over 4 gig ram concern in audio recording environment

Discussion in 'Windows 64bit' started by Guest, Dec 26, 2006.

  1. Guest

    Guest Guest

    I saw this article while searching for a compatable 1394B I/O card. It was
    relevent to digital cameras locking up XP64 when processing large DMA
    transfers. I am moving to XP64 to use the increased RAM for digital audio
    recording. Can anyone shed light on whether or not this should be a concern?
    I was going to purchase a system with 8 meg of RAM. TIA!

    Mike (mgremlin)
    -----------------
    http://www.ptgrey.com/support/kb/index.asp?a=4&q=253

    The following problem affects 64bit versions of both Windows XP and the
    upcoming release of Vista.

    One of the primary reasons for moving towards 64bit operating systems is to
    increase the maximum amount of memory that can be installed on a system
    beyond the 4GB limit of 32bit machines. Experimentation has revealed that,
    despite the ability to install and configure much larger amounts of memory on
    these machines, attempting to use devices that perform large DMA transfers
    will cause undesirable behavior - primarily system crashes (BSOD, or blue
    screen of death).

    The issue is that machines with at least 4GB of RAM have access to 256 or
    fewer memory map registers. Map registers are required for DMA'ing data into
    the main memory of the computer. One register is required for each memory
    page. Each memory page is 4096 bytes. Thus, in order to DMA a 4096000 byte
    image, 1000 memory map registers would be required.

    Each map register consumes 4K from non-paged memory. The OS will allocate no
    more than a hard coded 256K to a device.

    Based on the current limitations of 64 bit Windows XP, a system with 4GB of
    RAM (256 memory map registers) could theoretically interface with a camera
    that produces 256*4096 = 1048576 byte images (1MB) without any troubles.
    Pending further qualification, it appears as though even this configuration
    will not work in practice on all 64bit platforms - problems have been
    observed with cameras with many different image sizes smaller than 1MB.

    This problem does not happen on 64bit systems with less than 4GB of RAM
    because the OS can address the memory with 32 bit DMAs via a set of "virtual"
    map registers.

    If this behavior is observed, the only short term fix is to reduce the
    amount of memory on the system in question to below 4GB. However, Point Grey
    Research is actively working on a solution to this issue using the
    proprietary FlyCapture software and drivers.
     
    Guest, Dec 26, 2006
    #1
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  2. There are some excellent 64bit audio programs out there, including
    Cakewalk's SONAR. They will take full advantage of >4GB of RAM.
     
    Charlie Russel - MVP, Dec 26, 2006
    #2
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  3. Guest

    Guest Guest

    I already own Sonar. My concern is about where this lockup is coming from.
     
    Guest, Dec 26, 2006
    #3
  4. I haven't seen it, or heard of it. And I highly doubt it.
     
    Charlie Russel - MVP, Dec 27, 2006
    #4
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