Gene,
Thanks for the ServerWorks links. I had just about finished an exhaustive response based on a tour of the website when my browser blew up (DAMN!), so here's an abbreviated summary of what I found:
JEDEC only has a 64Mb DDR chip spec (version 0.9). There are no specs available that I could find for any DIMMs at all!
AMI2 has no information on it's own site that I could find, but provides links to the JEDEC 64Mb chip spec (see above) and something called a DDR Spec Helpbook (or something like that). The Helpbook link points to a Mosaid site, but doesn't work.
So as far as I can find, there are no DIMM specs at all on either "standards" organizations pages and a spec only for the 64Mb DDR chip (no 128Mb or 256Mb, and while maybe it's easily extensible, the issue is "consistency" across manufacturers -- how consistent will the extensions be if there's no central spec?). I'd be very interested in finding out if I've missed something.
As for the chipset and DRAM manufacturers, there are specs floating around, but all the ones I checked have disclaimers about them not being final.
Serverworks provides their own spec for Registered DIMMs (version 0.9, so not final).
Via points to JEDEC, AMI2, Micron, and IBM.
Micron has a link for version 0.9 specs for Unregistered DIMMs, but it doesn't work. The version 0.6 spec does. They also have some kind of design guides, but those are heavily asterisked as not being final. Finally, they also publish information on validation, but point out that their validation is not a functional validation -- it only tests the PCB layout.
My browser blew up as I was about to register for the IBM site, so I have no feedback.
So it appears that each vendor is publishing their own DIMM spec, though I haven't found any overlap, so maybe ServerWorks will become the de facto standard for Registered DIMMs, Micron for Unregistered DIMMs, et cetera. I couldn't find any text that indicated this, however.
In summary, I don't see a lot of "standards-driving" happening from JEDEC and AMI2, and I don't see any final specs anywhere.
Dave |
