated on-chip circuitry to handle it at runtime.

The i860 didn't start at 100Mhz either, it started at 25Mhz.

Wikipedia's page on the processor is fairly comprehensive:

http://en.wikipedia.org/wiki/Intel_i860

- Nate