[Much useful stuff by Robin Whittle snipped]

>I would have said that MMX is of absolutely no interest to
>Csounders.  It is integer operations only - and usually several
>operands in parallel.  However, the benchmarks above indicate that
>the chips with MMX do actually perform floating point faster - even 
>though these benchmarks will not touch the MMX instructions.

Yes indeed, having done some digging around of my own, it looks very much
like MMX is a non-issue for Csound. In practice these CPUs can perform
either floating point OR MMX instructions, and need a 50 cycle context
switch to change between one mode and the other. 'Nuff said, I think.

However - the MMX CPUs have been optimised in other ways, including
improved branch prediction, which is why they are slightly faster than the
original Pentium chips.

Also, MMX2, due out late '97 or '98 will include FP opcodes. MMX 1 includes
a DSP style MAC opcode. A floating point MAC might - if Intel do it right -
make FFTs much quicker.

In the short term, another option to look at is AMD's new K6 chip. This is
pin compatible with most existing Pentium MBs, and will be available in
200MHz, 233MHz and 266MHz versions. It should be cheaper than either the
Pentium II or the existing Pentium Pros. (Except for the 150MHz, which
Intel are keen to dump now as it hasn't been a big seller for them.)

Although the K6 FPU isn't as speedy as that of the Pentiums, it's easy to
overclock this chip, and so it should be possible to get the 266MHz version
to run just short of 300Mhz. At that speed it should outrun a PPro 200
without breaking into a sweat. And for those that care about these things,
it also includes MMX. Apart from the weaker floating point performance,
it's a very fast chip indeed and is beginning to scare Intel very seriously.

A summary:

Pentium II - is a less than elegant piece of design. Its heatsink is so
heavy it has been known to fall out of its socket, and even then it runs
too hot to touch. It needs a whole new kind of motherboard because it uses
a slot instead of a ZIF socket. The performance doesn't seem to be anything
special, because the L2 cache is no longer on-chip. It does MMX. New
motherboards are likely to use non-SIMM RAM, which could be a big problem
for anyone who has invested in SIMMs. And it's going to be expensive too. 

Pentium Pro - likely to be sold off cheap later in the year, because Intel
want to kill off this chip. It's too expensive to make and it's not earning
them enough money. If you don't care about MMX, there will probably be some
bargains later in the year. My guess is PPro 200s will be down to the price
of the 150 by Q3 this year.

AMD K6 - well worth watching, especially when AMD settle their prices. The
overclocked 266MHz version could be quite something.

On that basis I've decided to wait till the Summer to see what develops.
Personally I'd be wary of investing in a PPro 150 right now, even given the
reasonable price, as I suspect there will be some better options available
within a few months. 

For a non-Intel perspective it's well worth looking at:

http://sysdoc.pair.com

which contains a lot of information about Intel systems and system
components, compiled by an independent outsider. 

R.