[RC5] Performance on P-IV

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


Hi

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.
No

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

 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.

Example:
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
'cool'.

 SG> Stephen Garrison

CU, Ricsi

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