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    SubjectRe: disk corruptions on "tuned" disks Was: APM killing low-latency performance on BX mainboard
    Date
    On Thu, 11 Nov 1999, Dan Hollis wrote:
    > > thanks, but what is the exact problem source , DMA or unmask IRQ ?
    >
    > DMA
    >
    > > I'm watching DVDs for hours ( DMA enabled) without any lockups.
    >
    > It may be ultra dma only bug. Im not sure. My DVDROM and CDROM both
    > support udma.

    I don't played with UDMA on CDROMS, only simple DMA.
    I don't care about a potential UDMA bug,
    simple DMA solves all latency problems, and the performance
    difference between DMA and UDMA on a CDROM drive is almost
    zero. (since the CDROM is the bottleneck).

    The command I usually use to tune the CDROM is :
    hdparm -u 1 -c 1 -d 1 /dev/hdc

    it is a cheap MASHITA 6x DVD drive:

    [root@localhost benno]# cat /proc/ide/ide1/hdc/settings
    name value min max mode
    ---- ----- --- --- ----
    breada_readahead 4 0 127 rw
    dsc_overlap 0 0 1 rw
    file_readahead 72 0 2097151 rw
    io_32bit 1 0 3 rw
    keepsettings 0 0 1 rw
    max_kb_per_request 122 1 127 rw
    nice1 1 0 1 rw
    pio_mode write-only 0 255 w
    slow 0 0 1 rw
    unmaskirq 1 0 1 rw
    using_dma 1 0 1 rw


    >
    > > But are you sure that every ATAPI CDROM drive on the planet
    > > has this hardware flaw.
    >
    > Its the controller not the CDROM at fault

    are you sured that the BX chipset is flawed ?
    It seems to work well.

    >
    > > I stressed my CDROM drives quite a bit, and was unable to lock up the box.
    >
    > What controller and what drives

    Mainboard Gigabyte GA 6BXD (dual) with BX chipset.

    >
    > > How is this handled my other OSes ?
    >
    > They dont run DMA.

    Wrong: try to dig on deja.com searching articles about
    DVD software playback on windoze:
    for most people it is almost impossible to get skipfree video
    without DMA.


    >
    > > > Promise Ultra66. No DMA on CDROM/DVDs. It just wont work. At all.
    > > PS: why should recent ATAPI CDROM let you set the DMA mode, when they
    > > know that it could lead to problems ?
    >
    > Its the controller not the CDROM at fault

    I was wondering how much % of the controllers are faulty in this respect.

    >
    > -Dan

    Benno.

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