[RC5] Performance on P-IV

Richard Menedetter ricsi at bigfoot.com
Fri May 11 15:49:08 EDT 2001


10 May 2001, Stephen Garrison <garrison at ChE.UDel.Edu> wrote:

 SG> If I remember correctly, the P-IV is entirely hardwired to do 64 bit
 SG> instructions only.

The Pentium 4 is still a IA32 processor. (like the Pentium III)
You probably mean merced/itanium whatever Intel calls its IA64 Processor

 SG> Any P-III or earlier used 32 bit instructions.
so does the P4

The problem is, that AMD had a *MUCH* superior processor, so Intel had to
do something.
They released their half ready P4 processor prematurely.

The original design was extremely cut down. (no 3rd level cache, only 1 FPU
....) and optimization logic was cut out.

This is the reason why 'normal' not optimized code runs sooooooo slow.

With the AMD Athlon non optimized normal code runs fast, and optimized code
runs very fast.
With iP4 non optimized code is a catastrophe and optimized code runs fast.

Release was simply a marketing decision, and Intel decided to make
processors with high MHz.

They hoped that people will buy them, because higher MHz numbers sound

 SG> Stephen Garrison

CU, Ricsi

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