RDRAM 1066/800 compatibility

[Ironduke]

I've recently installed two additional sticks of RDRAM in a Dell Dimension I'm working on. It came with 128x2, and I put those in the second pair of memory slots and installed 256x2 in the primary pair of slots. The computer runs alot faster, programs load in seconds compared to up to a minute before the upgrade, and all four sticks show up in SiSoftware Sandra, and it shows that are all working properly.

However, when I right-click My Computer, with 768MB installed, it says I have 256MB of RAM installed. When I take out the 128x2 in the second pair of slots and put in the dummy sticks, it displays 448MB in My Computer and 512MB in Sandra. When they're installed, Sandra lists both 256MB sticks as having the same exact specifications (i.e. PC-800 40, timing, voltage, etc).

The specs/labels on the two RDRAM sticks, exactly as they appear:
Stick 1 256:

Samsung Korea 0307H 256MB / 8
MR16R1628DF0-CT9 1066-32P 102

Stick 2 256:

Samsung Korea 0244 H 256MB/8 ECC
MR18R1628AF0-CM8 800-40 101

Stick 3 & 4 128:

Samsung Korea 0244 H 256MB/8 ECC
MR18R1624DF0-CM8 800-40 012

Again, Sandra reads them all and reports no problems. It lists them all as having identical specs, despite one of the 256MB sticks being 1066-32P. The 2x256s just aren't showing up on My Computer properties, just the 2x128s when both pairs are installed, unless the 2x256 are installed with the CIMMs.

Even with My Computer properties only reading the 2x128MB sticks, I instantly noticed a massive increase in the computer's performance after installed the 2x256. So I'm guessing everything's working, but it's just not being listed on the XP OS My Computer specs? Is it just some kind of harmless quirk caused by one of the sticks being 1066?

Forgot... one of the 256MB sticks is ECC, the other is non-ECC.

 

[Fat.Clown]

maybe your computer doesn't take ECC RAM

 

[KSoD]

IT could also be that it is trying to use them as dual channel when they can not be used as dual channel.