OT Linux (RE: [rescue] OT: Stuffed Proliant?)

[Joshua D Boyd]

On Sat, Dec 22, 2001 at 12:01:00AM -0500, Ken Hansen wrote:
> MMX was not worthless, it was simply not worht the premium Intel got for the
> chips when new... The MMX CPU had a larger on-chip L1 cache than non-MMX
> CPUs. The usefulness of the new instructions was, of course, dubious, since
> most software was still being compiled for 486-class machines...

MMX was pretty much worthless, not MMX Pentium chips.  I didn't think that 
people were going to take it to mean MMX P5s versus regular P5s.

Assuming you took the time to optimize for MMX (instead of flagging the 
compiler for a 486), the benfits are still dubious since you can only work with
2 32bit ints at once (or 4 16bit ints).  Now, this means that if you build your
3D engine to use 16bit ints instead of 32 or 64bit floats, you have a good
performance boost.  But, the visual quality is going to be problematic,
especially if you value correctness for professional level work.  Similarly, 
you can get some benefit from 16bit audio processing, but really at a minimum
you should be using 32bit ints for processing, and preferably floats (for say
studio quality work).  

Now, in theory, you could use MMX pretty effectively for photoshop type apps 
without loosing to much.  Again, the ideal is for floats, but photoshop
doesn't use those for most  things to my understanding, and the quality doesn't
suffer too much for it.

So, MMX is really only decent for games and 2D imaging.  But wait, it gets 
worse.  With the advent of geometry acceleration on video cards, MMX no longer
gives us a meaningfull boost with 3D.  But, we still have to use floats for the
things that don't happen on the video card, so we can't recoup the MMX unit
for audio processing.

SSE was a little better.  It had larger registers.  SSE2 has single precision
floats, to my recall.

> It is interesting to note that non-MMX P/166 CPUs sell for more than MMX
> P/166 CPUs - but this is due to the voltage requirements of the CPUs I
> suspect, the MMX had special voltage requirements, and the non-MMX CPUs can
> go in lots of old systems...

P200 classics are worth even more.  I was trying to buy one about a year ago
to attempt to upgrade my sisters P90.


-- 
Joshua D. Boyd