On Fri, 5 Aug 2005 13:04:19 +0000 (UTC), david.madore@ens.fr (David
Madore) wrote:

>Hi,
>
>This _must_ be a FAQ, yet I couldn't find the answer anywhere (or
>rather, I found completely conflicting answers):
>
>Will Registered ECC RAM work on a motherboard that calls for
>"Unbuffered non-ECC / ECC RAM"?

Almost certainly not.

>Many FAQs explain the difference between registered and unbuffered
>RAM, and between ECC and non-ECC, and imply that certain configs
>require registered RAM (e.g., dual processor motherboards, any kind of
>Opteron, etc.), but the point about certain motherboards requiring
>_unbuffered_ RAM is not made.

As a general rule of thumb a motherboard either requires registered
memory or it requires unregistered memory. These days there are very
few boards that will work with either (older boards are a bit
different in this regard, but for new boards it usually one or the
other).

> The motherboard's manual also makes no
>particular warning (whereas it mentions a whole lot of things that
>will _not_ work, such as trying to use DDR instead of DDR2).

To put DDR memory in that board would require a hammer... don't do it!

> I am
>also told that ECC RAM will work on non-ECC motherboards.

Generally speaking yes, though that's definitely not a sure-thing.
Usually if you put ECC memory in a board that doesn't support ECC it
will just ignore the extra chip and work exactly as if it was non-ECC
memory. However you are taking a bit of a chance doing so.

>The reason for my concern is that it seems extremely difficult, if not
>downright impossible, to get Unbuffered ECC RAM - let alone DDR2
>Unbuffered ECC - here; in fact, one broker could not even be convinced
>that it exists.

It most definitely does exit. There's absolutely no requirement for
ECC memory to be registered/buffered. In fact, there's absolutely no
requirement for registered memory to be ECC, though non-ECC registered
memory is EXTREMELY rare.

Here's a link to some DDR2 667 ECC/unbuffered memory:

http://www.crucial.com/store/partspe...LE=CT6472AA667

Seems like this is what you were looking for? Crucial also carries
1GB parts as well as some DDR2 553 memory that should fit the bill.

> It's most unfortunate having a motherboard that
>supports a kind of memory that is impossible to find!

Your motherboard does also support bog-standard non-registered,
non-ECC memory, so if ECC is not a requirement for your applications
you could go for that. If not, Crucial can definitely provide you
with memory that will work for you, though perhaps not with the
maximum speed DDR2 800. Kingston also has non-registered ECC memory,
as should most of the other bigger memory companies.

> On the other
>hand, Registered ECC is relatively easy to find. (Also, it seems to
>me that it would be massively stupid not to allow for the mere extra
>clock cycle delay it takes to make Registered RAM usable on all
>motherboards, but, well, stupidity is hardly ever a reason for things
>being otherwise.)

There's more to it than just an extra clock cycle. It's rather tricky
(read: extra cost) to make a board that support BOTH registered and
non-registered memory these days. As such you're pretty much left
with one or the other.

-------------
Tony Hill
hilla <underscore> 20 <at> yahoo <dot> ca