Mac Pro RAM: Pairs? Please clarify

[speekez]

Hi gang

I'm going to be ordering a BTO Mac from Apple. I'll be using it for photo retouching & Aperture. I have read Aperture loves RAM and works best with 3-4 gigs of RAM. However, I don't want to spend the $$$ on expensive Mac RAM.

My thought is to get the BTO with the stock Apple RAM configuration of 1 Gig (2 x 512MB) and then upgrade to 4gig total with third party RAM. My question is I heard the Mac Pro's should have RAM installed in matching dual pairs.... so, if I want 4Gig of RAM I should buy 4 x 1GB sticks so that I have two matching pairs, and then sell off the 2x512MB from Apple (because I shouldn't have 5GB in the computer?).

Is this how it works? Or, could I keep the 2x512MB and match it with another pair of 2x512MB (third party). And then buy two more 1gig sticks?

Any advice is appreciated!

 

[TheSpaz]

Hi gang

I'm going to be ordering a BTO Mac from Apple. I'll be using it for photo retouching & Aperture. I have read Aperture loves RAM and works best with 3-4 gigs of RAM. However, I don't want to spend the $$$ on expensive Mac RAM.

My thought is to get the BTO with the stock Apple RAM configuration of 1 Gig (2 x 512MB) and then upgrade to 4gig total with third party RAM. My question is I heard the Mac Pro's should have RAM installed in matching dual pairs.... so, if I want 4Gig of RAM I should buy 4 x 1GB sticks so that I have two matching pairs, and then sell off the 2x512MB from Apple (because I shouldn't have 5GB in the computer?).

Is this how it works? Or, could I keep the 2x512MB and match it with another pair of 2x512MB (third party). And then buy two more 1gig sticks?

Any advice is appreciated!

You can keep the 2x512MB in your computer. 2x512MB is a matching pair. All the RAM pairs must come in the same size such as 2x1GB.

You cannot however put 3x512MB in because 1 of those modules doesn't belong to a pair. Always install 2 modules at a time that are the same size. Since there's already 2x512MB in the Mac Pro, no need to take them out because they match.

So finally to answer your question, there is no need to take out the existing matching 512MB set.

Check out this diagram for all possible RAM configurations:
http://peloche.smugmug.com/photos/91749515-O.jpg

 

[adamyoshida]

From your description, I'd recommend that you start out with three Gigs of ram.

The problem with the MacPro's ram is that RDRAM, at the moment, is really, really, really expensive. I'd expect a big fall in prices PDQ.

 

[aaronw1986]

From your description, I'd recommend that you start out with three Gigs of ram.

The problem with the MacPro's ram is that RDRAM, at the moment, is really, really, really expensive. I'd expect a big fall in prices PDQ.

PDQ?

 

[eluk]

Pretty Damn Quick.

 

[speekez]

Hi Spaz

Thanks for the description and the diagram. Very helpful.

Still, for optimum performace, apple still seems to encource "matching dual pairs"... (verses just matching pairs). Meaning if I put 2x1GB on Riser A, then I should put another 2x1GB on Riser B (matching dual pairs). I think somehow this helps the MacPro take full advantage of double memory bandwidth, 256bit .... Some of the configurations in the diagram don't adhere to this rule -- that's not to say that some of the configurations in the diagram won't work, but they might not allow for optimum performance.

See Apple Doc below:

http://docs.info.apple.com/article.html?artnum=304492

 

[djray77]

Well I just got my macpro tuesday (man these are great machine btw) and it came with 2gb. If I wanted to put another 2gb in would I have to buy 4x512mb sticks? or could I just buy 2x1gb sticks? Sorry Im new to macs and want to make sure I have this right

 

[Silentwave]

From your description, I'd recommend that you start out with three Gigs of ram.

The problem with the MacPro's ram is that RDRAM, at the moment, is really, really, really expensive. I'd expect a big fall in prices PDQ.

The Mac Pro doesn't use RDRAM- it uses DDR2 667 FB-DIMM SDRAM. Prices on this are not likely to fall very much in the near future because it is a very small market and has high tolerances.

 

[eMagine]

Hi gang

I'm going to be ordering a BTO Mac from Apple. I'll be using it for photo retouching & Aperture. I have read Aperture loves RAM and works best with 3-4 gigs of RAM. However, I don't want to spend the $$$ on expensive Mac RAM.

My thought is to get the BTO with the stock Apple RAM configuration of 1 Gig (2 x 512MB) and then upgrade to 4gig total with third party RAM. My question is I heard the Mac Pro's should have RAM installed in matching dual pairs.... so, if I want 4Gig of RAM I should buy 4 x 1GB sticks so that I have two matching pairs, and then sell off the 2x512MB from Apple (because I shouldn't have 5GB in the computer?).

Is this how it works? Or, could I keep the 2x512MB and match it with another pair of 2x512MB (third party). And then buy two more 1gig sticks?

Any advice is appreciated!

you're on the right track...

 

[PmattF]

Hi Spaz
Still, for optimum performace, apple still seems to encource "matching dual pairs"... (verses just matching pairs). Meaning if I put 2x1GB on Riser A, then I should put another 2x1GB on Riser B (matching dual pairs). I think somehow this helps the MacPro take full advantage of double memory bandwidth, 256bit .... Some of the configurations in the diagram don't adhere to this rule -- that's not to say that some of the configurations in the diagram won't work, but they might not allow for optimum performance.

See Apple Doc below:

http://docs.info.apple.com/article.html?artnum=304492

That is very interesting, especially because it conflicts with this official Apple document, which explicitly says you do not need dual pairs, just pairs...
http://manuals.info.apple.com/en/MacPro_MemoryDIMM_DIY.pdf

 

[dkoralek]

That is very interesting, especially because it conflicts with this official Apple document, which explicitly says you do not need dual pairs, just pairs...
http://manuals.info.apple.com/en/MacPro_MemoryDIMM_DIY.pdf

I believe that you are mistaking what you need to do vs. what is optimum. You only _need_ pairs. But if you want to be able to access memory using full quad channel you need two pairs (one on each riser), and my guess is that having four of the same size and speed will give the best performance of all. That said, a lot of examples out there show that there isn't that great a performance gain by doing this (particularly if the decision is four dims or six which result in more RAM).


cheers.

 

[Sun Baked]

The memory requires pairs due to the dual channel operation (Using dual channel Branch 0 or 1), however adding 4x(matched DIMMs) will run it in the optional quad channel mode if the DIMMs are in the same slots on two risers (This uses Branch 0 and 1 at the same time).

However only 4 DIMMs operate/(are active) at once (all the slot 1-2 or 3-4 DIMMs) -- before switching to (looking at) the other DIMMs.

 

[TheSpaz]

The memory requires pairs due to the dual channel operation (Using dual channel Branch 0 or 1), however adding 4x(matched DIMMs) will run it in the optional quad channel mode if the DIMMs are in the same slots on two risers (This uses Branch 0 and 1 at the same time).

However only 4 DIMMs operate/(are active) at once (all the slot 1-2 or 3-4 DIMMs) -- before switching to (looking at) the other DIMMs.

*image removed*[/QUOTE]

So what you're saying is that in order to achieve true quad-channel operation, I would need 4x1GB modules to fill up the first 2 slots in Riser A and the first 2 slots in Riser B and then add the 2x512MB modules to the second 2 slots in Riser B? How much slower would it be to use the 3GB option by buying 2x1GB modules and adding them to Riser A and moving the stock 2x512MB modules to Riser B? Would it even be enough of a performance hit to even notice?

 

[PmattF]

So what you're saying is that in order to achieve true quad-channel operation, I would need 4x1GB modules to fill up the first 2 slots in Riser A and the first 2 slots in Riser B and then add the 2x512MB modules to the second 2 slots in Riser B? How much slower would it be to use the 3GB option by buying 2x1GB modules and adding them to Riser A and moving the stock 2x512MB modules to Riser B? Would it even be enough of a performance hit to even notice?

This page says you get quad channel performance simply by installing matched pairs, does not say the pairs have to be matched from each other...
http://www.anandtech.com/showdoc.aspx?i=2816&p=12

However, this page, from a later article, if I am reading it correctly, says that ideally all devices should be "dual rank", meaning 1 gig or 2 gig pieces. Which again does not say that pairs have to match each other, but does seem to imply that you would not want to use 512's (as comes from Apple with the base configuration)...
http://www.anandtech.com/showdoc.aspx?i=2832&p=1

 

[TheSpaz]

Here's a new question:

What would be the better value:
1.) Getting one more 2x512MB set and running Quad-Channel (total of 2GB)
2.) Getting one 2x1GB set and running only Dual-Channel (total of 3GB)

 

[slughead]

How many times do I have to point this out:

QUAD CHANNEL HAS NO MEASURABLE PERFORMANCE INCREASE OVER DUAL CHANNEL

It's PROVEN. Come on guys, quit suckin down the hype.

So to get 4GB, take the stock 1 and add two 512's and two 1GB's. FIN!

http://www.barefeats.com/quad09.html
We ran some typical tests from our suite of real world tests (iMovie render effect, Final Cut Pro render clip, Cinebench CPU render, Motion render RAM preview, iMaginator Core Image morph). None of them showed any gains from Quad Channel mode.

 

[PmattF]

How many times do I have to point this out:

QUAD CHANNEL HAS NO MEASURABLE PERFORMANCE INCREASE OVER DUAL CHANNEL

It's PROVEN. Come on guys, quit suckin down the hype.

So to get 4GB, take the stock 1 and add two 512's and two 1GB's. FIN!

http://www.barefeats.com/quad09.html
We ran some typical tests from our suite of real world tests (iMovie render effect, Final Cut Pro render clip, Cinebench CPU render, Motion render RAM preview, iMaginator Core Image morph). None of them showed any gains from Quad Channel mode.

This article shows that in fact there is a real (though not huge) performance gain from quad channel vs. dual channel...
http://www.anandtech.com/showdoc.aspx?i=2816&p=12

But that point is moot anyway, as you get quad channel simply by populating both risers, so the configuration you suggest is in fact quad channel.

I still have not seen any actual tests on whether using symmetrical pairs across the risers and/or avoid "single rank" 512 modules actually makes a measurable difference.

I do suspect that you are correct -- 4x512 plus 2x1gig would not be noticeably different in any way from 4x1gig. But still, I would love to see somebody actually test this.

 

[PmattF]

But that point is moot anyway, as you get quad channel simply by populating both risers, so the configuration you suggest is in fact quad channel.

Or actually, in the 4x512 + 2x1 gig scenario (i.e. in http://peloche.smugmug.com/photos/91749515-O.jpg the second configuration on the 4gb row) maybe only the first three gig would be running in quad channel, and the last gig, would be dual channel?

 

[TheSpaz]

I have a headache. I'm just gonna get the 2x1GB for right now and wait to add more when the prices are normalified.

 

[speedfreak]

you're not the only one with a headache. I'm also 1 newly Mac Pro user with the same question. Got a standaard Mac Pro and want to add 4gig of memory. Should I get 2x2gig+the standard 2x512mb or 4x1gig+the standard 2x512mb??

 

[speekez]

I have decided on 4 gigs of RAM. I am configuring a built to order and, including the prices for OWC RAM, I have found that the cheapest road to 4GB is as follows:

1. Order the stock 1GB (2x512MB) from Apple when you configure your Mac Pro. I qualify for education discount, so my total below reflects this.

2. Order another gig (2x512MB) from OWC for $219

3. Order another 2 gigs (2x1GB) from OWC for $399

Total (assuming you are ordering from Apple with an education discount) is $618. And, you have 2 slots left over.

If you order 4x512MB from Apple when configuring and the 2x1GB from OWC, the total is $668

I have not looked at other third party RAM yet -- so there may even be cheaper options than OWC.