Originally posted by: mpchen
Hi there:
I am thinking of buying more RAM for my desktop but since I have an old Motherboard
( ASUS P5VDC-MX ) , I am wondering if I can just put in these DDR2 800 module and expect them to run fine. Of course I understand I won't be running the memory at 800 but only at 667 or 533. My concern is with the memory voltage requirement as these DDR2 800 modules are spec'ed to run at 2.0+ V. If I run them at a lower speed, I assume the voltage required will be less. Do you I 'll run into problems? Thanks for your advice in advance.
Mike
So I gather that you have no control of RAM voltage settings on your Motherboard?
If that's so, the voltage it generates is probably a fixed 1.8V, though possibly
(if you're in more luck) maybe it does internally read the voltage from SPD / EPP
information in the settings EEPROM on each RAM stick and sets the voltage accordingly.
I suppose the distinction between those two situations could be relevant to you.
Also it's possible there's a trivial "volt mod" change that can be done for your motherboard
either with a software program or with a simple hardware jumper or similar change that
could raise the RAM power supply voltage. I'd google for "volt mod" and the model number
of your motherboard.
Anyway yes DDR2-800 modules will certainly WORK at DDR2-533 or DDR2-667 speeds,
and they're likely to need less voltage to do so, and/or also they're likely able to
run at faster cycle timings as you slow their clock rate.
I would guess you're probably going to be able to run them at DDR2-667 or DDR2-533
at 1.8V without errors at 5-5-5-15 or maybe even more conservatively 6-6-6-18 or
5-5-5-18 timings.
For the current prices they seem like a good investment since they'll likely work now,
and be useful in the future if you upgrade your CPU/motherboard within the next year
so you can run them at their full speed.
I can't easily test stability of these for you at 1.8V / DDR2-667, but I have a limited
bit of information. I'm running TWO of these T8UB2GC5 eWiz DIMMs (rated at 2.1V)
ALONG WITH TWO Patriot DIMMs (which are rated at 2.0V). I was ALMOST stable
at stock frequency/timings of 800 MHz and 5-5-5-15 cycle timings, but I did have
a few bursts of memtest errors as I let it run overnight at undervolted (1.8V).
So nothing could be inferred from the failure, since it could be due to my PATRIOT RAM
and not the SUPERTALENT, or it could have been due to the CPU overclock too.
But when I lowered the CPU overclock and raised the RAM voltage to 2.0V (still less than
the SUPERTALENT 2.1 specification), everything was stable over 24 hours of memtest
with no errors.
I certainly suspect at the lower frequency you could go to 1.8V. Maybe I'll run memtest
on that system at DDR2-667 and 1.8V until tomorrow evening and let you know if
it passes, though if it fails, again, it could be due to the PATRIOT 2.0V RAM, so it's
not totally conclusive.