P4C800-E Deluxe - CPU speed vs Timming vs Memory speed?

In article , NEM
wrote:

Hi,

I've spend a bit of time going through and writing down all the various
setting combinations for OC'ing the system listed below. It boils down
to CPU speed vs memory speed. Which is more important in your opinion?

For example...

CPU |FSB |CAS |MB/s
------+--------------+-------------+------
3375 |225 (DDR450) |2-3-2-6-4 |2929

...vs...

CPU |FSB |CAS |MB/s
------+--------------+-------------+------
3405 |227 (DDR454) |2.5-3-2-6-4 |2893

...I know, I know, there isn't a lot of differences, but these are
rather extreme example settings. The differences are more apparent with
lower OC'ing, something of which I plan to eventually use.

System currently runs 40c under full load using stock heat sink (lapped
and AS5 used) and Motherboard at 27c using the above settings. All
memory test were run using Test#5 repeatedly (30+ passes) in Memtest86+
v1.0.

System:
~~~~~~~
Asus P4C800-E Deluxe
Mushkin PC3500 Level II 512MBx4
P4 3.0c
Antec PLUS 1080AMG case

Thanks for reading,

Generally speaking, "clock rate is king". Whatever you lose via having
to increase the CAS setting, you can more than make up by the ability to
increase clock rate (at least until something else breaks).

So, for example, people buy PC4000 memory, because it runs at DDR500.
DDR500 is 25% more than DDR400, but the memory might have to run at
CAS 3 instead of CAS 2 . The CAS increase costs 10% of your performance
increase, leaving you with a net increase of 15%.

In your example, at the point you are forced to change from CAS2 to
CAS2.5, that is a bad point to leave the clock at. This is because
you've taken a hit on performance due to the CAS increasing, but you
haven't increased the clock enough to "pay back" what the CAS change
has cost you.

Clock speed alone should be giving you a "linear" performance ramp,
but every time CAS changes, that is a downward "stair-step". The
sum of those two functions gives you the memory bandwidth
performance curve.

Because of the fact that clock rate is king, that is why people
are happy to buy 3-4-4-8 memory for PC4000, because the higher clock
rate makes the memory timings irrelevant. (As long as you are harnessing
the extended clock rate range of course - buying PC4000 memory and
running it at DDR400 doesn't make too much sense. If a user plans on
staying at stock speed, the money would be better spent on a PC3200
low-CAS memory.)

HTH,
Paul