Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <MPG.1bed0092414e181e989769@news-server.nyc.rr.com>, Louise
<none@nospam.com> wrote:
> I presently have 2 dimms of Kingston 512 installed with the following
> specs:
> Kingston Technology Kingston 512MB 400MHz DDR Non-ECC CL3 (3-3-3) DIMM
>
> I see Newegg has Crucial dimms with these specs:
> Manufacturer: Crucial
> Speed: DDR400(PC3200)
> Type: 184-Pin DDR SDRAM
> Error Checking: Non-ECC
> Registered/Unbuffered: Unbuffered
> Cas Latency: 2
> Support Voltage: 2.8V
> Organization: 64M x 64 -Bit
> Warranty: Lifetime
>
> Can I mix these two (two dimms of each). Would the shorter latency of
> the Crucial ram have a positive effect or would it be better to stick
> with more of the Kingston that I already have?
>
> TIA
>
> Louise
The BIOS will find the slowest memory, and run all memory at the
same slow speed. The Auto setting should result in you running
at CAS3, when mixing the Ballistix with the Kingston CAS3.
I've run four double sided sticks at two different timing settings.
When run at 2-2-2-6 timing, 3DMark2001 was 17793. When run at
3-3-3-8 timing, 3DMark2001 was 17322. This was at stock DDR400
rates. I believe I got a report of "PAT enabled" at 2-2-2-6.
So, if you invest in four new CAS2 sticks, you can see how much
of a difference that would make to performance. Buying two CAS3
sticks to match the two CAS3 you currently own, would be a lot
cheaper. There is nothing wrong with buying the Ballistix, as
you can experiment with them alone at CAS2, before running your
final configuration of four sticks at CAS3.
You will find advice posted on private forums, not to mix different
kinds of RAM. Some of this is FUD (fear, uncertainty, doubt)
spread by premium ram supplies. Some of it has a basis in fact,
but only if you are an overclocker. If overclocking, it pays
to have RAM with matching voltage characteristics. The Ballistix,
for example, has a max voltage of 2.8V, and doesn't really do
well with additional voltage. I've read at least one report of
someone who managed to burn up some Ballistix overnight, by using
more than 2.8V. If you were to mix the Ballistix with some Winbond
BH-5, that likes voltages of 3.1V or higher, you can see that
a product like that would not be a good choice for pairing with
some Ballistix (because you couldn't feed the Winbond the voltage
it needs, without damaging the Ballistix).
If you are planning on running the ram at nominal conditions,
unless there is some wildly divergent electrical characteristics
to the two kinds of RAM, I would expect they will work together.
(It is the same story as any RAM - you won't know for sure until
you try it.) Any voltage setting between 2.6 and 2.8V should get
the job done, and the less voltage used, the cooler the RAM will
run. I recommend a couple of passes with memtest86
(memtest.org), followed by an overnight run with one or more
copies of prime95 (mersenne.org). Don't accept the RAM unless
it runs clean. (BTW - The datasheet for the Ballistix says the
timing guaranteed by Crucial is 2-3-2-6, but people don't seem
to have a problem getting 2-2-2-6.)
As for the Vdimm setting, some Asus motherboards are not
completely honest about their voltage adjustment capabilities.
The BIOS may show you three or four possible values to select,
but if you dig out a multimeter and measure the circuit doing the
regulating, you might find there are only two working voltage
values. (I forgot to verify this when I was experimenting with
the P4C800-E - I think I did note that the BIOS value didn't
match the Vdimm, when I measured it once on the motherboard, but
didn't waste any time measuring all the values, because really,
none of the voltages applied are going to hurt anything anyway.)
The reason for this, is at least some of the regulation circuits
on the motherboard, are based on an op amp and MOSFET, and such
a circuit lacks a programmable voltage feature like a real
switching regulator provides. You can add extra resistors to the
summing junction, and make such a feature, but that would
probably be considered overkill by the motherboard designer.
Such a feature might be hard to calibrate, if you try to
add too many programmable values.
Have fun,
Paul
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