[rescue] point of pride in SGI R10k vs. 1Ghz x86...

[James Lockwood]

On Tue, 13 Nov 2001, Dave McGuire wrote:

>   Slower memory, sure...but likely not a slower memory *subsystem*.
> PeeCees aren't known for their stellar memory subsystem designs.  I
> don't have hard numbers, but I'd sure be interested if anyone does.
> James L. perhaps?

This will probably earn me some flak, but in my opinion the memory
subsystem is the weakest point of the design of the Indigo2, and the
biggest improvement that is noted in the Octane.

The memory bus carries 128 bits of data clocked at FPM RAM rates.
Accesses to main RAM are lucky to reach 100MB/s sustained, and more
frequently top off around 75MB/s.  lmbench numbers bear this out.  The
larger caches in the R10k's help as much as they do because the underlying
memory system is overstressed especially in the face of heavy
communication with the graphics rendering engines.

Even a low end Onyx will easily see twice the memory bandwidth of an I2.
An Octane or Onyx2 is higher yet.

Don't get me wrong, the I2 is my favorite SGI "desktop" in the affordable
range.  Just be aware that you're more likely to run up against a memory
bottleneck than anything else.

-James