Clear this up pls: ECC and/or REGISTERED RAM modules

[Kyanzes]

Hi! While I've spent some time rummaging around various web sites explaining ECC and Registered technology, I couldn't come up with an answer to these questions:

- If a RAM is ECC then is it also Registered as well?
- Can I use "ECC Registered" RAM in a mobo that according to its manual supports ECC but doesn't mention Registered modules?

Basically I have a 975XBX that does support ECC modules but they don't mention if these modules can be Registered as well. Help with this please.

 

[CrashX]

ECC and Registered are independent of each other. MOST (if not all) Registered RAM is ECC. But ECC RAM is not necessarily Registered.
If your machine takes Registered, then you HAVE to use it.
If your machine takes unbuffered (non-registered), then you CANNOT use Registered.
But ECC goes either way.

Consumer level chipsets do not take Registered. Only workstation and server class boards do.
So you want ECC.

 

[Peter]

ECC means that the DIMM has an extra eight bits of databus width (72 instead of 64), which allows for storing the data in a redundant manner that allows (E)rror (C)hecking and (C)orrection.

"Registered" DIMMs, as opposed to your usual "unbuffered" material, have extra chips on (registers and a clock PLL). These partially separate the RAM chips from the common bus; as a result, the DIMM poses one single electrical load "unit" to the common bus where an unbuffered DIMM counts up to 18 (one per chip). This allows two things: DIMMs with more chips on (up to 36), and boards with more DIMM slots.

Now, compatibility.

ECC does not change the electrical interface; if your mainboard doesn't use the extra eight databits, then the only bad thing is that you've paid for an extra RAM chip or two that you aren't actually using.

Registered DIMMs in contrast are electrically different from unbuffered ones. The mainboard and the RAM controller chip it uses must support that. Also, mixing registered and unbuffered DIMMs in the same system is not possible.

 

[Kyanzes]

Thank you both.