Does XP IDE inbox driver check decode range on BAR4 to determine DMA support or not? RRS feed

  • Question

  • Hi all:

    We have an SATA controller with 32 bit decode range on bus master which BAR4[4:0] are Read only.

    We found that this will cause XP inbox driver down to PIO mode rather than DMA.

    We can see a write to BAR4 with value 0xffffffff and another read from BAR4 on PCI analysis machine.

    The return value is 0x0000fff1 for 16 bit decode and 0x0000ffe1 for 32 bit decode.

    So inbox driver does check the decode range of bus master and determines not to use DMA since the decode range is unexpected?

    Thanks a lot! 


    Monday, February 22, 2016 9:32 AM

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