ok i have an old system with only 16mb, and it takes 72-Pin SIMM memory up to 128mb. and right now it has a pair of 4mb EDO's, and a pair of 4mb FPM's. so i wanna get two 32mb EDO's, and two 32mb FPM's.. BUT i see that for FPM's there is Parity, and Non-Parity ones. i have no clue what that means, and which one is better? Thanks -Chad

Here is an explanetion copied form the crucial site: When choosing among ECC, parity, and non-parity memory, you need to match what is already in your system. You can tell which kind you have by looking at one of the modules currently in your system. Count the number of black chips on one module. If the number of chips can be evenly divided by three or five, you should buy ECC or parity (whichever is offered for your system). If not, you should buy non-parity. Also here is a link to the page. http://www.crucial.com/crucial/pvtcontent/memorytype.asp?model=&memtype=CHOOSE Regards - Ray

Not all motherboards support ECC (parity) RAM. It's not really needed for a home computer anyway. Get the non-parity.

Parity has an extra bit so there are 9 bits per byte instead of 8. You should be able to turn off parity checking in cmos. If parity checking is off then you can use either parity or non parity RAM as the bios will ignore the extra parity bit. If parity checking is on you'll need to use parity memory, else you'll get memory errors. Ideally parity memory would be better as it gives an extra check that data is being written to and read from RAM correctly. But non-parity became a standard with simm memory and is easier to find. RAM errors are so rare that it doesn't really matter which you use.