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Arrangement of RAM

I

inigel

macrumors regular
Original poster
Mar 14, 2008
234
0
No where
A mate of mine had a look at the RAM configuration of my Mac Pro (4x2GB, 2x1GB), telling me it was completely wrong. After the argument we had I decided to take a look at the Apple manual and see what they recommended and I think I followed the instructions right.

http://idisk.mac.com/barra_240t/Public/dimm_diagram.png

There is a diagram of my interpretation, have I followed the instructions properly or is my mate being a know-it-all?
 
inigel said:
A mate of mine had a look at the RAM configuration of my Mac Pro (4x2GB, 2x1GB), telling me it was completely wrong. After the argument we had I decided to take a look at the Apple manual and see what they recommended and I think I followed the instructions right.

http://idisk.mac.com/barra_240t/Public/dimm_diagram.png

There is a diagram of my interpretation, have I followed the instructions properly or is my mate being a know-it-all?
Click to expand...

Looks about right given what configurations other people
here have used. I wonder if this is ok too:

dimms.png

What confuses me is where the FB-DIMMs can be paired.
In your diagram it looks like you're pairing on the same
riser, but the new MPs come with 2 FB-DIMMS paired
across different risers.
 
Infrared said:
Looks about right given what configurations other people
here have used. I wonder if this is ok too:

View attachment 108331

What confuses me is where the FB-DIMMs can be paired.
In your diagram it looks like you're pairing on the same
riser, but the new MPs come with 2 FB-DIMMS paired
across different risers.
Click to expand...

No, that's bad, the 1G chips have to be installed in pairs. The original image is the correct one.
 
IgnatiusTheKing said:
What about this?

If it's wrong, can someone explain to me why? Thanks.
Click to expand...

This is exactly how the Apple Store Genius Bar told me to install it.

[Edit: I had to lug my beast down to the Apple Store Genius Bar to get my bad Stock Apple Ram replaced under warranty]
 
IgnatiusTheKing said:
What about this?

If it's wrong, can someone explain to me why? Thanks.
Click to expand...

The 2GB sticks should be installed as matched pairs. That means put the 2GB sticks in Risers A & B, slots 1 & 2. Place the 1GB sticks in Riser A slots 3 & 4. The Genius Bar guy is wrong on this one.
 
Page 44 of the "Everything Mac" booklet that comes along with the Mac Pro explains this, pretty clearly in my eyes.

Why are there so many threads on this issue? Is it the "ordering" of the pairs of memory that is questionable to some?
 
If I remember correctly there are some slight differences between the original and the 2008 Mac Pro concerning the memory configuration.

For the 2008 model, If you add a pair of RAM modules, you have to put the two modules on the same riser.

The only exception is the default config with only two modules in total
 
macz1 said:
If I remember correctly there are some slight differences between the original and the 2008 Mac Pro concerning the memory configuration.

For the 2008 model, If you add a pair of RAM modules, you have to put the two modules on the same riser.

The only exception is the default config with only two modules in total
Click to expand...

I think what's lacking for me is an understanding of why it has to
be that way. At the moment it's a case of reading this person saying
this thing, that person saying that, and sort of guessing who is
most credible. So I'm going to Google a bit and see if I can find
out how these memory controllers actually work, so I can reason
from first principles, so to speak.
 
I read here that the system is faster if all slots are filled (7.5 opposed to 6.8). In other words, 8x1GB is better than 4X2GB. With that in mind, I wanted to put 12 GB - 4x2GB and 4x1GB. The question is - if I buy 4x2GB and 2x1GB from OWC, will that work with the the 2x1GB that Apple ships out?
 
Mac-HD said:
I read here that the system is faster if all slots are filled (7.5 opposed to 6.8). In other words, 8x1GB is better than 4X2GB. With that in mind, I wanted to put 12 GB - 4x2GB and 4x1GB. The question is - if I buy 4x2GB and 2x1GB from OWC, will that work with the the 2x1GB that Apple ships out?
Click to expand...

It is my understanding it will as long as everything is paired up. Look at the link above
 
Hang on when i got my Mac Pro last week (BTO from Apple) the standard 2GB came it came with was configured with 1GB stick on each riser.

Is that wrong? i just assumed as that was the way it came that that is the way it should stay. Should i have both sticks on riser a and leave riser b empty? (I will be getting more RAM when i have a bit of spare money....)
 
No, having just two sticks is a special case where it is optimal to have the sticls on different risers. Once you add ram, then you will change the arrangement.
 
aaronw1986 said:
No, having just two sticks is a special case where it is optimal to have the sticls on different risers. Once you add ram, then you will change the arrangement.
Click to expand...

What is it that allows that special case to work?
 
Soop53 said:
This link pretty much answers any question!;)
Click to expand...

NO! For Early 2008 Mac Pros, this diagram is WRONG. The diagram available via the "link" is for earlier Mac Pros.

Case and point - all early 2008 Mac Pros that ship from the factory with 2GB of memory ship with one GB on the top card and one on the bottom. The Early 2008 optimized memory configs are DIFFERENT than earlier models - DO NOT go by this diagram if you have a early 2008 Mac Pro.
 
Lumpydog said:
NO! For Early 2008 Mac Pros, this diagram is WRONG. The diagram available via the "link" is for earlier Mac Pros.

Case and point - all early 2008 Mac Pros that ship from the factory with 2GB of memory ship with one GB on the top card and one on the bottom. The Early 2008 optimized memory configs are DIFFERENT than earlier models - DO NOT go by this diagram if you have a early 2008 Mac Pro.
Click to expand...

So the linked diagram would be correct for a 2.66 MacPro, right? I ask because that is what I have and the Apple Genius has me keep the 2X512k in riser A and the 2X2GB under them in riser B. That diagram shows the 2X2GB in riser A with the smaller memory below. Would this be better to put the big sticks in riser A then?
 
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