[CentOS] maximum cpus/cores in CentOS 4.1

Lamar Owen lowen at pari.edu
Fri Sep 9 16:02:23 UTC 2005

On Thursday 08 September 2005 10:49, Tony Schreiner wrote:
> What is the maximum number of AMD64 cores supported by CentOS 4?

While I know this doesn't help much in this context, and doesn't directly 
answer your question, indirectly it is relevant.

The Gigaplane/UPA architecture of the Sun Enterprise XX00 (3000-6500) allows 
up to16 connections (in the 6X00; 8 connections in the E4X00 and E5X00)).  
Each pair of CPU's has local RAM on each UPA board (crossbar switched 
interconnect) that has a port on the Gigaplane bus (2.6GB/s throughput in the 
83MHz version, 3.2GB/s at 100MHz), up to 15 CPU/memory boards plus one I/O 
board per E6500 chassis/Gigaplane, giving up to 30 CPU's and 60GB of RAM 

On this hardware, the 2.6 SPARC kernel is artificially limited to 24 
processors; there seems to be stability issue over 24 CPU's.  I'm burning in 
a 2.6.12 SPARC kernel (Corona from the Aurora project) on a 14x400 E6500 now 
(16GB of RAM).

Oddly enough, the power requirements for this beast and for an octal Opteron 
are pretty matched, about 1.5KW or a little more.  Certainly the 8x Opteron 
will be faster on many things; but under heavy multiuser load the 14-way 
SPARC does a surprisingly good job, with around three quarters the 
performance of a dual 3GHz Xeon (that outclasses the SPARC box in every way 
possible except interconnect) at a load average of 30 or so.  At a load 
average of 30, the E6500 feels more responsive than my laptop (1.7GHz Pentium 
M) at a load average of 2. 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772

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