Dual vs. Quad Channel

The Mac Pro ships with two 512MB FB-DIMMs by default, which means that only two channels are populated. Moving to four FB-DIMMs allows you to have one FB-DIMM in each channel and thus get access to the full 21.3GB/s of bandwidth (in theory). So is there a performance difference between dual and quad channel memory configurations? We ran both configurations with the same amount of memory in all of our tests to find out:

For the most part, there's no benefit to having all four channels populated, but in some rare cases the performance boost can be tremendous. Given that lmbench showed us an increase in memory write speed when going from dual to quad channels, we can assume that the scenarios where we do see a large performance gain are write bandwidth bound.

If you're going to upgrade the memory in your Mac Pro anyways, you might as well stick to four FB-DIMMs as it will give you the best possible combination of latency and bandwidth (as good as you can get with FB-DIMMs that is).

Memory Performance Media Encoding Performance with iTunes and Quicktime
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  • michael2k - Wednesday, August 16, 2006 - link

    1:) Well, according to Anandtech's calculations, it's cheaper to buy a quad CPU Mac than to build one.
    2:) iLife is better than "free crap"
    3:) Macs can run Windows, BSD, Linux, and OS X all at once; PCs cannot
    4:) Drive sleds
    5:) Ram risers
    6:) Quiet case
    7:) 6 SATA connectors
    8:) 4 PCIe slots and 8 monitors
  • retrospooty - Thursday, August 17, 2006 - link

    Yes, in general, good quality components cost more than cheap crap... This is why Acura and Lexus cost more than a Ford, even though they are all built in hte USA. Would you rather get the mobo, memory, HDD, and video card that some kind and caring (cough cough) company landed a mulimillion dollar cotract to buy 10's of thousands, or pick your own?

    What is your point?
  • nexcom - Saturday, November 28, 2009 - link

    yes good and quality also mater aswell ok.
  • michael2k - Thursday, August 17, 2006 - link

    My point was that you got better build quality than the average DIY case:
    You get HDD sleds, cablefree installation, 2 gigE ports, 6 SATA connectors, etc, etc, etc.

    Not everyone has the skill, time, or resources to do their own research, shopping around, and haggling, you know.

    Are you arguing against, similarly, mass produced cars, TVs, homes, fridges, and furniture over DIY solutions?

    Or do you shop at Target and Walmart too?
  • retrospooty - Thursday, August 17, 2006 - link

    MAybe I am dense, but I am still missing your point... Anyhow, Apple's MAC's, or Dell, or any other vendor for that matter are not of high quality parts. The CPU's are great, most of the rest is cheap deal based components. Yes, most people lack the knowledge to build thier own systems, and they buy Dell's, and MAC's and such. All I am saying is that those systems arent at all using all the best high quality/high performance parts.
  • michael2k - Thursday, August 17, 2006 - link

    So I'm asking if you are consistent.

    Do you refuse to buy at Walmart and Target because they sell mass produced furniture, clothing, and household goods because they don't happen to use the highest quality materials? Do you, instead, build your own furniture, make your own clothes, grow your own produce, and make your own electronics?

    I don't see your point, because you haven't proven it, that Macs use "cheap deal based components". The case is definitely not "cheap deal based components" because it is crafted of aluminum ONLY for Apple, and it is quite nonstandard compared to the average PC case. Then there is the Mac motherboard, which as far as I can tell is also unique, being a Xeon EFI based motherboard, crafted singularly for Apple, most likely by Intel itself. The video card, yes, it is cheap, but that saves the user money too, and is no worse than an off the shelf NVIDIA video card.

    Where is your proof that the Mac Pro has cheap, unreliable, components?
  • retrospooty - Friday, August 18, 2006 - link

    you're wearing me out... I give. Long live the MAC, may Apple break thier 10 year rut and finally get more than 3% global marketshare, maybe even 5%. Whoopdeedoo. Yippee skip.

    BTW, Apple's beautiful aluminum cases are a total ripoff (if not an out right purchase)of the Lian Li design. EFI is an average/cheap mobo maker at best (not to say unreliable, just average in function, and performance). They are no DFI, or ASUS, not even close.
  • Maury Markowitz - Friday, August 18, 2006 - link

    You really are trolling...

    > total ripoff of the Lian Li

    Well I've actually used one of these, which I really doubt you can claim, and they're certainly nothing at all like the Apple case. Or are you overheating those two brain cells because both cases happen to use aluminum? I guess, by that brilliant logic, that Apple stole the design of their cases from the Dornier Dr.I from World War I. After all, that used aluminum too.

    For the record, the Lian Li design doesn't show a single one of the features that the Apple industrial design team put into the Mac Pro. They are, quite simply, bog-standard PC cases made of aluminum instead of stamped steel. That's it. For instance, the drives slide in from the front through a removable panel, are fastened into place with tiny little screws, and connected to the mobo with cables. Does this sound like the Mac Pro in any way whatsoever? Well pictures are worth a thousand words:


    > EFI is an average/cheap mobo maker

    Stop! Please, stop! My ribs are aching!

    Hey brainiac, EFI is not a company.

    > They are no DFI, or ASUS, not even close.

    I hope not, considering it's an acronym for a boot standard.

    If this is the basis of your "Apple is cheap" argument, you really are a moron.

  • retrospooty - Friday, August 18, 2006 - link

    Sorry to all, my bad, I read too quickly and I thought the post above was stating that EFI (the company) made Apple's new mobo's.

    Anyhow, I was not saying they are particularily bad, or cheap, I was saying ALL manufacturers use "average" parts in thier systems, including Apple. Aplle may well be at or very near the best of the list of major manufactureres, but its still not like hand picking your own motherboard, ram, v card, HDD etc. In other words, if Apple was an open standard, and any manufacturer could make parts for it, you would see alot of higher quality parts from some of those vendors.

    Any Yes, the case appearance is a TOTAL ripoff of Lian Li. The interior is certianly not, bute the look and feel externally, is identical, right down to the holes.

    Anyhow, I am done on this one, I have riled up enough MAC fanboy anger for now :D LONG LICE MAC, may their marketshare double to a whopping 6% !
  • michael2k - Friday, August 18, 2006 - link

    Right, a total ripoff... you sound like a broken record. Look at Anand's review here:

    It was introduced in April of 2004... almost a full year after Apple introduced their PowerMac G5 in June of 2003. The case design, with the cooling zones, grill face, and inverted motherboard all debuted in an Apple design and then was copied by Lian Li. This has nothing to do with being a fanboy and everything to do with being right.

    You believe Apple ripped off the Lian Li... fine, link the Lian Li that preceeded the PowerMac G5 case!

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