Mark said:
Dear All, re- the Memory speed rating ..... Is it " the
higher the better " ?
I am using the Asus P4S533E Mobo and would like
to ask if I should fit it with an
Apacer 512MB DDR RAM 400Mhz PC3200 or a
333Mhz PC2700 memory module for better (faster)
performance?
The price difference between the two Apacer cards
appears to be minimal.
Thanks
The relationship isn't quite as simple as that, but your rule
is good enough in this case. Sometimes, a cycle or two of
access delay can be removed, when the CPU clock and the memory
clock are the same. When they are run at different frequencies
(asynchronous), then the logic adds resync delays. That drops
the performance, and to get the performance back, the clock speed
has to be raise a bit more to compensate. So, the relation isn't
a simple one. Even the performance curve is not smooth - there
are "bumps" in the curve, caused by the quantization of clock
ticks. But, glossing over the details, more is better.
Your board has official support for DDR333 and some people
run faster than that. If running at DDR400, you might only
expect one double sided DIMM to work at that speed. Place it
in the slot furthest from the processor. Use Google to find what
ratios are available, as that isn't documented in detail in the
manual. The CPU clock, the CPU:Mem ratio, determine the speed
of the memory. Not all available options work well, so before
booting Windows with a new set of conditions, use memtest86
from memtest.org to test the memory. Do not boot into
Windows until memtest can do some passes without error.
Memtest86 is a floppy based test program, and it doesn't need
an OS to work (it is self booting).
At DDR400 rates, sometimes the RAM needs a little extra voltage
to work well. PC2700 or lower ram is usually rated for 2.5V.
PC3200 and higher needs a minimum of 2.6V to work well at DDR400.
Overclocker memory sometimes needs a bit more (like the Mushkin
BH-6, which needs closer to 2.8V to perform well). As at least
some memory chips have internal voltage regulation for parts
of the memory, raising the voltage a lot, results in the memory
running hotter, and hotter memory runs slower. So, like everything,
there are limits to the benefits that higher voltage can bring.
Earlier motherboards don't have controls for setting Vdimm, so
that can be another reason for a memory not to perform well.
In this case, the upper limit is likely to be the Northbridge.
HTH,
Paul
