BX Master Memory Question

[Desciple]

Hello all,

After visiting Microstar's site and downloading the (PDF) manual, I am confused by the memory requirements and limits. In one place (page 1-2, under "Mainboard Features" heading) it states support for eight memory banks using three 168-pin unbuffered DIMM. Supports a max memory size of 384MB (8Mx8) or 768MB (16Mx4) registered DIMM only. Supports ECC (1-bit). Supports 3.3v SDRAM DIMM.

Then on page 2-6, under the "Memory Installation" heading, it states "The mainboard supports a maximum memory size of 512MB (8Mx8) or 1G (16Mx4) registered DIMM for SDRAM: It provides four 168-pin unbuffered DIMMs (Double In-Line Memory Module) sockets. It supports 8MB to 256 Mbytes memory module."

The board has four DIMM slots. I'm currently using 2 128MB PC-100's. Figuring that installing additional ram at PC-133 would be OK, it'd just run at 100, I tried installing one additional 256mb (PC-133, on sale very cheap) stick and expected the memory to jump to 512 (seemed logical at the time) but during POST the memory test stops at 384. Under Win98 I have run some memory tests and these numbers confirm the 384 POST reading, so I'm pretty sure all my ram is not being used or recognized.

I know a lot of you out there have had lots of experience with these very fine motherboards, so I know someone out there can most likely tell me what I did wrong.

Any help would be appreciated.

My setup: BX Master, P-III 750, FSB@100, 256 ram (2 x 128), Geforce AGP DDR.

Thanks for your interest in my question. Please post any theories, hints, links, or experiences that you think may help.

Desciple

 

[Peter]

Intel BX has a technical limit of 128 MBytes per DIMM _side_. So if you got a single sided 256-MByte stick there, it'll be unable to use more than 128. You need double sided 256-MByte sticks made from "16x8" technology SDRAM chips, not "32x4" pseudo-double-sided nor "32x8" single sided.

 

[Jhhnn]

What Peter said, except in simpler terms- BX chipsets cannot use memory with a density greater than 16megs/chip. 256meg sticks must have 16 chips, 8 on each side....

Memory labelled as pc100 rather than pc133 is almost always right, as the makers take this factor into account...

 

[Desciple]

Thanks very much Peter and Jhhnn, you have both helped very much.

Cheers,
Desciple

 

[Peter]

Originally posted by: Jhhnn
What Peter said, except in simpler terms- BX chipsets cannot use memory with a density greater than 16megs/chip. 256meg sticks must have 16 chips, 8 on each side....

... which is not enough of a criteria. Chip density is counted in megaBITS, so that would be 128 MBit not 16 MByte please. Anyway, Intel BX cannot even run all flavors of 128-MBit SDRAM, you need to have "16x8" geometry chips. "32x4" looks the same (16 chips, 8 on each side) but does NOT work with this chipset.

 

[Desciple]

Thanks, Peter, for the additional clarifiation.

Cheers,
Desciple