Best slots for 2x1GB + 2x4GB DIMMs?

[kirkbross]

What is the best DIMM configuration for 2 x 1GB sticks plus 2 x 4GB sticks, totalling 10GB.

I have a MP 2009 (4,1) 4 core with four slots and can't seem to find out which slots are which channels and whether to go 1, 1, 4, 4 or 1, 4, 1, 4.

 

[Umbongo]

What is the best DIMM configuration for 2 x 1GB sticks plus 2 x 4GB sticks, totalling 10GB.

I have a MP 2009 (4,1) 4 core with four slots and can't seem to find out which slots are which channels and whether to go 1, 1, 4, 4 or 1, 4, 1, 4.

Slot 1 - 4GB - Channel 1-Bank 0 and interleaves with slot 2.
Slot 2 - 1GB - Channel 2-Bank 0.
Slot 3 - 4GB - Channel 3-Bank 0 and interleaves with slot 4.
Slot 4 - 1GB - Channel 1-Bank 1.

 

[kirkbross]

Slot 1 - 4GB - Channel 1-Bank 0 and interleaves with slot 2.
Slot 2 - 1GB - Channel 2-Bank 0.
Slot 3 - 4GB - Channel 3-Bank 0 and interleaves with slot 4.
Slot 4 - 1GB - Channel 1-Bank 1.

Cool... I thought there were only 2 channels... or more aptly, I don't comprehend memory channel architecture.

 

[ActionableMango]

Maybe a dumb question, but if slot 1 and 2 are interleaving, and slot 3 and 4 are interleaving, shouldn't it be this:

Slot 1 - 4GB
Slot 2 - 4GB
Slot 3 - 1GB
Slot 4 - 1GB

From Apple:

 

[Umbongo]

Maybe a dumb question, but if slot 1 and 2 are interleaving, and slot 3 and 4 are interleaving, shouldn't it be this:

No, because you want balanced memory for optimal performance. So with this amount of memory you'd put 5GB on each of the two interleaving sets. You could probably use any placement combination and get the same level of real world performance to be honest.

 

[kirkbross]

Maybe a dumb question, but if slot 1 and 2 are interleaving, and slot 3 and 4 are interleaving, shouldn't it be this:

Slot 1 - 4GB
Slot 2 - 4GB
Slot 3 - 1GB
Slot 4 - 1GB

From Apple:
[url=http://i.imgur.com/0Kp8Y2X.png]Image[/URL]

I tried both ways and matched pairs was the way to go. When I staggered them 1, 4, 1, 4 it only recognized 5GB RAM total. I have it like you have it above and it recognizes all 10GB.

 

[ActionableMango]

I hesitate to give advice because I don't know what I'm talking about, but I have always read that when interleaving memory they should be matched pairs.

Granted, in a typical PC the DIMM slots are laid out such that you need to alternate the sticks in order to interleave matched pairs. In a PC I would definitely do 4,1,4,1.

But in the MP the slots must be laid out differently. The table I provided above from Apple shows the two-DIMM layout with both DIMMs placed adjacent to each other, not in alternating slots like you would in a PC.

In any case, I also have 10GB of RAM and mine are installed 4,4,1,1. Whether this is ideal or not, I don't know. I do know that all 10GB are recognized and working.

P.S. Your signature is out of date.

 

[Umbongo]

I tried both ways and matched pairs was the way to go. When I staggered them 1, 4, 1, 4 it only recognized 5GB RAM total. I have it like you have it above and it recognizes all 10GB.

As long as it works is all that matters, as I said the staggered approach wouldn't give you significant performance differences anyway. I guess the Mac Pro has issues with the placement I suggested where other LGA 1366 boards don't.

 

[Tesselator]

...I have always read that when interleaving memory they should be matched pairs.

Granted, in a typical PC the DIMM slots are laid out such that you need to alternate the sticks in order to interleave matched pairs. In a PC I would definitely do 4,1,4,1.

But in the MP the slots must be laid out differently. The table I provided above from Apple shows the two-DIMM layout with both DIMMs placed adjacent to each other, not in alternating slots like you would in a PC.

Exactly right!

 

[kirkbross]

I hesitate to give advice because I don't know what I'm talking about, but I have always read that when interleaving memory they should be matched pairs.

Granted, in a typical PC the DIMM slots are laid out such that you need to alternate the sticks in order to interleave matched pairs. In a PC I would definitely do 4,1,4,1.

But in the MP the slots must be laid out differently. The table I provided above from Apple shows the two-DIMM layout with both DIMMs placed adjacent to each other, not in alternating slots like you would in a PC.

In any case, I also have 10GB of RAM and mine are installed 4,4,1,1. Whether this is ideal or not, I don't know. I do know that all 10GB are recognized and working.

P.S. Your signature is out of date.

Actually my sig is my home MP... the MP with 10GB is at work... it's a 2009 (4,1) MP.