EDO stands for Extended Data Output. It is the newest DRAM chip technology
in a line of innovations which include nibble mode, write per bit, and
fast page mode.
EDO is one step better than fast page mode; for a given speed of chip (i.e. 70ns, 60ns) EDO chips allow the CPU to access memory 10 to 15% faster than fast page mode chips. However, a computer system must be designedto make use of the extra efficiency EDO offers. Pentium-class computers using Intel's Triton chip set are designed to use EDO memory.
If you put an EDO memory module in a machine that doesn't recognize EDO, the system will work, but there will be no performance increase.
A DRAM chip is designed as a matrix of bits; each bit has a row address
and a column address. The memory controller must tell the chip the row
address and then the column address in order to retrieve the data that
each bit holds.
A 70ns chip must produce a bit of data within 70ns. In addition to the 70ns required to retrieve the data from the chip, there is extra time involved in getting the data to the CPU and setting up to give the next instruction.
An entire memory access cycle, from the time the memory controller gives an address to the memory chip to the time the memory controller is ready to give the next address to the memory chip, can range from 85 to 125ns.
Each improvement in chip technology makes the process a little more efficient.For example, fast page mode technology was an innovation that made it fasterto access data in the same row. If a bit was in the same row as the previous bit, the memory controller would not have to repeat the row address instruction; it would only have to give the next column address. Thus, the efficiency and speed of retrieving data was improved for all data on the same 'page'.
EDO memory holds the newest innovation in memory retrieval. It enables the memory controller to save even more time by cutting out a 10ns wait period that is normally required before issuing the next column address. The processor receives the data faster, and therefore, the performance of the computer increases by 10 to 15%.
An EDO memory module does not look much different from a standard non-parity
memory module. The only difference is the type of chip on the PC board.
Kingston Technology currently offers EDO memory in the general memory
product line for developers who already have boards with the Triton chip
As computers are released that can make use of EDO memory, Kingston will release EDO memory according to the specifications of those systems.
EDO memory chips will be used on SIMMs, DIMMs, proprietary modules, and video memory.