[someone]

Hi there,

I have 2 1GB FB-DIMMs and 2 512MB sticks for my mac pro. Label the slots A[1-4] and B[1-4], with 1 being closest to the logic board (i.e. to the left). Here's how they are currently:

A1: 1GB
A2: 1GB
B1: 512MB
B2: 512MB

But I've heard others say that you're supposed to "Match the same brand and size memory in corresponding slots (eg slot 1 on riser card A with slot 1 on riser card B)." (diglloyd: All About Apple Mac Pro Memory). So should I be doing this instead?

A1: 1 GB
A2: 512MB
B1: 1 GB
B2: 512MB

Or is there a third, even better option?

Thanks

[imitchellg5]

You should use same brand just to be safe to avoid any future maladies. If you have a kernel panic in the future caused by RAM, it is easier to have RAM made by the same manufacturer. It doesn't really matter what order you put it in, but most people do biggest to smallest.

[mduell]

You have the Apple recommended setup, which I agree with. But it may not matter, and those two setups may be the same performance-wise. In theory the 4 inside slots are all equal (being the first module on different channels).
Also the link in your post is broken.

Originally Posted by imitchellg5 

You should use same brand just to be safe to avoid any future maladies. If you have a kernel panic in the future caused by RAM, it is easier to have RAM made by the same manufacturer. It doesn't really matter what order you put it in, but most people do biggest to smallest.

It does matter; the 2 slots "closer in" on each riser have lower (and equal) latency, so you want the larger capacity in them.

[nerd]

I have mine like they say in the link you posted. I didn't think the Mac Pro would boot if the memory was configured like you have it in your second configuration. I thought you had to have 2 matching sticks on a riser, my Mac Pro come with the 2 512s in A1 and A2. So I would say your correct in your config as well.

You will see the memory bandwidth increase if you matched the same config on the second riser, so if you got 2 more 1GB modules and put them on B1 and B2 then you would be seeing a nice speed up of the memory bandwidth.

Here's how I have mine configured.

A1: 1GB
A2: 1GB
B1: 1GB
B2: 1GB

A3: 512MB
A4: 512MB
B3: 512MB
B4: 512MB

[twilbert]

My configuration on 2.66 mh Mac Pro is:

A1: 512 mb
A2: 512 mb
B1: 512 mb
B2: 512 mb

A3: 1gb
A4: Empty
B3: 1 gb

My original was 2gb (4x512)

Added the 2gb (2x1) in A3 & B3. These slots are recognixed as empty.

Help!!

[twilbert]

B4 also empty

sorry

[someone]

move B3 to A4

[twilbert]

Thanks

That did it

[mduell]

You want the 2x1GB in A1 A2 and the 4x512MB in B1 B2 B3 B4.