So what's wrong with my RAM?

I recently dismantled my clapped out P100 and put the harddrive in my only slightly older 486 to keep the older machine going. It works just fine but I wanted to add the RAM from the P100 as well. It fitted easily and seemed to be of the same type but then I wouldn’t be too sure. The machine however still says that it has only the original 16mB of RAM and not the 32mB it should have with the new RAM added. Is there anything else I need to do to let the machine know I’ve added this memory? I thought it might do this automatically.


The BIOSes of PCs are only programmed to handle memory of certain sizes and configurations. In all prob., your older computer is just incable of recognizing that particular size or configuration of memory. Since it’s a 486, you probably can’t flash the BIOS to a newer version. But check at []Wim’s BIOS page.

(The number of times people in the computer business fail to anticipate even small future developments is amazing and then some.)

On a lot of older computers, you need to go into the BIOS setup (pressing F1 or whatever the magical key sequence is for your computer, read the screen when it boots). Most times you don’t need to do anything, just verify that it correctly reads the new memory amount, then press save and exit. On some systems you may need to force it to check for new memory, but on 486’s that was rare.

What type SIMMS do you have in there? Two 16M ones should work fine (it’s unlikely anything under 64M would have been considered too large, even in the 486 era)…

I second the BIOS check notion. It should be working w/o that, but that’s the only thing I can think of.

You added EDO RAM (the standard RAM for Pentium systems) and the 486 requires FPM RAM. They look identical, EDO just doesn’t work in FPM systems. FPM does work in EDO systems.