Thanks for the Memories

Charles Curley charlescurley at
Sun Nov 29 16:14:53 MST 2009

I've had an Asus M2A-VM HDMI motherboard for two years. It has done
just fine with two KVR667D2N5/1G DIMMS, for a total of two GB. I
recently decided I'd blow that out to four GB, so I ordered a
I.e.: two 1 GB DIMMs

I am getting some curious results.

The two pairs of DIMMS each test fine separately at DDR 667. I've let
each pair go for at least one full pass of memtest86+ version 2.11.

The two pair together cause the system to lock up under memtest86+,
sometimes as early as two seconds into the test. I can get a sucessful
pass on all four by reducing the bus to DDR 533. I've left an Ubuntu
9.10 live CD running overnight with all four DIMMs at DDR 667 with no
problem. I currently have Ubuntu 9.10 running, but at DDR 533.

However, when I use the BIOS to set for DDR 533, memtest86+ reports
that it is seeing DDR 550, at 275MHz. When I set the BIOS for DDR 667
(or set it to auto), memtest86+ reports 366 MHz, DDR 733. I am not
overclocking this thing, as far as I know.

Also, I get different reports of available memory. The BIOS reports
4096 MB, of which it says 3455 MB are usable. The system uses 128 MB
of that for the video RAM. finnix-92.1 64 bit says it has 3335
MB. finnix-92.1 32 bit reports 2906 MB, and Ubuntu 9.10 32 bit sees
2896 MB.

Memtest86+ tests in three chunks of memory: 144K to 2048 MB, 2048 MB
to 2943 MB, and 4096 MB to 4608 MB. The first two are contiguous, the
third is not. Ignoring the 144K, that adds up to the 3455 MB the BOIS
reports as usable.

The motherboard manual says,

"The motherboard can support 8 GB physical memory on the operating
system listed below. You may install a maximum of 2 GB DIMMs on each
                Windows® XP Professional x64 Edition
                Windows® Vista x64 Edition"

That would require four 2GB DIMMs. I would think four 1GB DIMMs would
also work just fine.


* Where is the rest of my 4 GB? I paid good money for those 641MB!

* Why the gap between the memory chunks? Not that it matters, Linux
  seems able to use them anyway.

* I suspect I have a bug in the firmware code that sets up the memory
  speed. Other than a firmware upgrade, is there anything I can do
  about it?

Any other thoughts?



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