A little advice/help needed
I've just installed som OCZ DDR RAM PC3200 into my PC (Abit AN8 MoBo)
after a double helping of Crucial Ballistix problems and was just
wondering what was the correct settings to apply in the BIOS/CMOS etc,
RAM timings? I had it set manual for the Ballistix, slowed down the
timings to stop the majority of BSoD's. I now have new OZC RAM
(2x512MB Matched Pair) and set it to SPD? Should I set this to Auto?
Also the Ballistix were 2.8v, so I have now set the OCZ to 2.6v,
should this also be something that is automatically detected and set?
I only ask as I want to be sure I have things set correctly to get
some confidence with it all.
Many thanks
Keith (Southend)
http://www.southendweather.net
Timing is stored in the SPD on the DIMM, but the custom voltage setting
are not, for DDR memory. (There is a non-standard way to do it for DDR2,
but if you follow JEDEC only, there isn't a way there either. Byte 8
in the SPD states the nominal voltage value to be used.)
JEDEC SPD spec for DDR memory, so you can see what is in there...
http://web.archive.org/web/20030417070529/http://www.jedec.org/download/search/4_01_02_04R11A.PDF
You only use enough voltage to get the job done. The Ballistix is not
a high voltage memory, and 2.8V could well be the max, not an invitation
to set them at 2.8V the instant you get them.
On some DRAM chips at least, the chip has a voltage regulator inside.
Which means excess voltage is simply dumped as heat. Where the extra
voltage might be helping, is on the I/O pads.
When you get new RAM, set it to Auto in the BIOS, and then you can review
the settings it used later, with a Windows utility. Some enthusiast
RAM, rated to run above PC3200, will only have PC3200 timings in the SPD,
to allow the motherboard to run the first time the memory is used. That
means, you may need to set up the memory manually, to get to the value
stated in the product advertising.
On an S939 board, the memory controller is inside the processor. With a
single pair of RAM, you should be able to run DDR400 rate, with Command
Rate set to 1T (one command per clock cycle, on the address bus). When
using two pairs of sticks, many BIOS will drop this, and use DDR333 rate
or perhaps drop the Command Rate to 2T (one command for every two clock
cycles). The extended Command Rate, allows time for the command to settle
on a heavily loaded address bus. (The BIOS design follows the instructions
provided by AMD, for use with their processors. But that doesn't stop the
end user from being more aggressive. Finding errors is what tells you
that you've gone too far.)
Apply only enough voltage for stability. You can start at 2.6 to 2.7V, and
use memtest86+ to check for errors. If there were only a couple errors
in a few complete passes, then maybe a voltage increase might make a
difference. But it could just as well be, that the RAM is not really
as speedy as the label claims. At least with the Ballistix, there is
half a chance they will use good test techniques. (Since the DIMM could
have been made in a Micron plant.) I have four sticks of Ballistix, running
dual channel in two computers, and have no complaints about them.
Paul
