To: Petz who wrote (77294 ) 10/27/1999 2:10:00 AM From: Goutam Respond to
Petz,ixbt-labs.com ____________*** 1 *** DDR DRAM is a pure evolution and not a revolution as Direct RDRAM proved to be. This memory type is based on the same principles, as SDRAM does, with the only difference that it has an additional number of important features. Firstly, it utilizes a more progressive synchronization, which is absent in SDRAM. Secondly, DDR uses DLL (delay-locked loop) to receive a DataStrobe signal, which implies that the data in the output contacts are accessible. Using DataSrtobe for each 16 outputs allows the controller a more exact data access and synchronization of the data incoming from different modules located in one bank.*** 2 *** The main distinctive feature of DDR DRAM compared to SDRAM is the possibility to transfer the data at both edges of the clock frequency signal similar to Direct RDRAM. And - here you can start applauding - as a result we get an automatic doubling of the peak bandwidth compared to that of SDRAM working at the same basic frequency. *** 3 *** DDR-PC266 Direct RDRAM Looks far less impressive, actually. (According to VIA, the factual bandwidth of DDR266 and 800MHz DRDRAM makes 1.36 and 1.12GB/s correspondingly, however, we shouldn't regard this figures as objective since VIA may be pursuing interested motives;-) ) *** 4 *** DDR DRAM is based on SDRAM and hence borrowed a lot of other features from its predecessor except its speed. For example, being much faster than Direct RDRAM, DDR consumes significantly less power. DDR 200 needs almost the same power as PC100 module. Though they are of the same size, DIMM DDR has 184 contacts while DIMM SDRAM only 168. That's why unfortunately, any direct change to a new memory type turns out absolutely impossible. However, the problem seems to be solved by means of placing the slots for both: 168- and 184-contact DIMM modules. This idea is actually similar to the solution offered on the low-cost mainboards where you can see both: SIMM and DIMM slots.ixbt-labs.com *** 5 *** As for the price, again we repeat that it is likely to remain the same as that for SDRAM, because DDR manufacturing does not require any additional investments: the equipment, the tests and chip package used (TSOP) are more than enough. And as a result, unlike the situation with Direct RDRAM, DDR manufacturers are perfectly ready for mass production and all they wait for now is the mainboards.
