What do you guys thing about the P4

Richard Walsh rbw at networkcs.com
Fri Apr 13 12:16:41 EDT 2001


All,

I believe the arithmetic behind the 3.2 Gbyte/sec peak
memory bandwidth in P4 system using PC800 RDRAM, and 
Intel's 850 (Tehama) chip set is as follows:

      RDRAM memory speed        =   400 MHz
      RDRAM channel width       =    x2 bytes
      RDRAM "pumps" per cycle   =    x2 
      RDRAM channels on 850     =    x2
      ---------------------------------------
      Total On Board Bandwith   =  3200 MBytes/sec

      P4 system bus speed       =   400 MHz
      P4 system bus width       =     8 bytes
      ---------------------------------------
      Total On Chip Bandwith    =  3200 MBytes/sec

(a single channel SDRAM system is  8*133=1.06 GBytes/sec)

So P4/850 motherboards with PC800 RDRAM are well balanced.
Problems with large linear systems, and cache and memory
resonant reference patterns will keep the processor 
relatively busy and hide the RDRAM latency penalty
which is about 2x that of SDRAM (the P4's faster clock 
also helps to reduce this penalty). 

I would expect G98 jobs run INCORE or DIRECTly with a 
large memory setting to show excellent performance 
especially with a compiler that can use the SSE side
of the microprocessor.

rbw

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