sylvester,
Just to clear up the DDR vs. RDRAM validation issue (since Carl is apparently not going to do it):
Rambus maintains very tight control over the validation process for RDRAM-related products. Here's the text from their RIMM validation page...
The RIMM module validation program enables Rambus system designers to quickly check the compliance of a module. During validation, RIMM and Continuity RIMM Modules undergo precision characterization of critical electrical parameters, such as impedance, propagation delay, attenuation, and forward & backwards cross-talk, as outlined in the RIMM Module Specification.
Third party validation laboratories conduct the RIMM module validation. Memory module manufacturers should send 2 samples of pre-tested RIMM modules directly to the validation labs. Each specific module design (PCB/RDRAM combination) must be verified. Rambus RIMM Modules which meet all specification parameters are validated for a period of 6 months or until a design, PCB or RDRAM supplier is changed. A current list of validated RIMM Modules are posted weekly at the site below:
This tight control ensures that all components work together interchangeably and is a strong benefit of having a central organization controlling the specification (whether it be Rambus or Intel or whoever). As you can see, validation is only for 6 months and then the RIMMs have to be retested if you wish to continue selling them. The validation labs will ensure that everything works together.
Since RDRAM systems began shipping, we haven't had a single report of problems with interoperability of RDRAM components (820/840s with RIMMs).
As for DDR, I don't know if JEDEC or AMI2 is planning on setting up a central clearinghouse to verify components, but Carl says each vendor will be responsible for their own testing, so we'll go with that.
What does that mean? It means that some motherboard/system manufacturers will perform tests with all available DDR DIMMs at the time they ship the mobo. But will they keep up with new DDR DIMMs? If not, customers may have compatibility problems when they add memory to their system later. Some of the lesser manufacturers may not even test with all the DDR DIMMs on the market -- they may just test with some subset from the leading manufacturers DIMMs. In which case, if you buy a mobo, it may not ever work with the first DDR DIMMs you put in it.
With no central control over testing, there will almost assuredly be incompatibility problems. This has the "PC100" smell all over it unless a central organization is put in place to test products. And even then, without central licensing, such as Rambus enforces, who says the manufacturers have to submit your products for testing even then?
Good luck to the customers who buy DDR systems.
Dave
p.s. I'm pretty sure you know this -- I'm summarizing primarily for those who don't. |
