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RAM chip lingo

Posted on 1999-07-27
Medium Priority
Last Modified: 2013-11-10
I'm shopping for more memory for my PowerMac 9500 with G3 upgrade.  Currently I have 144MB (64+64+8+8).  What is the difference between a "5v FPM 64MB DIMM" and a "5v EDO 64MB DIMM?"  I think I purchased EDO's last time.  I have them interleaved, and want to continue doing so.  Is it a compatibility issue or a performance issue between FPM and EDO?
Question by:archken
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Expert Comment

ID: 1159992
5v=5 volts
64MB=64 MegaBytes
FPM=Fast Page Mode
EDO=Extended Data Out
DIMM=Dual Inline Memory Module.

EDO is an improvement over FPM.  The major difference is that EDO needs to be refreshed less often than FPM.  This allows a longer period that the RAM is active, thereby incresing the speed, meaning more data can be transferred in an equal amount of time.

To quote from an A+ Certification text:

"Mixing EDO and FPM RAM is not a good idea.  Most systems that use EDO will run with FPM RAM, but you lose the benefit of EDO."

FPM may be cheaper, so balance price against performance.

Author Comment

ID: 1159993
Great answers.  Thanks.
Now that I know I want EDO, how do I find out for sure what type of DIMMs are already in the computer?  If my two 8MB DIMMs are FPM, I can chuck them.  Or just chuck them without question.  But those two existing 64MB DIMMs I'd probably want to keep.  Are they usually marked with a label?  Or is there a software utility that can tell me?  BTW, you deserve some points for your answer.

Accepted Solution

chewymon earned 400 total points
ID: 1159994
I am not too familiar with MACs, but on my PC during the POST on boot it gives me this message:


Check your BIOS and system information, maybe system moniter program.  However, I don't know of anyone that made 64 MB FPM RAM, so those are probably EDO.  RAM usally is not labeled.  You can get the model numbers and check the manufactures website.  There probably is a utility to tell you.  Check  You might consider changing to SDRAM if your machine supports it.  4-6 times faster than EDO.


Author Comment

ID: 1159995
SDRAM, unfortunately, does not work on my Mac.  I think they only work on the new G3 Macs.  Thanks for the helpful info.

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