Separate names with a comma.
Discussion in 'Mac Pro' started by Play4keeps, Jan 24, 2008.
Can some ppl with the new mac pro post Temps of the Ram:
NETLIST VS OWC :Temps
while they are not mine, and don't show netlist vs owc it does have owc on it. http://www.barefeats.com/harper3.html
2 1gb Dimms + 2 2gb Dimms
I found this quote interesting from this article:
"Some of you just want to buy two 2GB FB-DIMMs to add to the two factory 1GB FB-DIMMs for a total of 6GB. That configuration will slow you down. Don't do it. Again, the BEST performance setup is eight matched FB-DIMMs. The second best is four matched FB-DIMMs."
If the type of RAM is the same, why would having different capacities slow down the machine?
Go back and re-read the article...it's a lot to take in all at once, trust me I had to read it a few times to completely understand what was being said.
Basically, to get better speed performance you want to have a minimum of 4 sticks the same exact size, whether it be 4 x 1GB (4GB Total) or 4 x 2GB (8GB total). Not 2x1GB (OEM) plus 2x2GB (6GB total)...
It's because you want an equal amount of ram per core. Quad channel for 4 cores, and octo-channel for 8 core. This will let the ram run faster. Bottom line, you want multiples or 2, 4, or 8 for your ram sticks for optimal performance. With 8 being the best for 8 core and 4 or 8 being equally good for quad core.
if you search you should find some people who have compared, and have found the Netlist runs hotter, that's why i went with OWC, who themselves said the same thing.
That's an interesting article. Particularly for me, since:
1.) I've got a 2.8 GHz early '08 MacPro on order.
2.) Comes with 2 gig RAM.
3.) I want to upgrade to 4 - 6 gig RAM total.
4.) I've never had anything to do with online sales, so trying to unload the original 2 1-gig RAM DIMMS & just go with 2-gig modules from OWC isn't that appealing.
5.) I don't want a 20% drop in memory performance.
6.) I don't want to only use 1-gig DIMMs & limit the MacPro's memory capacity to 8 gigs. Would be great for now, but in 2 years maybe not so much.
So, what happens if I buy 2 1-gig DIMMs to make a 'matching quartet' of sorts, but later in addition buy 2 or 4 2-gig DIMMs? Do I still take a performance hit?
This is entirely inaccurate. FB-DIMM RAM architecture has nothing to do with how many cores the machine has. Please don't spread untruths when you don't know what you're talking about.
OWC 2 x 2 GB in riser B:
Hmmm my B2 Module is typically 12° hotter than it's partner, and both are hotter at all times than the OEM.
There's a picture here, you might have to hit reload to see it as my server is Canadian.
I sort of assume this is a case of someone's first day on the job learning how to apply the thermal paste or something...
Oi! I forgot to mention it's two 2gb OWC chips in the lower RAM carrier.
You have different airflow between the different riser and memory locations.
the 800MHz memory and AMB runs at a higher temp than 667MHz memory/AMB... just like a faster processor runs at a higher temp than a slower one. The AMB is rated to 225F, the memory to 190F.
1GB modules have more devices than 2GB, 4GB have higher density devices than 2GB modules.... Bottom line, more devices generate more heat - devices with more density, more circuit paths inside - also generate more heat. So - yes, a 2GB module will run warmer than a 1GB module.
In a normal server environment that uses JEDEC modules, you have high speed fans that push tons of air across keeping memory temps lower than what happens in the Mac Pro.
In the Mac Pro, you have the large heat spreaders to dissipate heat with higher surface area and a lower rate of air flow... that said, the temps are still higher than you'd have in a server, but WELL within spec.
About matching - each pair is a self contained unit. There is no performance hit for having 1 pair of 1GB from one MFR and another pair that is a different MFR. More performance occurs when two or more pairs are installed due to the multi-point access.. get 256MBit addressing with 2 pairs (one on each riser) vs. 128MBit with a single pair.
1GB vs. 2GB - 1GB modules are all Single Rank. 2GB modules are all Double Rank. The 4GB modules today are all Double Rank - although Apple may in the near future be adding support for Quad Rank (something we'll have to test in terms of performance benefit - but there should be a cost benefit vs. double rank). To be super simple, there is slightly better memory access performance with a Double Rank module vs. a Single Rank - which is why having at least 2 x 4GB Pair (2GB x 2) sets installed gives a benefit over 2 x 2GB Pairs installed or 2GB Pair + 4GB Pair installed. Having said that - the most SIGNIFICANT improvement comes with the adding of ANY 2nd Pair of memory where only a single pair is installed stock.
Hope this info helps.
Larry, thanks for the info. Can you confirm what the optimum temps are for OWC qualified RAM? Tech support emailed me and said it's best to keep my 677MHz 2GB dimms under 73C.
I think most people are trying to put their minds at ease when it comes to RAM temps in the Mac Pro, without having to manually kick up the fans to cool them down.
By the way....what is AMB?
I'll try not to get off topic too much but I have a new MP on order that's coming with 4 x 1GB of RAM.
I was thinking about ordering 2 x 2GB from OWC for a total of 8GB. Is BareFeets and others saying I should just hold off until I can afford 4 x 2GB?
I decided to fill all slots of my coming MP. I ordered another 2 x 1GB so that now I'll have Riser A: 2GB 2GB 1GB 1GB
Riser B: 2GB 2GB 1GB 1GB
It seems to me that two sets of matched pairs filling all 8 slots is the way to go. I chose the extra 2 x 1GB because I didn't want to waste or sell the Apple stock 2 x 1GB.
With OWC Larry's post about MP 800 MHz RAM still being underpriced I decided to act today.
You don't have to buy all 8GB at the same time... you'll get a boost adding 2 x 2GB now... you'll get the same benefit of adding 2 additional 2GB modules now or adding them 6 months from now...
But either way... your Mac Pro will be able to do things a good bit faster with 6GB installed (heck 4GB installed) vs. just 2GB.
AMB = Advanced Memory Buffer. It is essentially a processor that controls the memory access. Each FB-DIMM has its own AMB.
the 667MHz memory is fine up to about 170 F, although unless under heavy loads for extended times in a room with a high ambient temperature (non-air conditioned room near to the 95 F max environmental spec Apple supports for room temp where a Mac Pro is operating) temps typically are in the 110 to 150F range depending on the module size 1GB/2GB/4GD.
the 800MHz a tad warmer as prior noted... and typically should never have to manually turn the fans up or otherwise have auto fan speed increase because of memory temps so long as using modules with the Apple qualified heat spreader utilized. The processors and/or other components may need it... pretty typical too - even with stock min memory to have fans kick when higher end video card is under heavy load.
anyway - 73C = 127F and thats well below any danger zone. Proper spec memory works just as well at 127F as it does at max temp... the max temp being below the point where life span begins to be affected.
and of note - the main hot spot the high temps come from is that AMB.
We have shipped tens of thousands of Mac Pro modules and way back in August of 2006 even did the first heat profiling of modules that was publicly released. Did it mainly cause so many suppliers didn't have the right memory, were telling people that standard JEDEC shield modules were the correct ones (even Crucial initially shipped JEDEC shield vs. Apple qualified spreader modules), and we wanted to show people why that special heat sink was really needed and wasn't just fluff cause XYZ sellers said it wasn't needed.
JEDEC shield modules cool real well in the wind tunnels of the Xeon servers they are specced for. You can't even put Mac Pro spreader equipped into the Xserve and other like servers as the slots are too close as they don't have the room to begin with, but no need cause of the high speed fans blowing through them and out the back. Put those modules in the low flow Mac Pro memory chamber and, well, better let them cool before pulling them out or have gloves on... and the temps those non-Mac Pro modules reach is long term damaging to the devices on the modules as they exceed spec - mainly around the AMB which effectively will cook devices it is near to.
Larry: Nice to see you drop in Just got my 2nd order of 2x2gb RAM from ya, and running faster than ever - thanks
Larry, thanks for the reply. BTW.....your math is off a bit.
73C = 163.4F
That's mainly why I had the original concern with the 677MHz OWC 2GB modules that would consistently hover around 65C-70C (149F-158F) under minimal load, with ambient temps around 21C-24C (70F-76F)
I'm finding that increasing the CPU/Exhaust RPMs up to 600/700rpm helps bring the temps down.
Quick question. I recieved notice today that my 8GB's (4 2GB modules) of RAM I bought from you guys has shipped. Am I better off adding those two pairs to the stock pair that is coming with my Mac Pro (2 1GB modules) for a total of 10 GB's,,, or taking the stock 1GB modules out and just run the 4 2GB modules I'm getting from you guys?
Is 18G going to be worse than 16G?
Okay, if it is recommended to install memory in exponential growth of 2 (2, 4, 8, 16, 32), should I just install my 4 x 4G and leave the previously installed 2g out? Or would I see better performance with the full 18g's?
ProCreator, we seem to have the same question. (Add to the stock, or yank it.)
Leaving the stock 1GB x 2 pair in with additional memory will not reduce performance - more memory is ALWAYS better than less. Even in lower memory configs... we did extensive testing in the Core Duo / Core 2 Duo where you get interleaving with matched pairs. Better performance with 1.25GB than with 1.0gB 512MB x 2.. better to have 3.0GB (1GB + 2GB) than a matched pair of 1GB x 2 by a significant margin.
More memory trumps
A question to OWC larry
I have a question for you, OWC Larry :
my 8-core 2.8 mac pro runs on 4*2Gb qualified OWC memory (800Mhz), as well as the two 1Gb stock ram.
Here are the temperatures of the first two banks of memory (under load, ambiant temperature : 68°F)
160°F and 169°F
(Those are OWC 2Gb sticks)
Are those temperatures acceptable on a long term basis, or should I bump a little the lowest fan settings for cpu/mem ?
What app are you using to get all your temps?