computer components & hardware

In article , "ed jurewicz"
wrote:

I just added an additional gig of ram to my computer (a8ne mother board). I
now have 4 sticks of 512 crucial filling out all memory banks; however both
windows system and the post do not report the increase. They show only the
initial 1g.

Is there a way of tracing this problem.?

First of all, you will need to dump the contents of the SPD on
each DIMM. You can try Everest Home Edition (lavalys.com) or
find some other tool for the job.

There have been scattered reports in the past, with problems
with the matching of DIMMs on Asus Athlon64 S939 boards. These
would be BIOS problems presumably, as the BIOS parses the
contents of the DIMMs, to figure out what settings to use
in the processor's memory controller.

One poster had a problem, where the revision number of the
module or PCB didn't match, between a pair of DIMMs,
and the BIOS decided he wasn't using matched memory. Of course,
that is plainly badly written BIOS code, as the BIOS should only
be comparing rows, columns, banks, ranks, memory timing and so
on.

Now, if you have a revision E processor, like a Venice, a mismatch
between your four DIMMs, would put you in virtual single channel
mode. If all the DIMMs were different, they could still be used
as 4x512, but only one DIMM would be used at a time.

If you have an older processor, a pre-revE, then once two matching
DIMMs are detected (like the first two you owned), the BIOS
knows it is going to run dual channel mode based on those two.
The BIOS then examines the second two DIMMs, and if they don't
match, one option for the BIOS is to ignore them. Based on the
symptoms, I would say that is your current situation. (I don't
think the BIOS code is clever enough to only try slot B1 and B2
in single channel mode in that case. The code is pretty dumb.)

Your options would be to upgrade the BIOS (if you haven't already)
and see if that helps. If checking the contents of the SPD, shows
that you have two perfectly matched pairs (but one pair is not the
same as the other pair), then you really cannot blame the memory
manufacturer. I have read of one case, where someone using 4x256
could only get half the memory to work, even though the pairs
were matched (but not all four sticks matched).

If reading a dump of the SPD on the DIMMs, there are some fields
that don't have to match. There is the manufacturing date and
the product serial number may differ between sticks. For example,
the BIOS really shouldn't be looking at stuff above byte 63, but
it might...

(JEDEC DDR SPD spec)
http://web.archive.org/web/200304170..._02_04R11A.PDF

HTH,
Paul