Mac Pro memory source and answers.

Discussion in 'Mac Pro' started by Anonymous Freak, Aug 9, 2006.

  1. Anonymous Freak macrumors 601

    Anonymous Freak

    Joined:
    Dec 12, 2002
    Location:
    Cascadia
    #1
    Alright, I have contacts in Intel's server group (because I used to work there,) which has a few systems similar in design to the mac pro. So I have some answers regarding memory for the Mac Pro. (For source of memory now, see end of this post.)

    First, it uses a new type of memory module called an 'FB-DIMM'. These are standard DDR2 chips on a module that also has a controller chip. This controller chip converts 72-bit-wide ECC DDR2 signals into 10-bit-wide, but much faster, signals. This allows fewer traces per memory channel. This is what allows systems to easily use four channels of memory, when the previous high end was two. This makes memory accesses MUCH faster. This also means that because of the controller chip, the module runs hotter, so they slap on heatsinks. (The other advantage is that FB-DIMMs can contain up to 36 memory chips per module, a higher density than standard DIMMs could 'officially' handle, allowing higher-capacity modules.)

    Another benefit is that these controllers allow more DIMMs per channel. Right now, with conventional DDR/DDR-2, you get a max of 2 DIMMs per channel on high-speed systems, 4 on lower speed. FB-DIMMs support up to 8 DIMMs per channel, at max speeds. And current chipsets have support for up to 6 channels, theoretically at DDR2-800 speeds. (But, a system performs best when memory speed is the same as processor bus speed, so two 667 memory channels per 1333 processor channel makes sense right now.)

    The final major benefit is that since the controller chip is what really talks to the mainboard, one could make newer controller chips that talk to newer, faster memory, without a motherboard/chipset update. So while DDR2-667 is what FB-DIMMs use now, we could see DDR3-1333 FB-DIMMs in the future that are 100% compatible with current systems. (Although current systems probably wouldn't be able to handle all the increased speed.)

    Ah, here's a good explanation from HardwareSecrets.com.

    Second, there *IS* a source for FB-DIMMs, right now. Crucial Technology, the retail arm of memory maker Micron, sells them right now. Their 'Memory Advisor Tool' even has the Mac Pro in its database. From pics taken at WWDC, it appears that Apple is using Micron DIMMs in their systems already, so this is probably your best source right now. (Intel's server group has used Micron as their 'gold standard' of memory for at least a decade now, so it's not really a surprise. When I worked there, we always used Micron memory on our test systems.)

    While Crucial doesn't have any 2 GB modules available yet (which would be needed for the max 16 GB,) they do have 1 GB modules (and 2 GB 'kits' of two 1 GB modules,) for approximately half the cost of Apple. ($343 for the 2 GB kit, which would be $1372 for 8 GB, as opposed to Apple's $300 just to upgrade to 2 GB, or $2500 for 8 GB. You could even then sell your two included 512 MB modules to someone else for a nice bit to help offset the cost of the Micron modules.)

    P.S. No, the Intel server group did not design the Mac Pro. Maybe the workstation group was involved, I can't say for sure, as I don't have any contacts in that group. So no, I can't get you a deal on a Mac Pro; although everyone I know in the server group really wants one.
     
  2. Chaszmyr macrumors 601

    Chaszmyr

    Joined:
    Aug 9, 2002
    #2
    Is there anyone out there that can verify if the RAM from crucial is identical to the RAM Apple is using?
     
  3. Anonymous Freak thread starter macrumors 601

    Anonymous Freak

    Joined:
    Dec 12, 2002
    Location:
    Cascadia
    #3
    Some of the pics around the web (see the front page story,) show them containing memory with Nanya stickers (link, almost all the way down,) but Apple's How to replace Mac Pro memory manual shows Micron memory.
     

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