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Mac Pro Ram question
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garyton
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Oct 31, 2006, 08:44 PM
 
I was just talking to a friend of mine who is ordering a new Pro for his video work and he mentioned that he had read that if you put 8GB of ram in the machine, it would be slower than the same machine with 4 GB according to some bench testing they had done. He said is was because of the Pro using latent Dimm memory.
I know there must be some answer as to why this is not true as everyone seems to favor more ram in these machines. Is it that 4 GB iof memory is like a sweet spot and more than that does slow it down or is 8Gb going to be processing and working smoother than 4Gb. I know you guys will qualify your answers based on the applications run, so lets assuse you have Final Cut Pro and Photoshop open and maybe you are on the internet or you are rendering a movie and on the internet.
thanks
     
discotronic
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Oct 31, 2006, 09:06 PM
 
You friend was probably referring to this article:

Macworld: Feature: Inside the Mac Pro: RAM
     
mduell
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Nov 4, 2006, 06:27 PM
 
Short answer: No, he's wrong.

Long answer: He's still wrong, but not far from the mark. The Mac Pro has 4 memory channels (2 channels per branch, 2 branches per system), each of which supports up to 2 modules. Assuming you put them in the right slots, going from 2 modules to 4 doubles bandwidth and leaves latency unchanged; going from 4 to 6 or 8 modules leaves bandwidth unchanged while adding slightly more latency (3-5ns minimum) only when accessing the memory in the higher numbered slots. So you can go up to 8GB RAM (possibly 16GB, but 4GB modules are hard to find) with 2GB modules without any potential for slowdown. If you have more memory than that installed, you'll only see the slowdown if your app uses memory past the first 8GB.

Rendering a movie isn't going to see a slow down; that's CPU-bound and doesn't need much memory.
Browsing the web is never going to matter, since it's not really performance critical.
Photoshop only support 4GB RAM for now, so unless you have other apps eating over 4GB RAM, you won't see any slowdown there.
Final Cut Pro could see a slowdown if you use more than the first four RAM slots.
     
dmetzcher
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Nov 4, 2006, 06:46 PM
 
To ask a semi-similar question, is it true that it's best to keep larger RAM modules closer to the first slots? For example, if you get a Mac Pro with the standard 1GB RAM, you are getting two 512MB modules. If you buy an additional two 1GB modules, you would need to install them in slot 1, and move the two 512MB modules to slot 2.

Is that correct? I ask because that's exactly the configuration I'm going to have.
Dennis R. Metzcher
MyMacBlog.com: My experiences with the Mac OS, a switcher's point of view. With a new Mac tip each week day.
     
discotronic
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Nov 4, 2006, 06:58 PM
 
Originally Posted by dmetzcher View Post
To ask a semi-similar question, is it true that it's best to keep larger RAM modules closer to the first slots? For example, if you get a Mac Pro with the standard 1GB RAM, you are getting two 512MB modules. If you buy an additional two 1GB modules, you would need to install them in slot 1, and move the two 512MB modules to slot 2.

Is that correct? I ask because that's exactly the configuration I'm going to have.
If the old way is still the right way you should leave smaller slower RAM in the first slot. Larger faster RAM in the second slot.

I don't know if that still holds true today but I don't see why it wouldn't.
     
dmetzcher
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Nov 5, 2006, 01:15 AM
 
Originally Posted by discotronic View Post
If the old way is still the right way you should leave smaller slower RAM in the first slot. Larger faster RAM in the second slot.

I don't know if that still holds true today but I don't see why it wouldn't.
When I read that the larger, faster RAM should go in the first slot, it made sense to me, because why would you want to store data on another RAM module when you don't have to do so (i.e. - if the two 512MB modules are full, you'd move to the two 1GB modules, but you would not need to do this if the two 1GB modules were in front)? Does that make sense, or am I thinking about it the wrong way? I will admit that I am not familiar with the inner-workings of RAM or how data is written to it by the OS.
Dennis R. Metzcher
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mduell
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Nov 5, 2006, 07:14 PM
 
Originally Posted by dmetzcher View Post
To ask a semi-similar question, is it true that it's best to keep larger RAM modules closer to the first slots? For example, if you get a Mac Pro with the standard 1GB RAM, you are getting two 512MB modules. If you buy an additional two 1GB modules, you would need to install them in slot 1, and move the two 512MB modules to slot 2.

Is that correct? I ask because that's exactly the configuration I'm going to have.
With only 4 modules, it doesn't matter, they're all the same distance from the memory controller (logically, not physically). With more than 4 modules, you want to put the larger modules in the closer in slots (first two slots on each card) so that you have the most capacity at the lowest latency.
     
dantewaters
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Nov 5, 2006, 08:23 PM
 
Originally Posted by mduell View Post
With only 4 modules, it doesn't matter, they're all the same distance from the memory controller (logically, not physically). With more than 4 modules, you want to put the larger modules in the closer in slots (first two slots on each card) so that you have the most capacity at the lowest latency.
SO then the question I have for you is...
I am getting a macpro within the next month and I and I want to strip
it down in order to get it a lower price (someone is investing in me)
Then I'll be added more ram.

Where should I begin? 2 x2gigs
or 2 1gigs? And since I'm buying at www.newegg.com
What kind with you recommend I see ECC or Non ECC

Thanks
     
discotronic
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Nov 5, 2006, 09:42 PM
 
Originally Posted by dantewaters View Post
SO then the question I have for you is...
I am getting a macpro within the next month and I and I want to strip
it down in order to get it a lower price (someone is investing in me)
Then I'll be added more ram.

Where should I begin? 2 x2gigs
or 2 1gigs? And since I'm buying at www.newegg.com
What kind with you recommend I see ECC or Non ECC

Thanks
The new Mac Pro takes ECC.
     
dmetzcher
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Nov 5, 2006, 09:42 PM
 
Originally Posted by dantewaters View Post
SO then the question I have for you is...
I am getting a macpro within the next month and I and I want to strip
it down in order to get it a lower price (someone is investing in me)
Then I'll be added more ram.

Where should I begin? 2 x2gigs
or 2 1gigs? And since I'm buying at Newegg.com - Buy Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!
What kind with you recommend I see ECC or Non ECC

Thanks
Here is the RAM that newegg is selling. It's what you will need. The Mac Pro is fully-buffered ECC.
CORSAIR 1GB 240-Pin DDR2 FB-DIMM Server Memory - Retail at Newegg.com
Dennis R. Metzcher
MyMacBlog.com: My experiences with the Mac OS, a switcher's point of view. With a new Mac tip each week day.
     
mduell
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Nov 5, 2006, 10:58 PM
 
Originally Posted by dantewaters View Post
SO then the question I have for you is...
I am getting a macpro within the next month and I and I want to strip
it down in order to get it a lower price (someone is investing in me)
Then I'll be added more ram.

Where should I begin? 2 x2gigs
or 2 1gigs? And since I'm buying at Newegg.com - Buy Computer Parts, PC Components, Laptop Computers, Digital Cameras and more!
What kind with you recommend I see ECC or Non ECC

Thanks
The Mac Pro takes 667Mhz FB-DIMMs, which only come with ECC.
I don't see any at Newegg with the extra-large heatsinks that the Mac Pro needs. I'd buy from Crucial: Computer memory upgrades for Apple Mac Pro Desktop/PC from Crucial.com

Originally Posted by dmetzcher View Post
Here is the RAM that newegg is selling. It's what you will need. The Mac Pro is fully-buffered ECC.
CORSAIR 1GB 240-Pin DDR2 FB-DIMM Server Memory - Retail at Newegg.com
Those don't appear to have the extra-large heatsinks.
     
dantewaters
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Nov 6, 2006, 02:02 AM
 
Originally Posted by mduell View Post
The Mac Pro takes 667Mhz FB-DIMMs, which only come with ECC.
I don't see any at Newegg with the extra-large heatsinks that the Mac Pro needs. I'd buy from Crucial: Computer memory upgrades for Apple Mac Pro Desktop/PC from Crucial.com



Those don't appear to have the extra-large heatsinks.
Those extra large heatsinks are crucial?
Also what will lower my encoding time say in DVD studio pro/ FCP
A raptor? Or is it solely Ram?
( Last edited by dantewaters; Nov 6, 2006 at 02:04 AM. Reason: wrong choice of words)
     
- - e r i k - -
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Nov 6, 2006, 02:18 AM
 
A raptor most definitely, you'll want it writing as fast as it can to the HD. Encoding is done on the CPU (and GPU in Motion) and depending on what you are encoding / rendering it will be faster than you can write to the harddrive.

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dantewaters
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Nov 6, 2006, 02:21 AM
 
So a Raptor will help in render times as well as with encoding?

Also the raptor would help if it was a capture disk?
( Last edited by dantewaters; Nov 6, 2006 at 12:07 PM. Reason: addtional info)
     
SierraDragon
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Nov 6, 2006, 04:03 AM
 
Originally Posted by mduell View Post
...Photoshop only support 4GB RAM for now, so unless you have other apps eating over 4GB RAM, you won't see any slowdown there...
I agree with all of your other observations except regarding Photoshop. The nature of Photoshop operation under OS X is such that the interaction with the OS allows PSCS2 performance to improve with up to 8 GB of RAM. My strong guess is that PSCS3 and OS 10.5 in 6 months will be capable of taking advantage of much more RAM.

Note too that PSCS2 runs under Rosetta which further increases RAM needs.

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TimmyDee51
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Nov 6, 2006, 01:50 PM
 
Originally Posted by mduell View Post
With only 4 modules, it doesn't matter, they're all the same distance from the memory controller (logically, not physically). With more than 4 modules, you want to put the larger modules in the closer in slots (first two slots on each card) so that you have the most capacity at the lowest latency.
So does that mean the larger modules should be split between the risers? Like so?


__1 GB____________512 MB__________empty_________empty__ (riser 1)


__1 GB____________512MB___________empty_________empty_ _ (riser 2)

Does that setup still achieve the parity the RAM needs? My original feeling was that the paired modules needed to go on the same riser.
Per Square Mile | A blog about density
     
Xyrrus
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Nov 6, 2006, 02:26 PM
 
Originally Posted by TimmyDee51 View Post
So does that mean the larger modules should be split between the risers? Like so?


__1 GB____________512 MB__________empty_________empty__ (riser 1)


__1 GB____________512MB___________empty_________empty_ _ (riser 2)

Does that setup still achieve the parity the RAM needs? My original feeling was that the paired modules needed to go on the same riser.
That setup is incorrect. Your original feeling is correct; RAM needs to be paired on each riser. The scenario above will either result in a) a computer not booting or b) only having 1GB available (only half the 1gig chips will be used as they're paired with 512 chips)

Connector - 512-512-empty-empty (riser 1)
Connector - 1GB-1GB-empty-empty (riser 2)

The "larger ram closer to the motherboard" refers to having all 8 slots filled. For instance, I have 4x512 in my pro. If I were to upgrade by buying 4x1GB chips, I'd want to move my 512 chips away from the motherboard.

Connector - 1GB-1GB-512-512 (r1)
Connector - 1GB-1GB-512-512 (r2)

-Xy
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TimmyDee51
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Nov 6, 2006, 02:54 PM
 
Ahhh, as I suspected. Thanks.
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dmetzcher
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Nov 6, 2006, 10:30 PM
 
Originally Posted by mduell View Post
Those don't appear to have the extra-large heatsinks.

Does the RAM that ships with the Mac Pro have the extra large heat sinks? (I've never seen the RAM tat Apple ships, so I'm asking for that reason.)
Dennis R. Metzcher
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mduell
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Nov 6, 2006, 10:30 PM
 
Originally Posted by SierraDragon View Post
I agree with all of your other observations except regarding Photoshop. The nature of Photoshop operation under OS X is such that the interaction with the OS allows PSCS2 performance to improve with up to 8 GB of RAM. My strong guess is that PSCS3 and OS 10.5 in 6 months will be capable of taking advantage of much more RAM.

Note too that PSCS2 runs under Rosetta which further increases RAM needs.
Yea I forgot about the RAMdisk-as-scratch hack; no difference after 8GB.

Originally Posted by TimmyDee51 View Post
So does that mean the larger modules should be split between the risers? Like so?


__1 GB____________512 MB__________empty_________empty__ (riser 1)


__1 GB____________512MB___________empty_________empty_ _ (riser 2)

Does that setup still achieve the parity the RAM needs? My original feeling was that the paired modules needed to go on the same riser.
You can do it like that or both 1GB on one card and both 512MB on the other card; the first two slots on each card are equal in latency.

IIRC FB-DIMMs don't need to be installed in pairs; I know you can run with just one installed.

Originally Posted by dmetzcher View Post
Does the RAM that ships with the Mac Pro have the extra large heat sinks? (I've never seen the RAM tat Apple ships, so I'm asking for that reason.)
Yes. Apple - Mac Pro - Intel Xeon and Apple - Mac Pro - Expansion show them.
     
dmetzcher
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Nov 6, 2006, 10:36 PM
 
Originally Posted by Xyrrus View Post
That setup is incorrect. Your original feeling is correct; RAM needs to be paired on each riser. The scenario above will either result in a) a computer not booting or b) only having 1GB available (only half the 1gig chips will be used as they're paired with 512 chips)

Connector - 512-512-empty-empty (riser 1)
Connector - 1GB-1GB-empty-empty (riser 2)

The "larger ram closer to the motherboard" refers to having all 8 slots filled. For instance, I have 4x512 in my pro. If I were to upgrade by buying 4x1GB chips, I'd want to move my 512 chips away from the motherboard.

Connector - 1GB-1GB-512-512 (r1)
Connector - 1GB-1GB-512-512 (r2)

-Xy
Great info. I hadn't thought of this. If the config is 2x512MB modules, and 2x1GB modules, does it matter if the 2x1GB is on riser 1 or 2? Does it matter? (Obviously, I'd have the 2x512MB on the opposite riser in slots 1 and 2 of that riser.)
Dennis R. Metzcher
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dmetzcher
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Nov 7, 2006, 12:10 AM
 
Originally Posted by mduell View Post
I see it now. All the RAM I've looked at did not have the large heat sinks on them. Guess I'm going to have to start looking at better (and more expensive) RAM.

What are the downsides to getting RAM with a smaller heat sink? I've been told by a RAM manufacturer (Omni) that it will essentially slow down the RAM if it gets hotter, rather than staying cooler. Is this true? Are there other downsides as well?
Dennis R. Metzcher
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mduell
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Nov 7, 2006, 10:12 PM
 
Originally Posted by dmetzcher View Post
I see it now. All the RAM I've looked at did not have the large heat sinks on them. Guess I'm going to have to start looking at better (and more expensive) RAM.

What are the downsides to getting RAM with a smaller heat sink? I've been told by a RAM manufacturer (Omni) that it will essentially slow down the RAM if it gets hotter, rather than staying cooler. Is this true? Are there other downsides as well?
The large heatsinks are actually Mac Pro specific; I haven't seen any other systems use them (most systems have more airflow [and more noise]).

Crucial was originally shipping memory with normal heatsinks and they discovered in their own lab testing that they were throwing ECC detectable/correctable errors. I don't know about any memory speed throttling due to temperature, but constantly correcting ECC errors will probably hurt performance a bit.
     
powerbook867
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Nov 29, 2006, 06:17 PM
 
Quick question...could I not just buy the ram from newegg and then buy some heat sinks for the ram saving me a bunch of cash compared to the crucial memory?

2 gig of ram for 500 bucks seems really high...
( Last edited by powerbook867; Nov 29, 2006 at 07:25 PM. )
Joe
     
dmetzcher
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Nov 29, 2006, 06:47 PM
 
Originally Posted by powerbook867 View Post
2 gig of ram for 500 bucks seems really high...
I second that!
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powerbook867
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Nov 29, 2006, 07:30 PM
 
I think I'm going to get the ram at new egg and grab two of these...

COOLMAX 12100 RAM Heatsink, Black - Retail at Newegg.com

Just have to wait till tomorrow to order...come on payday!
Joe
     
powerbook867
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Nov 29, 2006, 08:04 PM
 
UPDATE

I'm fairly nerdy and don't like taking chances especially with 1.89 heatsinks in a 2200 dollar box. So, I've been running the machine relatively hard all day and I thought shutting it down, popping it open and seeing how hot everything is to the touch.

I immediately opened the case after powering down, pulled out the riser cards the ram lives on and put my hands on both heat sinks. They were fairly warm, but by no means hot. Then, I stuck my pinky in the between the fins..still not hot.

Then I started thinking about the technology we've purchased and the fact that this is server ram. That does not normally come with heat sinks. And there is a fan back there pulling heat out...

I'm going to buy the heatsinks w/ my ram that I listed, but I'm not too worried about errors due to heat. I'll report back in the next couple of days with how everything is running after I get the order from Newegg.

I know, pretty unscientific..but I don't see any logical reason why we would have any problems.
Joe
     
mduell
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Dec 3, 2006, 12:44 AM
 
Originally Posted by powerbook867 View Post
UPDATE

I'm fairly nerdy and don't like taking chances especially with 1.89 heatsinks in a 2200 dollar box. So, I've been running the machine relatively hard all day and I thought shutting it down, popping it open and seeing how hot everything is to the touch.

I immediately opened the case after powering down, pulled out the riser cards the ram lives on and put my hands on both heat sinks. They were fairly warm, but by no means hot. Then, I stuck my pinky in the between the fins..still not hot.

Then I started thinking about the technology we've purchased and the fact that this is server ram. That does not normally come with heat sinks. And there is a fan back there pulling heat out...

I'm going to buy the heatsinks w/ my ram that I listed, but I'm not too worried about errors due to heat. I'll report back in the next couple of days with how everything is running after I get the order from Newegg.

I know, pretty unscientific..but I don't see any logical reason why we would have any problems.
That was... stupid.

If I recall correctly, the normal operation temperature for the AMB (memory controller in the middle of the DIMM) is about 100C.
Page 15 of this pdf shows a heat transfer simulation of an FB-DIMM, with the AMB at 93C.
( Last edited by mduell; Dec 3, 2006 at 12:52 AM. )
     
Trekkie
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Dec 3, 2006, 06:46 AM
 
For those still looking for the right RAM for their Mac Pro might I suggest the following:

Techworks by Buffalo 2GB (2 x 1GB) DDR2 667 (PC2 5300) ECC Fully Buffered Dual Channel Kit Memory for Apple Server & Mac Pro - Retail

It meets Apple's specs and has the exact same heat sink as the stock RAM. When I went shopping for RAM I narrowed it down to the Techworks linked above and the RAM offered by Transintl. Both are cheaper than Crucial with the Techworks beating out the Transintl by just a smidge. It's worth noting that unlike the Transintl offer the Crucial RAM also has the Apple approved heat sink. In the time since I've installed it my system has remained rock solid and Snappy™. If I still had any empty memory slots I would buy from them again.
-Trekkie
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