Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

12-core Mac Pro - 6 x 4GB vs. 3 x 8GB?

B

bluesteel

macrumors 6502
Original poster
Apr 5, 2007
434
74
Earth
taking into consideration that i want to enable triple channel memory mode, with about 24GB of RAM, and desire the most optimal performance out of my Mac Pro, which configuration would give me better performance on a 2010 12-core Mac Pro; 6 x 4GB modules (first three slots in both trays), or 3 x 8GB modules (first three slots in one tray)?

is there improved performance by using the first three slots in both trays over the first three slots in just one tray?

other than the capacity to have more space for additional memory, is there any other advantage to 8GB RAM modules versus 4GB modules?

i'll be working with 3D animation and visual effects. thanks for looking :)
 
It doesn't matter in terms of performance.

Remember though, if you get the 3x sticks now, you can upgrade to more down the road.
 
poot1234 said:
It doesn't matter in terms of performance.

Remember though, if you get the 3x sticks now, you can upgrade to more down the road.
Click to expand...

thanks for the advice :)

if i get 6 x 4GB, i can expand up to 40GB in the future. but then i would lose the triple channel mode, right, if i were to have 6 x 4GB and then add 2 x8GB in the future?

i can't think of a scenario where i will ever need more than 32GB of RAM. plus, with OWC RAM, the RAM i normally buy, there is a $300 difference between 24GB (6 x 4GB) and 24GB (3 x 8GB). considering the price difference, would you go with 3 x 8GB anyway?
 
bluesteel said:
thanks for the advice :)

if i get 6 x 4GB, i can expand up to 40GB in the future. but then i would lose the triple channel mode, right, if i were to have 6 x 4GB and then add 2 x8GB in the future?

i can't think of a scenario where i will ever need more than 32GB of RAM. plus, with OWC RAM, the RAM i normally buy, there is a $300 difference between 24GB (6 x 4GB) and 24GB (3 x 8GB). considering the price difference, would you go with 3 x 8GB anyway?
Click to expand...

If you truly think that it's work the extra money to have the peace of mind of knowing that you'll be able to upgrade in the future, go right ahead. If you don't plan on updating soon, I'd go with the 6x 4gb. And yes, you'd lose triple channel mode if you had anything but 3 or 6, etc.
 
poot1234 said:
It doesn't matter in terms of performance.

Remember though, if you get the 3x sticks now, you can upgrade to more down the road.
Click to expand...

Actually, that's not true. There is a slight (probably not noticeable though) increase when you have triple channel for each processor. If you have all the memory one one CPU, the other has to go through it to get to what is there, which takes longer. This is still pretty fast, so I don't think you have reason to worry with either way you go. My suggestion is that if you don't think you'll need more than 32, just get 6x4GB. Probably cheaper that way too.
 
alust2013 said:
Actually, that's not true. There is a slight (probably not noticeable though) increase when you have triple channel for each processor. If you have all the memory one one CPU, the other has to go through it to get to what is there, which takes longer.
Click to expand...

this is why i asked actually. i thought i had read somewhere in the past month about this exact same scenario. i'm pretty sure your right. i wonder if this makes a difference when rendering a heavy maya scene.
 
jav6454 said:
So crammed! Latency at 9?! I wouldn't touch it with a 10ft pole.
Click to expand...

The difference between CL7 and CL9 is practically non-existent.
You may be able to tell a minimal difference with synthetic benchmarks, in real world applications, however, there is no difference whatsoever.
 
Transporteur said:
The difference between CL7 and CL9 is practically non-existent.
You may be able to tell a minimal difference with synthetic benchmarks, in real world applications, however, there is no difference whatsoever.
Click to expand...
Yes, but the OEM memory is CL7 IIRC, and I'm not sure how the firmware would handle CL9 (may work, may not, as it may not include the full SPD timings - that is, limited to CL7, but will be able to allow 1333 to work if the CPU supports it, or 1066 otherwise).

We need a guinea pig... er.... test subject to find out (ideally, test CL 9 in ECC and non ECC RAM varieties). :D :p
 
nanofrog said:
Yes, but the OEM memory is CL7 IIRC, and I'm not sure how the firmware would handle CL9 (may work, may not, as it may not include the full SPD timings - that is, limited to CL7, but will be able to allow 1333 to work if the CPU supports it, or 1066 otherwise).
Click to expand...

Are you sure about CL7 for the 2010 Pro's?
The 1066MHz RAM in my 2009 machine indeed is CL7, I haven't seen any 1333MHz CL7 yet, though.

When I look for 1333 ECC, all of them seem to be CL9.
 
Transporteur said:
Are you sure about CL7 for the 2010 Pro's?
The 1066MHz RAM in my 2009 machine indeed is CL7, I haven't seen any 1333MHz CL7 yet, though.

When I look for 1333 ECC, all of them seem to be CL9.
Click to expand...
1333 comes in CL7, CL8, CL9, and CL10 varieties (CL7 = fastest of the JEDEC standard modules). CL9 is the most common I've seen as well.

If CL9 works, great, as CL7 will be harder to find, and more expensive (and most won't be able to tell the difference IMO). I just seemed to recall spotting an Apple page that stated CL7 for both 1066 and 1333.
 
Is the OWC 8GB 1333 RAM CL9?

Also, does anybody know if 8GB sticks are working properly in the new MP without issues even though they are unsupported by apple?
 
aquablue said:
Is the OWC 8GB 1333 RAM CL9?

Also, does anybody know if 8GB sticks are working properly in the new MP without issues even though they are unsupported by apple?
Click to expand...
I took a look at OWC's page, and it is CL9 (UDIMM = 1, 2, and 4GB sticks & RDIMM = 8GB sticks). :) So apparently Apple didn't limit the timings. :D

Good news IMO, as it will open up the ability to use other commonly available RAM, so long as it meets the rest of the specifications.
 
aquablue said:
Is the OWC 8GB 1333 RAM CL9?

Also, does anybody know if 8GB sticks are working properly in the new MP without issues even though they are unsupported by apple?
Click to expand...

OWC 8GB sticks work fine in the 2010 Mac Pro, they have been testing them for a while. I guess you can't mix the 8GB sticks with 1GB, 2GB, or 4GB chips, though....from what i've read.
 
bluesteel said:
I guess you can't mix the 8GB sticks with 1GB, 2GB, or 4GB chips, though....from what i've read.
Click to expand...

Really? Mixing 1, 2 and 4GB sticks worked at least in the previous Mac Pro.

Is there any reason why mixing these with 8GB sticks shouldn't work? :confused:

Would be a total bummer for people who don't wanna jump on the 8GB train overall.
 
Transporteur said:
Really? Mixing 1, 2 and 4GB sticks worked at least in the previous Mac Pro.

Is there any reason why mixing these with 8GB sticks shouldn't work? :confused:

Would be a total bummer for people who don't wanna jump on the 8GB train overall.
Click to expand...

I believe it is due to the density of the modules
 
Transporteur said:
Is there any reason why mixing these with 8GB sticks shouldn't work? :confused:
Click to expand...
Yes.

You cannot mix different types of DDR3.

There's non-ECC, and 2x forms of ECC; UDIMM (U = Unbuffered) and RDIMM (R= Registered). There's even differences that you cannot mix the 4GB with 1 or 2GB sticks due to the thermal sensors, according to OWC (presume the lack of thermal sensors on the smaller sticks, as they won't get hot enough to need them = cost savings).

So you have to keep it all the same; 1 - 2GB UDIMM's (mixable), 4GB UDIMM's only, 8GB RDIMM's only, or all non-ECC DDR3 only (typical DDR3 desktop memory).

Hope this helps. :)
 
nanofrog said:
So you have to keep it all the same; 1 - 2GB UDIMM's (mixable), 4GB UDIMM's only, 8GB RDIMM's only, or all non-ECC DDR3 only (typical DDR3 desktop memory).

Hope this helps. :)
Click to expand...

Wait a second, that means that I can't even put 4GB sticks (assuming they would be the same type as the existing ones) in my Pro which currently uses 2GB sticks?

Wow! Bummer!

I always thought that was possible.
 
Transporteur said:
Wait a second, that means that I can't even put 4GB sticks (assuming they would be the same type as the existing ones) in my Pro which currently uses 2GB sticks?

Wow! Bummer!

I always thought that was possible.
Click to expand...
Not according to OWC. :(

The only thing that makes sense to me (as 1,2, and 4GB sticks are UDIMM), is that the smaller capacity sticks (1 & 2GB) don't have the thermal diodes on them (make sense from a production cost POV, as the smaller capacity DIMM's won't need them).

Sucks, but it's the most logical explaination.
 
nanofrog said:
Not according to OWC. :(
Click to expand...

Well, glad that we talked about that as I'm constantly looking for a good deal on two 4GB sticks. I think my search is done. :p Thanks for the heads up!

nanofrog said:
The only thing that makes sense to me (as 1,2, and 4GB sticks are UDIMM), is that the smaller capacity sticks (1 & 2GB) don't have the thermal diodes on them (make sense from a production cost POV, as the smaller capacity DIMM's won't need them).

Sucks, but it's the most logical explaination.
Click to expand...

Why exactly do the smaller sticks not need a thermal diode?

AFAIK the Hynix memory my Pro uses (Apple supplied RAM) has thermal sensors, at least iStat menus reads them. Actually, I thought that RAM that is supposed to work in a Pro requires thermal sensors (reason being the SMC).
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back