I used to have 64 MB of memory in my computer in the form of four 16 MB 72 pin SIMMs. I decided to upgrade to 128 MB, so I bought four 32 MB 60 ns 72 pin EDO SIMMs. Problem is, when I installed them, the computer still only detected 64 MB of memory! I took the computer to a shop, and they verified the memory was 32 MB chips and that it was working. They took out 2 SIMMs and the computer only detected 32 MB, so for some reason, the computer is only detecting half the memory on each SIMM. I read my motherboard manual and it says it supports this type of memory. One more thing: even though this is EDO RAM, the BIOS does not detect it as EDO. What can I do to make the computer use all the memory?
Some older motherboards have jumpers for determining what type of memory to use. Might be worth a look.
Also supporting EDO SIMMS and max mem config are two different things. What is the maximum amount of memory the board will support?. What is the max PAIRED SIMM size the board will support? (ie it might support 4 16 megs SIMMS but only support 2 32 megs simms (not 4 )in total) There should be a memory table in the back of your manual.
My motherboard manual lists no jumpers for memory. It says it can support four 32 MB SIMMS.
You may have “high density” SIMMs. I’ve had this problem on a couple of systems where only half the memory was recognised. The system could not recognise the higher density SIMMs. I called the memory store, described the problem (“Your SIMMs are half-broken”) and fortunately the tech guy recognized the problem and sent me the low density versions. They worked fine.
As I recalled, the machines were Dells, probably P166 or thereabout (but I may be mis-remembering). Here’s a little more about it: