pc133 256mb only reads as 128mb, why?

I have an old pIII machine that takes pc133 cl3 168 pin memory in three slots for a total of 768mb. I found a newer pc133 256mb stick but it only reads as 128mb in the machine, even if it is the only stick in the machine.

What can cause a 256mb stick to be seen as 128mb? Is there anyway to fix this?

Try a tool like cpuz, and see what information is stored in the spd chip

I may be mistaken, but...

I believe some older chipsets have problems with high-density modules. If all of the chips are on one side, you likely have a high-density module. You only option is to try and find a low density 256mb stick, or perhaps try a 512mb high density. I had a P1 that only accepted 2x 128mb, but it ran great with 1x 128mb LD and 1x 256mb HD stick - saw them as 2x 128mb.

Yuriman said:

I may be mistaken, but...

I believe some older chipsets have problems with high-density modules. If all of the chips are on one side, you likely have a high-density module. You only option is to try and find a low density 256mb stick, or perhaps try a 512mb high density. I had a P1 that only accepted 2x 128mb, but it ran great with 1x 128mb LD and 1x 256mb HD stick - saw them as 2x 128mb.

Click to expand...

On the other hand, some older motherboards have problems reading various configurations of single or double sided sticks, ie if chips are on both sides it may give problems.

So tell us all, are the original 128's double or single sided, and the new 256?

Some mainboards can handle doublesided in some slots only, tried to move to another slot? I had a mainboard for K6 that would accept only singlesided in one slot. Maybe not so good example because it had something to do with that board having both SD and EDO slots, the SD slot next to the EDO slots was single sided only.

th3 said:

Some mainboards can handle doublesided in some slots only, tried to move to another slot? I had a mainboard for K6 that would accept only singlesided in one slot. Maybe not so good example because it had something to do with that board having both SD and EDO slots, the SD slot next to the EDO slots was single sided only.

Click to expand...

It does have both SD and EDO, but I didn't know there might be specific slots. The original modules are double sided DIMMS(?) and the new one has chips only on one side (high density(?)). I have a 128 single sided module as well and it is recognized as 128 but something isn't right because installing it slows the computer down to a crawl as if there are memory errors or perhaps multiple miss reads.

I will try changing slots to see if that helps. I have also read that slowing the memory down can allow all the memory to be seen. But my mobo only has 50 and 60ms timings and I believe 133 CL3 memory needs 65ms for refresh so I might be out of luck on that score.

Any body know what "passive restore" does to memory?

This is a P6BX-A+ rev 1.1 board with an award bios v1.5b which I believe allows the use of a pentium III CPU. Any body know where you can get a manual. The origion manufacturer site has the wrong manual listed when you go to download it...naturally!