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Apple OSes and IDE DMA Support?

Posted by Cliff on from the they-couldn't-have-overlooked-this-could-they dept.

KFox wishes to get to the core of this particular issue: "I just recently purchased an iBook and I have noticed that even in Jaguar, the system gets choppy from disk I/O. It appears that Mac OS 9 and Mac OS X don't support DMA access for hard drives, even if the drives are initialized in a UDMA mode. Wintel has had support in this area for a long time (since Win95b). Has anyone in the Mac world had any experience with DMA support on hard drives? Is it supported on iBooks? If so, which models?"

1 of 49 comments (clear)

  1. DMA check for your ibook by TwP · · Score: 4, Interesting
    DISCLAIMER: I have not tried this, but I found a webiste that has ...

    Daemon News has a little section on the iBook and DMA. You can see the Darwin boot sequence by holding down the "v" key at startup. Find the section titled "Further Exploration: Das Boot" in the article above and it will tell you how to view the boot messages and other useful tidbits.

    IOATAPICDDrive: Using DMA transfers
    IOCDDrive drive: MATSHITA, CD-ROM CR-175, rev 5AAE [ATAPI].
    IOATAHDDrive: Using DMA transfers
    IOHDDrive drive: , TOSHIBA MK3211MAT, rev J1.03 G [ATA].
    IOHDDrive media: 6354432 blocks, 512 bytes each, write-enabled.


    It appears that this revision-A iBook does indeed have DMA enabled for both the hard drive and the CD-ROM drive.

    This does not help you enable your own DMA, but do a search on Google for enabling DMA on FreeBSD style systems. You might find something useful.