[SOLVED] Mac memory 3 sticks else performance hit - true?

[need2sleep]

I have a MacPro, mid-2010, 6 core, 3.33 Ghz. I was told at the time of purchase in 2010 that I needed to confine my memory to 3 sticks; anything else would incur a performance hit. I have 4 slots.

Machine runs original O/S, 10.6.8.

3 sticks would limit memory configurations to 6Gb, 12Gb, or 24Gb.

Is this still true? Was it ever true?

OWC tells me their products include the "Apple Specified
Thermal Sensor" Do all memory sticks have this sensor?

OWC also says that "Apple MacPro "Nehalem" & "Westmere" models utilize high-performance multi-
channel memory addressing that benefits from the installation of matched memory sets," which
flies in the face of the 3 stick rule.

Crucial does not say anything about either of these two topics.

Thanks,

 

[Dunlop0078]

Well I can tell you thats not true with a pc, and i dont see why that would be true with a mac. Unless apple for some reason decided they dont want you to have a 4th memory stick because they like to control everything. They do crap like that all the time so it wouldn't surprise me. Who told you that a 4th memory stick would hurt performance? How much ram do you have now? How much memory can you support? They may have just meant it wouldn't add to performance because your machine can only support so much ram.

 

[need2sleep]

> Who told you that a 4th memory stick would hurt performance?
I don't have a source; only that it was well known at the time.

How much ram do you have now?
I have 3 sticks of 2Gb, so 6Gb total.

How much memory can you support?
32 Gb if all 4 slots are filled; max 8Gb per slot.

 

[Dunlop0078]

> Who told you that a 4th memory stick would hurt performance?
I don't have a source; only that it was well known at the time.

How much ram do you have now?
I have 3 sticks of 2Gb, so 6Gb total.

How much memory can you support?
32 Gb if all 4 slots are filled; max 8Gb per slot.

Well im going to go out on a limb and say thats not right. I cant find anything about it on google. You should be able to populate all four slots and have them work as intended. I dont think any motherboard manufacturer would even put a forth memory slot if it was going to hurt performance when you populated it, that doesn't make sense.

 

[need2sleep]

http://macperformanceguide.com/Mac-Upgrade-MacPro-Memory.html
"Top memory performance (by a few percent speed on real tasks) is realized with triple channel memory by sticking with 3 modules (4-slot machines) or 6 modules (8 slot machines)."

http://forums.macrumors.com/threads/performance-hit-with-two-ram-sticks.1042845/
The poster was asking whether installing 2 sticks now and 1 stick later would incur a huge performance hit now. The answer was,
"The difference is pretty negligible in real world as most apps cannot take advantage of such high memory bandwidth" (as occurs when you install 3 sticks).

http://mac.bigresource.com/Mac-Pro-Nehalem-memory-6-is-better-than-8-sticks--93EBkmZiZ.html
Combine read/write memory test dropped performance by 1/3 when increasing memory from (a multiple of 3 sticks to a multiple of 4 sticks).

Judging from these 3 articles, it looks like I'll stick with my rule of 3, for now.
I forgot to mention, we're using this machine for video editing, so the programs we use have a better than average (user) chance to take advantage of the memory bandwidth.

 

[k1114]

It's dumb for them to put 4 slots on a triple channel system. You don't see that on pc where it's usually 6 slots. You might not get a decrease in performance. While bandwidth lowers, performance can increase from having more ram.

 

[McHenryB]

Your computer would obtain more benefit from the increased RAM with 4 modules then the largely theoretical performance advantage of using 3 RAM modules. This is especially true for video editing. Forget theoretical benchmarks and max out your RAM.

(Read those articles more carefully rather than just skimming a headline phrase from them - they recommend 4 sticks not 3.)