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SubjectDMA questions
Hoi,
Some questions about drives, and DMA, (with kernel 2.0.35 +
Jumbo-2.0.35-9.patch):

-kernel: ide: Intel 82371 (single FIFO) DMA Bus Mastering IDE
-kernel: Controller on PCI bus 0 function 57
-kernel: ide: timings == c070e377
-kernel: ide0: BM-DMA at 0xffa0-0xffa7
-kernel: ide1: BM-DMA at 0xffa8-0xffaf
-kernel: hda: ST36451A, 6149MB w/448kB Cache, CHS=784/255/63, (U)DMA
-kernel: hdb: WDC AC22100H, 2014MB w/128kB Cache, CHS=1023/64/63ide:
Disabling DMA modes on hdb drive (WDC AC22100H).
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

After noticing that, I poked around in the kernel source and found in
linux/drivers/block/triton.c:

/*
* bad_dma_drives() lists the model names (from "hdparm -i")
* of drives which supposedly support (U)DMA but which are
* known to corrupt data with this interface under Linux.
*/
const char *bad_dma_drives[] = {"WDC AC22100H",
NULL};

When/how does it corrupt data? Might it be because of the firmware
bug documented at http://www.wdc.com/quality/err-rec.html (includes
a pointer to a DOS program that supposedly fixes the problem), or
(could it be|is it) something else? I've have tried enabling DMA
on this drive, and it seems to work okay in both Linux and Win95,
but I'm still nervous (all those 'MASSIVE FILE CORRUPTION' warnings
in the hdparm man page :P ).

-kernel: hdd: CD-ROM CDU311, ATAPI CDROM drive

Can't CD-ROM drives do DMA too?

(Apologies if any of this has been asked before,
or if this is the wrong place to ask)

Thanks,
--
Alamais -> alamais@softhome.net
Don't just do something, stand there and ponder!

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