What is EDO Memory?
Extended Data-Out (EDO) is a DRAM chip technology which improves memory performance
10 to 15% over equivalent Fast Page Mode devices.
Computer systems must be designed to take advantage of this performance increase
Intel's Triton Chip set, used in Pentium-class computers, are designed to do
just that. EDO memory may be installed into most other computer systems but
they will function and perform
as a Fast Page Mode memory module.
How does EDO Work?
DRAM's are designed as a matrix of bits. Each bit is accessed by a row and column
address. A memory controller inside a computer system provides those addresses
to access the data that each bit contains.
A 60ns DRAM will provide that data to the memory controller within 60ns. But
there are certain time constraints for the memory controller to set-up the addresses,
receive the data, and prepare for the next cycle. An entire memory cycle can
range from 85 to 120ns.
Fast Page Mode can decrease cycle times by allowing the memory controller to
access other data bits which are in the same row address. This saves time by
not having to set up the next row address instruction. Data accessed in the
same row is referred to as a "page".
Extended Data-Out (EDO) can improve cycle times even further by allowing the
memory controller to begin a new column address instruction while it is reading
data at the current address. Unlike FPM, the data output drivers are not turned
off when the memory controller removes the column address to begin the next
cycle. This saves approximately 10ns per cycle.
Do EDO SIMMS Look Different?
EDO SIMMS look very much like a standard SIMM.
Only the type of DRAM chip used on the module is different.