Apple's Mac Pro - A True PowerMac Successorby Anand Lal Shimpi on August 16, 2006 12:27 PM EST
- Posted in
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).
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rockinphotog - Saturday, August 19, 2006 - linkAS a matter of fact, I often use my apple keyboard for my digital camera, printer, syncing my treo and even my wacom tablet.
aaronlyon - Friday, August 18, 2006 - linkIn next week's article, please evaluate Parallels Workstation for running Windows apps simultaneously with Mac OS. If this works smoothly, why not use Windows versions of Adobe Photoshop and Illustrator? That would be a good solution while waiting for Universal Binary updates.
Zebo - Friday, August 18, 2006 - linkGreat pics and article Anand.
What a deal for such a clean system. They don't build PCs that pretty and this is the best yet from Apple's industrial design squad. I definity want one but don't need four cores.
Can I run Windows fully with this machine? Or maybe I should wait until a single processor (dual core) version comes. If Apple sells $1500 Conroe boxes and it ran windows they counld'nt keep them in stock.
plinden - Friday, August 18, 2006 - link
There's an issue with the speed of SATA hard drives, as Anand mentions here: http://www.anandtech.com/weblog/default.aspx#287">http://www.anandtech.com/weblog/default.aspx#287
It will probably be fixed eventually but if you're relying on this to run Windows, you should wait.
FutureMedia - Thursday, August 17, 2006 - linkYou are not comparing the Quad G5 Rear Ports to the Mac Pro Rear Ports. Quad G5 has 3 USB 2 ports as well as 2 Gigabyte Ethernet ports just like the Mac Pro. IE the Quad G5 rear set of ports is IDENTICAL to the Mac Pro rear set - just laid out differently. Only the front adds a fifth USB 2 and second FW800 port not on the Quad G5 which is the same layout as what you show from OLDER not last generation October 2005 PowerMac G5s.
Moreover I was looking forward to a Quad G5 comparison with the 2GHz and 2.66 GHz Mac Pros. That is what I want to know. Especially Is even the 2GHz Mac Pro faster than the Quad G5? Is the problem that you don't have a Quad G5 in house to compare it to? I am so bummed out that you didn't compare Mac Pro two bottom speeds with the Quad G5. Please can you do it after next week? I would really appreciate it. Thanks.
PhilG5 - Friday, August 18, 2006 - linkThank you so much for pointing that out! In fact, Anandtech uses mid-2004 PowerMac G5 (still using AGP graphics and DDR-400 memory!) and doesn't take into account the whole "late 2005" series (which first supported DDR2, PCI-E and had the "Antares" PPC970 core). If you look at Barefeats benchmark results ( http://barefeats.com/quad06.html">http://barefeats.com/quad06.html ) the Quad G5 still seems to be pretty much competitive with the new Mac Pros.
Anand Lal Shimpi - Friday, August 18, 2006 - linkWe did not have a Quad G5 on hand, however the performance results woult not have been that different. The benchmarks that show little or no scaling between the Dual and Quad Mac Pros would show the same scaling between dual and quad G5s (which were most of the benchmarks). None of our tests were GPU bound, so difference in graphics interfaces should also minimally impact performance. The only real variable that could have changed things is DDR2, however seeing as how none of the DDR-DDR2 transitions we've seen on the PC side have done anything for performance, hopes aren't too high for a tremendous impact on G5 performance.
Konq - Thursday, August 17, 2006 - linkAnand - I think something is wrong with the 2 vs. 4 core Xcode test. As with gcc, you can tell it to compile with as many threads as you like. This will compile 4 source files at the same time for instance on 4 cores (multitasking). Perhaps the code was too small to really see a difference, or the environment was not set right?
Konq - Saturday, August 19, 2006 - linkOK, now another interesting 4-core note: MacWorld did a test with iTunes and a quad core, 2.5 Ghz G5 beat a dual-core, 2.7 Ghz G5 system when converting 45 minutes of AAC files to mp3. Maybe this was due to having multiple files to work on? AAC->mp3 vs. Wave->mp3?
One thing I am interested in now: An article that covers how to get the most out of 4-core systems. Which software benefits and how. Since 4-core processors are coming out soon, this will be needed in purchasing decisions.
Konq - Friday, August 18, 2006 - linkI verified on the Apple Xcode users list that Xcode can indeed take advantage of every core. You might want to modify the test you do and configuration if needed.
Great article btw. I enjoy reading reviews from you that can be counted on for true pro's and con's instead of overly rosey approach from fan sites.
In spite of "horrid memory system", it sounds like the system kicks butt! One is in my future...