RAM questions: ECC, registered, ASUS K8N-E Deluxe

[uOpt]

Hi,

I got a few questions on RAM.

I always use ECC RAM in my servers, and since I often transfer parts from my workstation/gaming machine to my server later I like to get ECC RAM for my workstations, too, even if the mainboard and CPU currently in use don't support ECC. That is, if they at least accept ECC.

Now, I am getting a little confused about ECC, registered and buffered RAM. Here are some random questions:

If registered and buffered the same thing?

My understanding is that registered RAM will take an extra access cycle but will be required for some CPU and it will be required for certain setups, there might be mainboard which not require registered RAM when filling on some RAM slots, but will require it when filling all RAM slots.

Since my servers are always RAM-hungry, is it realistic to ever see a Dual-Channel PC3200 board with 8 slots that takes unregistered RAM?

In the old days I thought ECC is always registered, but apparently that's not true, it is just coincidence that most ECC modules are sold for server which also require registered, at least in maxed out RAM configurations.


The ASUS K8N-E Deluxe (NForce 3 250 GB, Athlon 64 socket 754) says it takes ECC or non-ECC RAM, but can an Athlon 64 socket 754 actually make use of it?

Can that board use 3x 1 GB unregistered RAM and run at 400 MHz? I heard that the Athlon 64 is not specified for more than 2 modules at 400 MHz and you will need to go to 333 to use three modules?

Thanks for your help!

 

[Steve]

Originally posted by: MartinCracauer
Hi,

I got a few questions on RAM.

I always use ECC RAM in my servers, and since I often transfer parts from my workstation/gaming machine to my server later I like to get ECC RAM for my workstations, too, even if the mainboard and CPU currently in use don't support ECC. That is, if they at least accept ECC.

Now, I am getting a little confused about ECC, registered and buffered RAM. Here are some random questions:

If registered and buffered the same thing? Yes

My understanding is that registered RAM will take an extra access cycle but will be required for some CPU and it will be required for certain setups, there might be mainboard which not require registered RAM when filling on some RAM slots, but will require it when filling all RAM slots.

Since my servers are always RAM-hungry, is it realistic to ever see a Dual-Channel PC3200 board with 8 slots that takes unregistered RAM? Nope. JEDEC specifies one unbuffered DIMM of DDR400 per channel. However, registered RAM does not have this limitation, and the speed grade doesn't matter a whole lot on AMD64 boards.

In the old days I thought ECC is always registered, but apparently that's not true, it is just coincidence that most ECC modules are sold for server which also require registered, at least in maxed out RAM configurations. You can have RAM that is registered, ECC, both, or neither


The ASUS K8N-E Deluxe (NForce 3 250 GB, Athlon 64 socket 754) says it takes ECC or non-ECC RAM, but can an Athlon 64 socket 754 actually make use of it? Depends on the chipset and the board's BIOS

Can that board use 3x 1 GB unregistered RAM and run at 400 MHz? I heard that the Athlon 64 is not specified for more than 2 modules at 400 MHz and you will need to go to 333 to use three modules? Even though this is out of the JEDEC spec, people have been able to get 2x400 working on one channel. Over and above that, YMMV.

Thanks for your help!

 

[Steve]

Originally posted by: MartinCracauer
My understanding is that registered RAM will take an extra access cycle but will be required for some CPU and it will be required for certain setups, there might be mainboard which not require registered RAM when filling on some RAM slots, but will require it when filling all RAM slots.

The chips on a DIMM impose an electrical load on the channel. Registered DIMMs isolate this load so it is presented as only 1 or 2 address lines, rather than up to 16. Thus, when using several high-speed DIMMs on a channel, you'll need registered DIMMs (see JEDEC spec above).

 

[uOpt]

sm, thanks!

Just to make sure, you say for a Socket 754 board I can only have one 400MHz module to be within the spec? I thought you can have 2 and need to speed down with 3?

 

[Steve]

As far as I know, s754 is single channel on the RAM, so strictly speaking it would be one DIMM of unbuffered 400 within the spec. However, many people seem to be doing fine with two. Again, YMMV.

 

[uOpt]

Well, obviously I don't get dual channel, but I don't think anything is keeping me from having two modules, running at 400 MHz combined (same speed as a single module).