Additionally, when populating 4 memory slots to gain maximum performance from quad-channel mode, the average improvement over dual-channel is only 3.2%.It's not Apple's fault, but FB-DIMMs absolutely kill memory latency; even running in quad channel mode, the FB-DIMM equipped Mac Pro takes 45% more time to access memory than our DDR2 equipped test bed at the same memory frequency. Things don't get any prettier when we look at memory bandwidth either.
One of our biggest concern about the Mac Pro is that users who don't need 8 memory slots or four cores would be better off if Apple released a single socket Core 2 based Mac tower. The memory performance of FBD on the Intel 5000X chipset is absolutely horrid and there's nothing you can do about it unless you switch entirely to an all serial interface or go back to using regular DDR2 memory.
Can you give some recent examples?quruli said:Workstation/Server memory has always lagged in performance to desktop memory.
I hope so. At this time, this is of no consolation. FB-DIMM prices are high, power dissipation is high, availability is low, and performance is awful.While unfortunate that Intel choose the FBDIMMs, hopefully if Intel decided to continue using this memory the performance will increase.
I think it has to do with the ram being buffered and ECC, I think that whats make it slower, I can't rememeber how the whole thing went but it was something like that.ksz said:Can you give some recent examples?
I hope so. At this time, this is of no consolation. FB-DIMM prices are high, power dissipation is high, availability is low, and performance is awful.
FB-DIMMs are one of the faults. The chipset is another. Though for Xeon workstations, 5000X is one of the better chipsets.Another great article from AnandTech. What concerns me most is the "absolutely horrid" performance of FB-DIMM memory with Intel's 5000X chipset. Conroe (Core 2) with standard DDR2 should have 58% better memory read performance and 29% better write performance.
http://www.tomshardware.com/2004/05/14/two_xeon_cpus_are_better_than_one_intel_p4_extreme_platform/page16.htmlCan you give some recent examples?
Also, lack of hardware RAID suggests that the Mac Pro is not designed for server environments. For that you'll need to attach an external XServe RAID.tobyg said:I store all of my data at home on a RAID 5 setup, and I back it up to tape every other night. Knowing the memory is protected helps me feel better, even at the expense of performance.
No, Apple machines in the past haven't required ECC ram, but most workstation class machines have, in my experience.ksz said:Apple's workstations have never required ECC memory. Non-ECC memory is extremely reliable and is in widespread use. The decision to use FB-DIMMs in the Mac Pro wasn't really a choice. Only Woodcrest chipsets support dual sockets at this time and those chipsets require FB-DIMMs. As mentioned on AnandTech, the fault does not lie with Apple, but with Intel.
Unlike you, I don't welcome the use of high-priced, high-power, but lower performing memory. Unfortunately Apple had no choice, but I suspect this is something that may well change next year.
Also, lack of hardware RAID suggests that the Mac Pro is not designed for server environments. For that you'll need to attach an external XServe RAID.
Simple fact - the machine has been designed and built as a Workstation (and can also serve as a small server - which is why there is an option to have OS X server installed as part of the CTO). Both applications can call for more memory than you would ever install on a desktop games system. FBD memory is the best way to get all those memory slots into a system and hit the kind of price points that Apple is shooting for.The memory performance of the Mac Pro is noticeably better than the PowerMac G5 and competitive with other products in the Mac lineup
The reason Sandra Sisoft 2007 scores higher is because most uses BUFFERED portion of the benchmark. Unbuffered portion of the benchmark is considered to be more realistic portion of the benchmark and scores close to Everest: http://www.anandtech.com/mb/showdoc.aspx?i=2813&p=4("As we have been saying for years, however, the Buffered benchmark usually does not correlate well with real performance in applications on the same computer. For that reason, our memory bandwidth tests have always included an Unbuffered Sandra memory score. The Unbuffered result turns off the buffering schemes, and we have found the results correlate well with real-world performance as we will see shortly.")The numbers at anandtech from the Everest Memory Benchmark seems a bit too low for me. Look at the difference from dual to quad channel memory access. There is noch much difference. But when I look at other Woodcrest reviews there have to be much more bandwidth available.
To all Mac Pro users who can run windows: Please do a Sandra Sisoft 2007 and Everest test and post your memory results.
Maybe there is something wrong with the Apple mainboard or anandtech has been wrong.
Also please tell us if you have user dual or quad channel.
The one of the reasons for FB-DIMM is that the requirements for ECC-DRAM disappears. There's no ECC/non-ECC FB-DIMM. The data integrity features are in all FB-DIMM. Having a non-ECC would mean a regular DDR2 memory. The memory controller may have to change significantly to support that. But the target market Xeons are in means for them, FB-DIMMs are gonna remain.I suspect that a successor to the 5000X may support non-ECC DDR2 memory at the expense of some DIMM slots, or simply realize the full potential of FB-DIMM.
PCs may never need FBD memory, as we are fine with two slots, and capacity of memory per slot increases with advances in technology. Prices are higher for ECC DDR2, but we don't care, as we don't use ECC. Same is for FB-DIMM. I bet for target apps, FB-DIMM is faster than regular DDR2.Im glad they made a push for a mid range mac in the conclusion, yes FBD memory is a issue, and its more expensive and its not as popular, for that you get reliability and more expansion... most of us dont need that, im not worried about it, all I want is to have a fast, quiet, mac that has a bit more expansion than a imac, but doesnt cost as much as the mac pro.
Another thing I read somewhere is FB-DIMM's can read and write memory at the same time, although not at the exact same speeds. I forgot where I read it, but I don't think any existing benchmarks will test for that sort of thing. I know it had something to do with the fact that the memory is buffered so it can actually read and write at the same time.sirnh said:I believe that the memory benchmark used may not tell the whole picture. Most memory benchmarks use a single thread. If you look at the memory architecture for the Woodcrest w/ 5000X Chipset, you see that each processor has a Front Side Bus to its own bank of memory.
When a thread is locked on physical CPU 0, it has a higher latency when retrieving data from the 3rd and 4th channels that are assigned to CPU 1.
I believe a proper test might be to run an instance of the bench mark loop on each CPU, then look at the total memory throughput. It may not give an accurate amount of the real bandwidth of the memory bus, since there will be core contention for the FSB, but I will bet that you will find an increase in performance when channels 3 and 4 can be directly accessed by the cores assigned to them.
This chipset and processor wasn't designed to run a single high-load thread. You can't realize the full potential of the system until you take advantage of ALL of the available resources.
BUT I could be wrong.
That's a good clarification. FBD is not ECC. There is no error correction code in FBD. Instead, it is a form of registered memory, but with a large register array called AMB or Advanced Memory Buffer. This, coupled with the serial path to the FSB, ensures signal integrity and allows the motherboard to contain more DIMM slots without the perils of signal degradation over long circuit paths.DavidC1 said:The one of the reasons for FB-DIMM is that the requirements for ECC-DRAM disappears. There's no ECC/non-ECC FB-DIMM. The data integrity features are in all FB-DIMM. Having a non-ECC would mean a regular DDR2 memory. The memory controller may have to change significantly to support that. But the target market Xeons are in means for them, FB-DIMMs are gonna remain.