You may have much better luck with pc5300 ram. This newsgroup has dozens of
postings on the problems of trying to use pc6400 ram in all four dimm slots
on many mobos. I am running 3 2GB dimms in this machine now because it will
not boot with all 4 slots filled. The amount of memory is not the issue but
the number of dimms used seems to be. Research your mobo on the
manufacturer's website and especially the user forums there. And read the
threads on this newsgroup on similar problems with ram.

"Noel" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> I am putting together a new build and since PC-6400 DDR2 is sooo cheap I
> thought I might consider 8GB on an X38 board.
>
> I already have 2x2GB dimms, and was guessing if I went to 8GB it might
> be nice to have 4 identical DIMMS, which are still available (ie,
> another 2x2gb of the pair I have now).
>
> Anyone have wisdom about this? My main uses NOW are MS Flight
> Simulator, Gigastudio, and both of those benefit from at least 3GB,
> beyond that I don't know. I don't forsee video editing . . .
>
> Thanks for your replies,
>
> Noel
>
>
> --
> Noel

Based on my reading in the newsgroups, running 667 should be OK. You did
mention pc6400 but did not say you were not running it at 800.

"Noel" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> Colin Barnhorst;578269 Wrote:
>> You may have much better luck with pc5300 ram. This newsgroup has dozens
>> of
>> postings on the problems of trying to use pc6400 ram in all four dimm
>> slots
>> on many mobos.
>>
>> Hmm, wonder why the bandwidth rating of the DIMMS would have anything
>> to do with the outcome in this instance. I've already purchased PC6400
>> DIMMS so will try them and see. For what it's worth, they will be
>> running at 333mHz, not 400mHz.
>>
>> There are reports of success with Vista 64 and 4 x 2GB as well, on P35
>> chipsets.
>
>
> --
> Noel

You mean lowering the voltage or dram speed in the BIOS? Yes, that has been
discussed. There is no one fix that applies to all these situations, but
that is one that usually helps.

"Jeff Flowerday" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>
> Colin Barnhorst;578269 Wrote:
>> You may have much better luck with pc5300 ram. This newsgroup has dozens
>> of
>> postings on the problems of trying to use pc6400 ram in all four dimm
>> slots
>> on many mobos. I am running 3 2GB dimms in this machine now because it
>> will
>> not boot with all 4 slots filled. The amount of memory is not the issue
>> but
>> the number of dimms used seems to be. Research your mobo on the
>> manufacturer's website and especially the user forums there. And read
>> the
>> threads on this newsgroup on similar problems with ram.
>>
>> "Noel" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...> > >
>> > >
>> > > I am putting together a new build and since PC-6400 DDR2 is sooo
>> > cheap I
>> > > thought I might consider 8GB on an X38 board.
>> > >
>> > > I already have 2x2GB dimms, and was guessing if I went to 8GB it
>> > might
>> > > be nice to have 4 identical DIMMS, which are still available (ie,
>> > > another 2x2gb of the pair I have now).
>> > >
>> > > Anyone have wisdom about this? My main uses NOW are MS Flight
>> > > Simulator, Gigastudio, and both of those benefit from at least 3GB,
>> > > beyond that I don't know. I don't forsee video editing . . .
>> > >
>> > > Thanks for your replies,
>> > >
>> > > Noel
>> > >
>> > >
>> > > --
>> > > Noel > >
>
> Did any of these people look at bumping up the voltage a bit on the
> memory? It's common problem when using all four slots with newer faster
> memory.
>
>
> --
> Jeff Flowerday