February 22nd, 2002, 10:09 AM #1
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- Oct 2001
EDO and Fast Page RAM....the difference?
What is the difference basically between edo and fast page ram? Which is older? Will they work in same motherboards? Will one sometimes substitute for the other? Where is a good site with good descriptions of these older ram types? Thanks..."Even a fool is thought to be wise if he is silent"
February 22nd, 2002, 10:49 AM #2
The bandwidth is bigger with EDO so it is faster. Fast page is older than EDO. EDO memory has to be used in pairs, FP does not need to be in pairs but some motherboards do require it that way. Some motherboards can use both EDO and FP at the same time and some can not. I have had some Intel boards that can use only EDO or FP but not both at the same time.
February 24th, 2002, 04:35 PM #3
Fast Page and EDO have to do with the timings of the memory.
While FPM usually has a latency timing of 5-3-3-3 (first access takes 5 cycles, then the next accesses take 3 cycles), EDO usually has a timing of 5-2-2-2. The initial reads have the same latency, but EDO is faster with the next few reads. I seem to recall reading something about how it returns the requested row of info and caches the next row so when you request the next word it's returned faster.
It's not a good idea to mix them, becuase the timings are different (in latency and speed, too. EDO was usually 60ns while FPM was 70ns or more). Whether you can use one or the other depends on the motherboard. I think many of the 486 motherboards wouldn't have a clue how to handle EDO, so they wouldn't use it very well.
EDO and Fast Page are both 32-bit SIMMs. The type of memory has nothing to do with how many need to be put into a system, it's the CPU that drives that. 486 CPUs only required 1 SIMM at a time to read, but Pentium CPUs need 2 SIMMs to be installed. The DIMM is a 64-bit device, so that's why it can be installed singly in a system.
More info on the types can be found at:
February 24th, 2002, 05:06 PM #4
EDO stands for Extended Data Output.
Just as Night hawk mentioned it allows some bits across the bit path to be retained for the next clock cycle which then prevets the need to reread from disk (or source) before writing to memory. This allows the CPU to access parts of memory faster.
Fast Page ram is just what it states. The contents of the bit path have to be paged and reloaded every clock cycle, no matter what the contents are.
Just think.. if the RAM knows that particular bit location in RAM is currently 0...why reload the bit when you know the next bit is going to also be 0? It just retains the info for the next clock cycle unless the bit location actually changes to 1.
February 24th, 2002, 05:25 PM #5
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