[rescue] Enterpise E4K questions...

[Skeezics Boondoggle]

On Wed, 16 Feb 2005, Phil Stracchino wrote:

> Gutschner, Marc wrote:
> > It currently has 4 USII at 250MHz and runs Solaris 9 quite nice. Since I
> > would like to use this machine as a test-bed for some J2EE
> > experiments, I was wondering if it would give me any benefit if I
> > spread out the available CPUs and RAM across 4 CPU boards for a little
> > more bandwidth?
> 
> Not really, no.  Other than taking up slots you could be using for I/O 
> boards.  Those CPU boards are designed to fully support two CPUs and 
> their associated RAM each; you really gain nothing by spreading out the 
> same CPUs and RAM one per board.

The US-II Enterprise machines are architecturally more like the
sun4d/XDbus machines - you don't have the memory locality issues that the
newer SunFires have, so there's a constant latency between any CPU and any
memory bank, regardless of their physical configuration.

However, you *do* want to populate the memory banks in the sequence Sun 
recommends in order to get the best interleaving possible.  Generally you 
fill up the CPU slot 0's first, and the memory bank 0's first, but the 
rules are laid out in the Ultra Enterprise Systems Manual:

http://www.sun.com/products-n-solutions/hardware/docs/pdf/802-3845-11.pdf

Chapter 3 (around page 70) has the interleave rules.  Sadly, though, you 
have to trade off the performance advantage of interleaving if you want to 
use the hot-plug features... but for goofing around at home, that's 
probably not an issue. :-)

-- Chris