ECC vs non-ECC compatibility

[ShawnD1]

I've seen several different types of ram. There's the standard memory at best buy, ECC unbuffered, ECC buffered, and ECC registered (same thing?)

Which of these are compatible? Can I put ECC memory in a non-ECC board? Can I put nECC memory in an ECC board? Can buffered and unbuffered both be used in the same motherboard? Is registered the same as buffered? Can desktop memory be used in a server motherboard? Can server memory be used in a desktop motherboard?

 

[Emulex]

for the most part server boards use registered for large dimm sizes.
servers always should run ecc.

most consumer boards do not like ecc (and/or registered).

mixing is mostly not allowed either.

an hp workstation can rock ecc or non-ecc. (xw4400 example). ddr2-667

the same motherboard in an hp low end server has a bios hardcoded to fault if ecc is not present (lame)..

you should check the chipset of the motherboard it usually references the allowed type of ram.

 

[Blain]

Stick with non-ECC unbuffered memory... Done, end of story.

 

[RebateMonger]

The answer to most of your questions is: "It depends....".

The motherboard, the BIOS, the chipset, the processor, and the memory type (EDO, SDRAM, DDR, DDR2, DDR3) can all affect the final answer.

While there are some definitional grey areas, for all practical purposes "Registered" and "Buffered" memory are the same and "Un-Registered" and "Un-Buffered" are the same. Some i7 systems will allow both to be used, but most (all?) previous motherboards only allow one or the other type of memory.

 

[Blain]

Originally posted by: RebateMonger
The answer to most of your questions is: "It depends....".

The motherboard, the BIOS, the chipset, the processor, and the memory type (EDO, SDRAM, DDR, DDR2, DDR3) can all affect the final answer.

While there are some definitional grey areas, for all practical purposes "Registered" and "Buffered" memory are the same and "Un-Registered" and "Un-Buffered" are the same. Some i7 systems will allow both to be used, but most (all?) previous motherboards only allow one or the other type of memory.

Don't leave out Low Density, High Density, FPM and RDRAM.

 

[Idontcare]

Originally posted by: ShawnD1
I've seen several different types of ram. There's the standard memory at best buy, ECC unbuffered, ECC buffered, and ECC registered (same thing?)

Which of these are compatible? Can I put ECC memory in a non-ECC board? Can I put nECC memory in an ECC board? Can buffered and unbuffered both be used in the same motherboard? Is registered the same as buffered? Can desktop memory be used in a server motherboard? Can server memory be used in a desktop motherboard?

buffered != registered, at least not according Kingston.

They claim buffering does not reduce performance whereas registering incurs a 1 cyce latency adder.

REGISTERS AND BUFFERS

Registers and buffers improve memory operation by "re-driving" control signals in the memory chips. They can be external to the memory module, or they can be located on the module itself. Having registers and buffers placed directly on the memory module, enables a system to support a greater quantity of modules. So, you're likely to find these types of modules in servers and high-end workstations. It is important to note that when upgrading, unbuffered and buffered (or registered) modules cannot be mixed.

Buffering (EDO and FPM): For EDO and fast page modules, the process of re-driving the signals is called buffering. With buffering there is no loss of performance.

Registering (SDRAM): For SDRAM, the signal driving process is called registering. Registering is similar to buffering, except that in registering, the data is clocked in and out of the register by the system clock. Registered modules are slightly slower than non-registered modules, because the registering process takes one clock cycle.

http://www.kingston.com/tools/umg/umg05b.asp

That's what Kingston had to say, not sure if it is 100% modern and relevant to today's memory landscape. Here's the specs for a modern supermicro nehalem ep mobo:

Supports up to 96 GB 1333 / 1066 / 800MHz DDR3 ECC Registered memory
Supports up to 24 GB 1333 / 1066 / 800MHz DDR3 ECC Unbuffered memory

So supermicro's vernacular definitely suggests that non-registered = unbuffered and in this mobo's case you can obviously use either registered or unbuffered in the same mobo (with unbuffered imposing a capacity limitation that registered memory does not).

edit: meant to add the link to that supermicro board http://www.supermicro.com/prod.../QPI/5500/X8DTH-6F.cfm

 

[her209]

I've used non-ECC RAM in Dells mobos with ECC capability and it works fine. It just tells you that you don't have ECC.

 

[RebateMonger]

Originally posted by: her209
I've used non-ECC RAM in Dells mobos with ECC capability and it works fine. It just tells you that you don't have ECC.

It depends on the Dell. The 400SC would allow you to use either or both at the same time. But ECC would be disabled if they were mixed.

The Dell 420SC, as I recall, would work with either one, but not mixed.

The Dell SC440 will ONLY work with ECC. The Intel-designed motherboard that the SC440 uses WILL allow mixed memory, but the Dell BIOS is modified to disallow it.