
    

    DMAconf ArcApp Readme 
    1 October 1998

    This program allows system managers to modify the DMA Mode settings
    on Alpha systems which use ARC firmware.  Details on DMA Mode
    settings appear below.  

    To use this program:

        1. Format a floppy disk and copy DMAconf.EXE to the root directory.

        2. Boot into the ARC menu and select "Run a Program."

        3. At the prompt, enter A:DMACONF <enter>

        4. Follow the on-screen instructions.

           
    Enhanced PCI DMA Mode Support

        PCI Master DMA-Window Mode configuration support has been added
        for platforms that support PCI Scatter-Gather DMA. This new
        Advanced CMOS feature allows you to control the DMA resources
        allocated under Windows NT 4.0 for the PCI Master Scatter-Gather
        DMA Window.

        To use the enhanced DMA functionality, your system must have
        Windows NT 4.0 with OEM HAL Revision D or later installed. You
        can avoid installing the updated HAL file by installing
        Windows NT 4.0 Service Pack 4 when it becomes available. 

        Supported DMA modes:

            - Legacy Mode -- use the legacy (original) settings with
              fixed window base and size.  This mode may be required for
              certain non-compliant PCI devices.  This setting causes
              DMA to run as it did in older (legacy) HAL versions.

            - Dynamic Mode -- Dynamically size the Master DMA-window
              proportional to the amount of physical memory present in
              the system.  Relocate the DMA-window base address to a
              location compatible with the system IO address space. 
              This DMA mode is the default and recommended setting.

            - Maximum Mode -- Select the maximum size, 512 MB, for the
              Master DMA-window. Relocate the DMA-window base address to
              a location compatible with the system IO address space. 
              This mode may be required for large PCI device
              configurations.

    This program is not needed for systems with AlphaBIOS.  On AlphaBIOS
    systems, the DMA Modes may be set by selecting CMOS settings, then
    Advanced Settings, in the AlphaBIOS interface.  
