Re: Looking for the cause of poor I/O performance

quoted

System A:
CPUs	2 X 500 MHz
RAM	4 X 128 Meg SDRAM
Bus	100 MHz
Timing buffer-cache reads:   128 MB in  0.87 seconds =147.13 MB/sec

System B:
CPUs	2 X 1000 MHz
RAM	4 X 256 Meg Registered SDRAM
Bus	100 MHz
Timing buffer-cache reads:   524 MB in  2.00 seconds =262.00 MB/sec

Why is system B almost twice as fast?

the buffer-cache is measuring systemcall overhead as well as speed of 
pagecache-to-user-buffer copying.  both those are certainly influenced
by the CPU speed - even by things like mmx.

quoted

Is registered RAM faster?

no, it's inherently slower (mostly latency, but since bursts are short,
also in bandwidth.)

Memory interleaving, perhaps? Registered ram has higher latency. It's possible 
that the machine is made to do memory interleaving with ECC ram to boost 
performance.. 

sdram means that interleaving is basically irrelevant.  interleaving was
important when a single bank of ram couldn't sustain one transaction per
cycle (EDO, FPM, etc).