Memory Not Completely Recognized

I have a KT3 Ultra MS-6380E motherboard. I was using two 512 MB
PC2100 memory sticks - no problem. I recently obtained a 1 GB PC2700
stick and have inserted it along with the other two. My BIOS
(American Megatrends version 5.7) is only reading 512 MB from the 1 GB
stick. A program I have (System Info for Windows) does recognize the
stick as a 1 GB, though.

How can the BIOS only read 512 MB when the software program reads 1
GB?

Any suggestions as to how to proceed? Thanks for any advice.

 

OK. I looked up the board, and it is a KT333 chipset.

KT333/VT8233A
http://download2.msi.com/files/downloads/mnu_exe/E6380Ev1.0.zip

I can find an experience here, in German. Using babelfish.altavista.com ,
I can translate the article. It talks about high density RAM. The OP
in this thread, installs 2x1GB of RAM, and only half of it is detected.

http://www.planet3dnow.de/vbulletin/showthread.php?t=329748

In the picture of the RAM used in that (failing) case, the RAM
is Samsung K4H510438E-TCCC. The participants in that thread mention
that the second "4" in the part number, is the chip width of 4 bits.
So the memory chip in the picture, is a 128Mx4, which is a high
density chip. High density sticks are sold on Ebay, and are not
always fully compatible or work well.

http://www.abload.de/img/module4hz.jpg

(need Flash to view table of information)
http://www.samsung.com/global/business/semiconductor/productList.do?fmly_id=115 (see K4H510438E)

Reputable manufacturers make low density sticks at the 1GB point.
But Ebay sellers don't mind selling high density RAM. They charge
less money, but the difference is in the results.

High density = (16) 128Mx4 chips
Low density = (16) 64Mx8 chips <--- the good stuff

There is nothing I can find in the documentation, to indicate the
level of support for that RAM by KT333 chipset. The problem is,
the "128M" of address space, requires a certain number of row/column
address bits on the Northbridge memory controller. When the controller
is short by one bit of addressing capability, the result is that half
the memory is detected.

http://www.via.com.tw/en/products/chipsets/legacy/kt333/

My Nforce2 is supposed to behave that way. If you install 1GB high
density DDR on Nforce2, only 512MB is detected. The Nforce2 is missing
one address bit, so cannot handle a dimension of "128M". It can handle
a dimension of "64M".

That article in German, seems to suggest the same thing is happening
with KT333.

I can look up your motherboard on the Kingston site.

http://www.ec.kingston.com/ecom/configurator_new/modelsinfo.asp?SysID=11664

They have datasheets for some of their memory products. If you examine
the module design here, you can see it uses 64Mx8 chips, so this one
is low density. As long as the motherboard manual claims support for
1GB modules, and you pick a low density one, it should be fully detected.
A high density one, may only be half-detected.

http://www.valueram.com/datasheets/KVR333X64C25_1G.pdf

"The components on this module include sixteen 64M x 8-bit"

The BIOS does two checks for memory size. It consults the tiny SPD
chip on the DIMM, for stated details about the DIMM. There, it learns
the DIMM is 1GB in size. But the BIOS also does a test which it used
to use, before SPD was invented. In older times, the BIOS does
"test writes" and figures out how big the module is, by the ability
of the module to retain data. If a "test write" cannot be read back,
then the BIOS knows there is no memory there. Due to the missing
address bit, the BIOS discovers the module functionally can only
hold 512MB, and when the test is completed, it sets up the
address decoder, based on the newly discovered "bad news".

Any Windows utility that just reads the SPD, will think the module
is 1GB in size. But the BIOS sees things differently. The job of
the BIOS, is to set up your motherboard, so it does not crash.
To hand the OS, some non-existent memory, would be a failure
of its responsibilities.

HTH,
Paul