More CPU or more RAM ?

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
Hi All,

I have been wanting a Mac Pro for a long long time, and I am about ready to pull the trigger (this week hopefully).
However I have one last hesitation, I was going to the quad-core 2.9ghz with 8 gig of ram (4x2), but I just realized that through some special offer from where I am I could get for about 10% less money a quad-core 2.6ghz with 12gig of ram (3x4)...

So which is best ? I do mostly photoshop + lightroom + DxO + Photomatix, etc. plus the occasional gaming, movie watching, programming, etc.

I am kind on a budget, therefore 10% price difference is not that negligeable, but what worries me, is that I could go now with 8g et upgrade later... but if I go with the 2.6ghz I won't be able to upgrade to the 2.9ghz at all....

What do you guys think ? I really don't know at this point...

Alex
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
Right, I completely agree... but in the end the cost of upgrade from 8g to 12g will be really big as I need to change all the dimm to get there.

Alex
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
Maybe I can go at it some other way...

how would the mac pro work if I bought the standard 3g and then by one additional 4g in one dim ? having effectively 1g 1g 1g 4g ?

Would the performance be really disastrous ? is it even possible ?

Because if I do that I get 7g, which is approximatively the same a 8g, but I already get 1x4g which significantly reduce the cost of upgrading to 12g late (by 40%) and more over I could upgrade gradually by replacing 1 by 1 the 1g by 4g dimm...

How is that idea ?

Alex
 

MythicFrost

macrumors 68040
Mar 11, 2009
3,929
38
Australia
Can you afford 8x2GB modules from otherworldcomputing.com? I think it's like $50 per 2GB module...
8 of any of the same type of module will get you the most throughput I think.

Kind Regards
 

dsiew81

macrumors member
Jun 29, 2007
62
0
Both components will drop in price, but getting affordable RAM is easier than CPUs. If you want processing power, then choose CPU over RAM especially since the CPUs are higher-clocked and as mentioned, you can easily add more RAM.
 

nanofrog

macrumors G4
May 6, 2008
11,718
2
Get the higher clock now, even if you have to short the RAM a bit to do so. Upgrade the memory later, as it's easier, and will get cheaper as well. You might even be able to hold out for larger DIMM's (8 & 16GB will be available shortly, and help push the prices of the 4GB sticks down out of the stratosphere). It makes more than 8GB RAM practical in the near future, if you need it.
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
Can you afford 8x2GB modules from otherworldcomputing.com? I think it's like $50 per 2GB module...
8 of any of the same type of module will get you the most throughput I think.

Kind Regards
Hi,

Yes I could, but I think it's a little bit stupid to buy 4x2GB (I am only taking the quad cord, therefore only 4 slots), because when I want to buy 12g a least in the future. I will need to sell back (throwing away money) the 4x2g to get 3x4g...

So I was thinking that instead of spending the money on 4x2g, I could go with the minimum apple is offering (3x1g) and buy just one 1x4g from OWC which basically cost the same as buying 4x2g, but I don't have to throw away the 4x2g if I want to upgrade in 6month...

How would the macpro react with 3x1g + 1x4g ?

Alex
 

diazj3

macrumors 6502a
Jan 19, 2008
879
135
I went through this decision 4 weeks ago - made lots of research. For what I gathered, basically all benchmarks concurred that the 2.93 was less bang for the buck. All concluded that the 20% extra cost was not worth it in either the Quad and Octo machines, being the 2.66 the "sweet spot" in value for both configs. According to the benchmarks, the theoretical 8% increase in speed wasn't noticeable in real world use.

I went for the 2.66 Quad (I don't need the 8-core, since I don't render video, 3D or huge math analysis 24/7) and invested the $500 difference in a 6GB RAM upgrade and a couple of hard drives (fast Samsung F3 and "green" Samsung F2)- which reportedly help speed more than the CPU upgrade to 2.93... and still got enough $ left for a nice webcam or other needed gadget.

Now - about the RAM, I learned that (because it operates in triple and quadruple channel) it should be used in sets of 3 or 4 equal sticks for optimal performance... so 7GB as you plan might not work - or at least won't report any benefits. Either do 3, 6, 8 or 16 (in a quad with 4 slots).

Hope this helps.
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
I went through this decision 4 weeks ago - made lots of research. For what I gathered, basically all benchmarks concurred that the 2.93 was less bang for the buck. All concluded that the 20% extra cost was not worth it in either the Quad and Octo machines, being the 2.66 the "sweet spot" in value. According to the benchmarks, the theoretical 8% increase in speed wasn't noticeable in real world use.

I went for the 2.66 Quad, and spent the extra $ in extra RAM and a couple of hard drives (fast Samsung F3 and "green" Samsung F2)- which reportedly help speed more than the CPU upgrade to 2.93.

Now - about the RAM, I learned that (because it operates in triple and quadruple channel) it should be used in sets of 3 or 4 equal sticks for optimal performance... so 7GB as you plan might not work - or at least won't report any benefits. Either do 3, 6, 8 or 16 (in a quad with 4 slots).

Hope this helps.
You probably have a good point for the 2.66 vs 2.93... it's "only" 8% increase in performance ? Because in theory there is almost 17% difference in usable Mhz ?

For the RAM, I agree and understand that it won't be optimum... but in my mind it's just a temporary solution until I upgrade to my desired 3x4g configuration... but if it simply works it would be the optimum temporary alternative in term of cost.

Alex
 

diazj3

macrumors 6502a
Jan 19, 2008
879
135
... it's "only" 8% increase in performance ? Because in theory there is almost 17% difference in usable Mhz ?
That's what was measured in the different benchmarks. You can check the ones posted in Barefeats and MacWorld, plus there are plenty of threads about this right here.

For the RAM ... it's just a temporary solution until I upgrade to my desired 3x4g configuration... but if it simply works it would be the optimum temporary alternative in term of cost.
IMHO, at the end, hardware decisions must be based on real needs and intended use... otherwise it's just basement bragging and/or a waste of money. Some say you're best off buying the optimal config and upgrading machines often. By the time the 4GB RAM sticks drop to the current/equivalent 2GB price, there will be another technology that will offset their edge...

So let me be curious (and I don't mean to bug you)... what is it exactly that you do to need 16GB RAM? (but can manage with 6 for now?)... I would totally understand it if you needed or were considering an 8-Core. If that much RAM it's vital for your line of work, wouldn't you be better off with a SSD drive as scratch drive...?

cheers!
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
That's what was measured in the different benchmarks. You can check the ones posted in Barefeats and MacWorld, plus there are plenty of threads about this right here.



IMHO, at the end, hardware decisions must be based on real needs and intended use... otherwise it's just basement bragging and/or a waste of money. Some say you're best off buying the optimal config and upgrading machines often. By the time the 4GB RAM sticks drop to the current/equivalent 2GB price, there will be another technology that will offset their edge...

So let me be curious: what is it that you do to need 16GB RAM? (but can manage with 6 for now?)... If it's vital for your line of work, wouldn't you be better off with a SSD drive as scratch disk...?

cheers!

Well you ask the good questions :)

I do photography. I often "play" with gigantic panoramas (HDR, 60-70 photo each) which gives working files of ~ 1g per files...

I also have some needs to have a virtual machine for some other OSes which tend to eat quite a bit of RAM.

Regarding the SSD, I already bought one, the new Intel X-25 160g, I am just waiting on the mac pro to install it in :)
And I also bought a pseudo RAID-Hardware (rocket raid) for my 4x1TB waiting for the mac pro as well :).

So right now I am using a Macbook Pro with 4g of ram, and I wanted to go at least twice (hence the 8g) but I am thinking that in the long run (since I do everything with my mac, browsing, movies, etc.) that going 12g would not be that much of a waste. But as I am not really how 8g is going to act (vs the 4g that I have) I want to give myself options to upgrade later. And I just feel that if I buy 2x4g, this is money going to the drain, since I can't reuse any of it if I feel the need to upgrade in 6 months.

Alex
 

Sun Baked

macrumors G5
May 19, 2002
14,874
57
Maybe I can go at it some other way...

how would the mac pro work if I bought the standard 3g and then by one additional 4g in one dim ? having effectively 1g 1g 1g 4g ?

Alex
From Apple...
The processor’s memory controller has three memory channels. DIMM slots 1 and 2 have their own channels; slots 3 and 4 share a channel.

For optimal memory bandwidth, all three memory channels should be used, and memory should be balanced across the three channels.

Note: Populating slot 4 slightly drops maximum memory bandwidth, but depending on the applications used, overall system performance may benefit from the larger amount of memory.
Apple notes you can probably run with 2 dimms, and based on some of the boot patterns with people mismatching memory on the Mac Pros and still getting them to boot, you'd likely not get 3x1g + 1x4g to work.
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
From Apple...
Apple notes you can probably run with 2 dimms, and based on some of the boot patterns with people mismatching memory on the Mac Pros and still getting them to boot, you might get away with 2x1 and 2x4 -- likely not 3x1 + 1x4.
Right.. but it does not say if having 2 different ram size on slot 3 & 4 would work...

Having 3x1g on Slot 1 to 3 would good (bandwidth wise), adding a 4g in the 4th slot would bring me the minimum "amount" needed while dropping a bit the bandwidth, I get that... but I don't know if it would simply work without even talking about optimal performance.

Alex
 

diazj3

macrumors 6502a
Jan 19, 2008
879
135
Well you ask the good questions :)

I do photography. I often "play" with gigantic panoramas (HDR, 60-70 photo each) which gives working files of ~ 1g per files...

I also have some needs to have a virtual machine for some other OSes which tend to eat quite a bit of RAM.

Regarding the SSD, I already bought one, the new Intel X-25 160g, I am just waiting on the mac pro to install it in :)
And I also bought a pseudo RAID-Hardware (rocket raid) for my 4x1TB waiting for the mac pro as well :).
Wow - that's big... it sounds it'll be an awesome machine!!! with the SSD & 1TB RAID.

Then I'd say... get the 2.93 AND the 16GB RAM... maybe you do need every single Ghz bit you can get to really exploit and manage the data & speed from the 16GB RAM, the 160GB SSD and the 4TB RAID arrange.

Congrats on your new beast!
 

Sun Baked

macrumors G5
May 19, 2002
14,874
57
Right.. but it does not say if having 2 different ram size on slot 3 & 4 would work...
Likely not, they share a single channel ... but people have got Intel Macs to boot with worse memory pairings.

However, since it is likely hooked into that shared channel via memory switching ... could possibly work.

Unlike 1 & 2 which look at both DIMMs at the same time, entirely possible only a single DIMM in 3 or 4 is active at any time. Which gives you the switching active DIMM performance penalty.

---

That is just a guest based on how Apple tended to add DIMM slots in the past ... don't have any firm idea how they did it with this current machine.

Plug and pray always seems to be the first victims method. All depends on the memory check routine and whether it kicks it out if pairs are mismatched.
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
Likely not, they share a single channel ... but people have got Intel Macs to boot with worse memory pairings.

However, since it is likely hooked into that shared channel via memory switching ... could possibly work.

Unlike 1 & 2 which look at both DIMMs at the same time, entirely possible only a single DIMM in 3 or 4 is active at any time. Which gives you the switching active DIMM performance penalty.

---

That is just a guest based on how Apple tended to add DIMM slots in the past ... don't have any firm idea how they did it with this current machine.

Plug and pray always seems to be the first victims method. All depends on the memory check routine and whether it kicks it out if pairs are mismatched.
Thanks for the feedback... I am really curious about this, maybe I'll start a new thread...
Also base on your experience, if I was doing 1g + 1g + 4g + 4g would that work "better" ?

Alex
 

gugucom

macrumors 68020
May 21, 2009
2,136
0
Munich, Germany
There are only two speed steps to consider.

1. RAM working in triple channel or slower

2. The Mac falling back to disk due to lack of RAM capacity


Naturally your machine maintains it's highest speed at 3,6,12 and 24 GB using only three of the available RAM sockets. If you start seeing page outs and your machine starts to use the disks for storage you would be better of to go to a higher triple or if you cannot afford that to fill the 4th RAM slot.

I do not do photographic work and have no experience but from your description I would think that under 6 GB you can be more concerned with falling back to disk speed. Between 6 and 12 GB you are probably good enough to be concerned to make that step in one go. But don't come back and complain about bad advise if it turns out different. One really cannot make good predictions without getting some experience.
 

Sun Baked

macrumors G5
May 19, 2002
14,874
57
Thanks for the feedback... I am really curious about this, maybe I'll start a new thread...
Also base on your experience, if I was doing 1g + 1g + 4g + 4g would that work "better" ?

Alex
http://www.barefeats.com/nehal02.html

Note: If you install different-size DIMMs in your Mac Pro, follow the order in the table. If the DIMM configuration you install doesn’t provide optimized performance, the Memory Slot Utility appears onscreen and recommends an improved configuration.

To use the utility again, go to /System/Library/CoreServices/Memory Slot Utility
 

MythicFrost

macrumors 68040
Mar 11, 2009
3,929
38
Australia
Ah I was thinking of my Mac Pro when saying 8x2GB, so for the best results with the 09, you should have three identical modules in both risers?

Kind Regards
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
Ah I was thinking of my Mac Pro when saying 8x2GB, so for the best results with the 09, you should have three identical modules in both risers?

Kind Regards

Yes I know that... and for the moment I am not concerned about optimal performance... I know that the best would be to get 3x4g, but I can't afford it for the moment.

Therefore I am looking at alternative solutions to get there in a little while whitouth throwing out perfectly good 2g ram module that I won't be able to re-utilize if I upgrade to 12g


So buying the default 3x1g + adding 1x4g allow me to buy a 2nd 1x4g in 2 months, and a third one in 4... and I am happy because I did not cash out for 3x2g that will be used for nothing later on...

So the main question remains to me, will 3x1g + 4x1g work at all not even talking about performance.

Thanks,

Alex
 

nanofrog

macrumors G4
May 6, 2008
11,718
2
Yes I know that... and for the moment I am not concerned about optimal performance... I know that the best would be to get 3x4g, but I can't afford it for the moment.

Therefore I am looking at alternative solutions to get there in a little while whitouth throwing out perfectly good 2g ram module that I won't be able to re-utilize if I upgrade to 12g


So buying the default 3x1g + adding 1x4g allow me to buy a 2nd 1x4g in 2 months, and a third one in 4... and I am happy because I did not cash out for 3x2g that will be used for nothing later on...

So the main question remains to me, will 3x1g + 4x1g work at all not even talking about performance.

Thanks,

Alex
You'd want to hang on to the OEM memory at least until Apple Care runs out, just in case you ever have to get a replacement system from Apple. They won't transfer 3rd party upgrades for you, so add-ons can essentially just "vanish" when you get the new machine if you don't remove them first.

Apple only sends a duplicate or equivalent (if out of production & none available) of the original system order.
 

aponsin

macrumors member
Original poster
Mar 28, 2009
75
5
You'd want to hang on to the OEM memory at least until Apple Care runs out, just in case you ever have to get a replacement system from Apple. They won't transfer 3rd party upgrades for you, so add-ons can essentially just "vanish" when you get the new machine if you don't remove them first.

Apple only sends a duplicate or equivalent (if out of production & none available) of the original system order.
I see, that's a good point :) Thanks.
 

MythicFrost

macrumors 68040
Mar 11, 2009
3,929
38
Australia
They shouldn't be able to do that!
If I get my Mac Pro replaced, they should transfer the upgrades or pack the other stuff up safely in a box and give it to me. There would be hell to pay if they took my SSD (+ Data), graphics card and additional RAM.

I find that really weird, good to know though.