CentOS - Sep 2005 - maximum cpus/cores in CentOS 4.1

What is the maximum number of AMD64 cores supported by CentOS 4?

The RedHat page https://www.redhat.com/software/rhel/configuration/

suggests that RHEL 4 AS supports up to 8 AMD64/EM64T logical cpus. Is  
that accurate and does it apply to CentOS 4?

I see a few vendors offering boxes with 8 (dual core) CPU sockets.  
IWILL  for one.

Thanks,

Tony Schreiner
Boston College

On Thursday 08 September 2005 10:49, Tony Schreiner
wrote:
> What is the maximum number of AMD64 cores supported by CentOS 4?
>
> The RedHat page https://www.redhat.com/software/rhel/configuration/
>
> suggests that RHEL 4 AS supports up to 8 AMD64/EM64T logical cpus. Is
> that accurate and does it apply to CentOS 4?
>
> I see a few vendors offering boxes with 8 (dual core) CPU sockets.
> IWILL  for one.
The suggestion of 8 was made mostly because there was no larger x86-64 
platform available at that time. 

Also, the main reason for the limit is scalability. With more cpus comes more 
communications overhead, more congestion on the bus, less memory bandwidth 
for each cpu and so on. How much that effects you depends on your 
application. I remember in the good old days when smp was first added to the 
kernel, people said 2cpu was the max you can have... we ran a few 4way 
systems back then very effectivly simply because our application had only a 
low volume of communications. 

Peter.

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 
max).

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
(828)862-5554
www.pari.edu