Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <7bqdnc6RNdXf5k3dRVn-tw@comcast.com>, "Harry Waldvogel"
<hjwaldvogel@comspamcast.net> wrote:
> Are there any issues using 4 dimms with the P4P800 or P4C800 motherboards.
> Some boards seem to take a performance hit with more than 2 dimms.
> I plan on building a machine for editing photographs and may need more than
> 1 GB memory. I would like to start with 1GB (2x512) and be able to add more
> if needed without a performance hit, rather than buying 2GB to start.
>
> Harry
When operated at stock speed, there shouldn't be a problem. You
can run four DIMMs at DDR400, just as easily as two DIMMs. This
guide will partially explain some of the features of 875/865
Northbridge memory controllers:
ftp://download.intel.com/design/chipsets/applnots/25273001.pdf
The issue is when overclocking. There is a feature called PAT,
which Intel intended to work on the P4C800 when operated at
stock speed. You'll need to do some searches in the forums on
abxzone.com, to try and keep up with the various efforts to
establish precisely when PAT is available on P4P or P4C boards.
A useful search term is "ctiaw", as that is the name of a utility
used to check the status of PAT on a board, while in Windows.
The overclockers seek to enable "full PAT" while overclocking,
and Intel doesn't guarantee the timing under those conditions.
That isn't stopping the intrepid from trying anyway.
A second issue with overclocking, is max memory bus clock speed.
One person on abxzone, runs four DIMMs at DDR440. I'm not aware
of anyone going faster than this (but, I also haven't been searching
for this lately, either). With two DIMMs, you can overclock to
DDR500, using PC4000 DIMMs and 3-4-4-8 (relaxed) timings. This
gives nice memory benchmark numbers, as pipelining of commands and
data at rates above DDR400, tends to hide the inefficiencies of
3-4-4-8 timing.
So, for absolutely fastest memory performance, you want a P4C800
running 1:1 CPU:FSB ratio, and two PC4000 DIMMs. A P4P800 will
throw up video artifacts under these conditions. Either board
is probably fine running four DIMMs at DDR440, and a ratio like
5:4 CPU:FSB. The "artifact" thread on P4P800 (865PE) boards is
here, so you can judge the risks while overclocking the P4P800:
http://abxzone.com/forums/showthread.php?t=62275&highlight=artifact+p4p800
The problem is, if you spend money on (2) PC4000 now, then when
you buy two more later, you won't be able to run them at DDR500
any more. You can tighten the timing a bit, when the mem clock is
dropped in speed, but exactly how much, and how much you "lose"
this way, has to be established by experiment. With Photoshop,
having memory available is the most important thing, at least
compared to the delay of swapping to the scratch disk. If your
images are large enough, 2GB of slow memory is worth more to
you than 1GB of fast memory.
I think you could spend several days reading threads on performance
enhancing those motherboards. More time than I want to spend
right now
If abxzone.com encouraged shorter threads, it would
make research at lot easier. A thread with a couple thousand posts
of varying relevance in it, isn't a lot of fun to read.
Paul
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