What are FB-DIMMs?

[AmberClad]

I think the question title is pretty self-explanatory. I read the Wikipedia article but still don't really have a good sense of what the purpose of FB-DIMMs are. Are they like ECC registered RAM and only used in servers, where errors are more of a concern than with a regular desktop?

(yes, yet another IDF-inspired question)

 

[Blain]

You don't need to worry about registered/buffered DIMMs on regular desktop MBs.

 

[AmberClad]

Originally posted by: Blain
You don't need to worry about registered/buffered DIMMs on regular desktop MBs.

Unless that regular desktop motherboard happens to be codenamed Skulltrail apparently. (no, I'm not considering getting one, just curious about the RAM)

 

[Blain]

Originally posted by: AmberClad

Originally posted by: Blain
You don't need to worry about registered/buffered DIMMs on regular desktop MBs.

Unless that regular desktop motherboard happens to be codenamed Skulltrail apparently.

That's not a "regular desktop MB" at all.

 

[AmberClad]

Originally posted by: Blain
That's not a "regular desktop MB" at all.

Fine, fine, fine.

"Unless that desktop motherboard happens to be codenamed Skulltrail apparently."

There, happy ? But, I still want to know what the hell FB-DIMMs are and what makes them so special.

 

[Blain]

Fully Buffered

 

[AmberClad]

Originally posted by: Blain
Fully Buffered

Oy vey :|. The same Wiki article that I said in my original post I had already read.

*sigh* Sorry, it's not your fault. I just can't find seem to find a good article that explains it in terms that a layman or a enthusiast, not a hardware engineer, would understand.

 

[Twsmit]

You can think of FBD as a sort of modern Rambus RDRAM implementation for servers and high end workstations such as the mac Pro. Basically the ram modules have a buffer chip in them that communicates with the north bridge with a serial interface similar to RDRAM. I think it is best to categorize this memory technology in the short term the same way ECC ram has been looked at in the past. As specialty ram for servers, and nothing we will see on the desktop in the near future. If Intel proves the technology's worth, there is a chance it might be something we migrate toward in the future.

 

[ForumMaster]

the main difference between DDR2 and FB-DIMM is that DDR2 uses a parrelal connection while FB-DIMM uses a serial one. this uses less power and allows greater capacity, but increases latency which is the disadvantage of FB-DIMM. FB-DIMM is used with intel's xeon processors and in SkullTrail, the CPU's use the xeon cpu socket (771) but are still desktop penryns.

 

[ViRGE]

Originally posted by: ForumMaster
the main difference between DDR2 and FB-DIMM is that DDR2 uses a parrelal connection while FB-DIMM uses a serial one. this uses less power and allows greater capacity, but increases latency which is the disadvantage of FB-DIMM. FB-DIMM is used with intel's xeon processors and in SkullTrail, the CPU's use the xeon cpu socket (771) but are still desktop penryns.

ForumMaster, some of that is right, some of that is wrong. FB-DIMMs eat more power because each one must be equipped with a memory buffer (which is basically a small processor) in order to make the still parallel-style RAM work on the serial bus. Each AMB eats about 5W on its own right now, which becomes problematic when you're talking about using a large number of these DIMMs (which is why Intel's Xeon servers are still losing to Opteron servers).

You are right about the capacity thing though.

 

[Blain]

Originally posted by: AmberClad
(yes, yet another IDF-inspired question)

This is the "General Hardware" forum.
Your question is 82% better than the...
"What parts should I buy?" threads.

 

[AmberClad]

Thanks for the answers guys, just what I was looking for (FB-DIMMs versus the regular DDR or DDR2 RAM that we use).