Why are there only i686 and i586 Version of glibc and kernel?

[Bryan J. Smith]

Alan Cox wrote:  
> Likewise my own testing has always found that the Athlon really
> doesn't care much how you order instructions. If you think about it
> AMD have spent years dealing with everyone optimising for random intel
> processor of the year and adapted appropriately.

I have to agree with Alan on this.  Having assembled Athlon-based
clusters from  Athlon's introduction until a year ago, the i686 (Pentium
Pro) optimizations get you very close, like within 5%, of ideal on
Athlon32.

> Except on things like 3dnow and prefetch stuff the AMD really doesn't
> seem to care.

Plus any floating point. 

Athlon32/Athlon64/Opteron has 3 FPUs, two complex and one simple.

Pentium II to Pentium IV has 2 FPUs, of which you can only do either
one complex (while one is idle) or two simple.

While the Athlon does a lot of run-time optimization via out-of-order
execution and register renaming, the compile-time optimizations can
affect things upto 40%.

But that's more of an application thing -- maybe only a few GLibC calls
(?).

-- 
Bryan J. Smith, E.I. -- b.j.smith at ieee.org