Will intel drop FB-DIMM?

[Carlis]

The FB-DIMMs does not really seem to give a very good performance. Long latency and heat dissipation etc. One does hear rumors of their discontinuation from time to time. Is there any truth in this?

 

[Rubycon]

Stability/availability come over performance in the server environment!

 

[Carlis]

But the stability comes from using error correction I thought? Cant you have ecc ram that is not buffered? And what about two socket xeon work stations? Right now they are forced to use fb-dimm if I'm not mistaken. That extra ram capacity better be worth it...

 

[Denithor]

Basic question from the uneducated:

What is the difference?
Unbuffered, nonECC
Unbuffered, ECC (I think I've seen this somewhere)
Buffered, ECC

How does buffering & ECC work?

 

[Carlis]

Buffering ram is a technique used to increase the amount of ram that a system can use. The drawback is that the latency is higher and energy consumption tens to be higher.

ECC is error correcting ram. ECC checks bytes stored in the ram for consistency to reduce errors that are due to memory corruption.

 

[taltamir]

As of September 2006, AMD has taken FB-DIMM off their roadmap as a report earlier that the popularity of FB-DIMM is below 10%.[12] In December 2006, AMD has revealed in one of the slides that microprocessors based on the new K10 microarchtecture has the support for FB-DIMM "when appropriate".[13] In addition, AMD also developed Socket G3 Memory Extender (G3MX), which uses single buffer for every 4 modules instead of a buffer for every module, to be used by Opteron-based systems in 2009.[14]
In 2007 Intel Developer Forum, it was revealed that major memory manufacturers have no plans to extend FB-DIMM to support DDR3 SDRAM. Instead, only registered DIMM for DDR3 SDRAM had been demonstrated.[15]
In 2007 Intel demonstrated FB-DIMM with shorter latencies, CL5 and CL3, showing improvement in latencies.[16]
In August 10, 2008 Elpida Memory has announced that it will mass-produce the world's first FB-DIMM at 16 Gigabyte capacity, as from Q4 2008.[17]

 

[tcsenter]

Originally posted by: Carlis
But the stability comes from using error correction I thought? Cant you have ecc ram that is not buffered?

Registered or buffered is to protect stability in high density population scenarios. i.e. to make mission critical high density population scenarios feasible.

FB-DIMM has received something of a bad rap, partly from its coverage by some consumer-oriented hardware sites that really don't understand what someone might want with hardware that doesn't overclock or run 3DMark as well compared to enthusiast consumer hardware, but also in no small part due to poor product segmentation decisions by Intel.

There is no reason to use FB-DIMM on boards with up to four DIMMs. JEDEC standard registered DIMMs are perfectly safe there. If you enforce some configuration-dependent memory speed limits in the BIOS, unbuffered ECC DIMMs can be perfectly safe on boards with up to four DIMMs.

FB-DIMM performance looks (well, it is) terrible on two and four DIMM configurations because FB-DIMM was designed for 'many' DIMM configurations; eight, 12, 16, 24, 32, et. al. FB-DIMM performance increases as the DIMM and rank count grows (as long as utilization or load grows with it), but in low-utilization or population scenarios, the added complexity that makes FB-DIMM scalable cannot be exploited and becomes a liability.

This is a great place for FB-DIMM:

Tempest i5400PW

And what about two socket xeon work stations? Right now they are forced to use fb-dimm if I'm not mistaken.

Dual socket Xeon boards are available that accept registered DIMMs. IIRC, Intel 5000X/P/V chipset required FB-DIMM but the newer 5100 (San Clemente) supports registered DIMM.

 

[RebateMonger]

Dell has long-used unbuffered ECC memory in their lowest-end servers. These include the Dell 400SC, 420SC, 440SC, and others. But all those only have four memory slots. And Dell doesn't allow non-SPD memory timings.

I've got four 2 GB Kingston unbuffered ECC DDR2 modules in my Dell SC440 server. It just finished two days of Memtest 86+ tests without error.