Return or exchange such memory immediately, and be sure to run a stress test as described in Testing Memory for Reliability. Theoretical technical discussions [ 1 ], [ 2 ], [ 3 ] about memory bandwidth transfer speed are of little practical value, though they do establish general performance expectations. For many programs, memory bandwidth will have little or no effect on performance, but for some programs the impact can be significant.
Mac Pro (Mid 2012 and earlier): How to remove or install memory
Measured results for specific programs are most persuasive, since all that matters is actual performance of programs you actually use. I tested the speed of various combinations. That could mean a significant performance gain for programs that use large amount of memory, like Photoshop. Dual-rank modules offer slightly more performance than single-rank modules.
Observe that four dual rank modules provide twice the bandwidth of two single-rank modules. Recommendations —. There are 8 memory slots.
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So there can be 2, 4, 6 or 8 modules installed. The riser boards are labeled as to which slot is which. The performance of any specific program might or might not benefit from the optimal configuration, but some programs certainly will.
Bear in mind that paying for a faster CPU eg 3. The claim is that filling all 8 memory slots will in theory reduce memory performance over using just 4 slots due to the nature of the serial data transfer in an FB-DIMM—increased latency of nanoseconds. Furthermore, Photoshop test results show clearly that such theoretical concerns are a waste of time; performance for any challenging task depends on the total amount of memory. For more on the virtues of ECC memory see the Jan 24, diglloyd. Memory becomes less reliable as it heats up.
Nearly all computer designs address this problem the straightforward way—by running fans at obnoxiously loud levels—appropriate for a room full of servers, but inappropriate for a home, or for video or sound processing.
mac pro won't recognize memory sometimes, arrgh | MacRumors Forums
The whisper-quiet design of the Mac Pro precludes the noisy fan solution. Instead, Apple specifies the use of substantial heat sinks on the memory modules, which draw heat away from the memory chips, and allow a relatively low fan speed to keep them at a reliable operating temperature. A problem develops if the memory that is installed in the Mac Pro has inadequate heat sinks; the module will become quite hot and memory errors can begin to occur. This is what occurred with one of four modules I originally purchased from SATech. But ECC memory can correct only 1 bit per byte; errors in two or more bits per byte can be detected but not corrected, and the system would crash.
Note that 2GB modules can be expected to run warmer than MB modules, because they have twice the memory density and twice the chips 4X the capacity. However, as memory chip technology evolves, newer modules even higher capacity ones end up reducing chip count; as of November there are 4GB modules with the same number of chips as once were used on 1GB modules.
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See the Memory installation section earlier in this document. That is precisely what the MemoryTester run-stress-test command does. The MemoryTester utility is a bit program, and can test all available memory. Of the above, one of the SATech standard modules exhibited ECC memory errors and all four were exchanged for the 3 modules—see the March 7, blog entry for details. The remaining modules have never shown ECC errors during stress testing or otherwise.
The program Hardware Monitor was used to observe memory module temperatures as well as ambient temperature and the various fan speeds; these items all have internal temperature sensors which can be read by a program such as Hardware Monitor. Originally extremely expensive, even 16GB is now a fraction of the price of a Mac Pro.
While Apple offers top-quality memory, it comes at a daunting price even as memory prices have dropped. Fortunately, there are lower-priced alternatives which perform as well, and remain reliable under severe operating conditions. Prices as of November are historically low and there is a good chance that memory prices could as much as double later in However, all eight slots will then be full. See How to Configure a Mac Pro. The build quality looks just like the Apple modules, but pricing is far more attractive. OWC has these modules manufactured to their specifications.
See what OWC has to say about how they build and test their memory modules. Users with 2nd-generation 8-core Mac Pros should get MHz memory. The NetList module heat sinks seem somewhat skimpy by comparison, with a narrow point of contact between the heat sinks and the memory chips. This was initially of some concern, but it did not seem to affect their ability to maintain about the same operating temperature as the SATech bi-color memory when tested temperatures are as reported by temperature sensor on the module itself.
These modules are nicely built, with substantial heat sinks. The MB modules are single- rank , and slightly lower in performance than dual rank modules, even when used as a group of four. These modules have inadequate heat sinks that developed ECC memory errors when stress-tested. These modules are not appropriate for the Mac Pro, and were designed for high airflow servers. These modules have heat sinks that are even more substantial than those on the Apple modules. Exactly identical to modules you would buy From Apple both in spec and heat sink used.
This what we will sell from now on when anyone orders Factory Approved Memory. Excellent alternatives to Apple-supplied memory are available at far lower cost times less expensive than Apple. The bottom line is that in 19 months of heavy use of my Mac Pro, I've had zero trouble using alternative memory. Get high quality memory from a 3rd-party vendor, such as OWC , and save a bundle! Interested in photography?
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What everyone should know about Mac Pro Memory Upgrades. Display info: Thank you for purchasing through links and ads on this site. Upgrade the memory of your Mac mini up to 64GB. Top deals pages Anyway, I guess I'm looking at a few different parts. You were in section 5. It says: Figure depicts the next two positions where DIMMs may be added. These positions are depicted in dark gray.
The two upgrade positions are Branch 0, Slot 1 and Branch 1, Slot 0. Of these Branch 1, Slot 0 is the preferred upgrade because it allows both branches to operate independently and simultaneously. While it is possible to completely populate one branch before populating the second branch, it is not desirable to do so from a performance standpoint. If it were the latter, Intel probably would have stated it more clearly.
mac pro won't recognize memory... sometimes, arrgh
Section 4. Section 3. I don't understand all of this section, but if I can go out on a shaky limb here, it says: If the processor-physical address falls in the range defined by an MIR, the 'way' fields in that MIR defines branch participation in the interleave.
The way-sensitive address bit is A. There's one set of these registers per branch in Device 21 for Branch 0 and Device 22 for Branch 1 , and there's no mention of keeping them in sync between the two branches, so I assume they can be configured independently. Which also supports my theory. Finally, this diagram gets linked here occasionally, and you can see that the first configuration I described in my earlier post doesn't appear there, while the second configuration is 8C. Yeah, and that's what I'd go with. Just because Intel's documentation says that the memory controller has an enhanced 2 DIMM mode doesn't mean Apple supports it, for instance.
Originally posted by NuVector: They do. Well, since there are four channels altogether, four DIMMs is always faster than two, so there's no reason to want to try this mode. Originally posted by daveIT: Recently upgraded to 13GB and read some Apple docs and settled with this config. Any opinions?
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Mac-Pro first gen "dual channel" memory question 16 posts. Jump to: May 9, Posts: Tue Dec 30, Zaskar " Nomad Registered: Dec 26, Posts: Seattle, WA Registered: Nov 30, Posts: Wed Dec 31, Alan H. Ars Tribunus Militum Registered: Aug 7, Posts: Fri Jan 02, Jul 2, Posts: Fri Jan 02, 1: Ch0ke Registered: Sep 26, Posts: Fri Jan 02, 3: The place of argent brooks Registered: Dec 22, Posts: Sat Jan 03, 1: