Re: Sun E4500 Memory Interleave Oddity

From: Scott Howard (scott_at_hunterlink.net.au)
Date: 08/27/04 

Date: 27 Aug 2004 14:37:15 GMT

Keg <rhugga@yahoo.com> wrote:
> I noticed this in the output of prtdiag. We just had a DIMM replaced
> and now I'm not sure if this was like this before or after the
> maintenance. The is an E4500 with 10 cpu's/10gb memory.
[...]
> If you notice, the interleave on Bank 1 of boards 6&7 is different. Do
> I have a problem here?

Banks of memory can only interleave in a power-of-2 ratio.
ie, 2 banks, 4 banks, 8 banks, 16 banks, etc.

In your case with 10 banks of same-sized memory, the most optimal
interleaving is one 8-way and one 2-way interleave, which is exactly
what you're seeing.

This will give you (very slightly) lower performance out of the 2-way
banks than the 8-way banks, but not enough to worry about - especially
as there's nothing you can do to avoid it.

  Scott.