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    SubjectRe: UDMA 100 / PIIX4 question
    Date
    Jeremy Jackson wrote:

    > Yes this is why I originally replied to the post... but he's not using a PIIXx at
    > all,
    > but the IDE chip on an Intel 815 motherboard. I'm not sure if they use the same
    > driver
    > , but I don't think so.

    I only know i810 systems from experience, but they use a 82801AA which
    is still reported as PIIX4 in /proc/ide/piix (so probably is quite
    similar, apart from supporting UDMA/66). I assumed that might be the
    same for i815.

    > > hdparm speed measurements differ by filesystem (i have no idea why,
    >
    > this is false. They may differ by partition, since different parts (zones) of a

    i know. i found it hard to believe myself, but the numbers are
    consistently lower even on the same partition. i used to have a spare
    partition for things like this (hda6 below), unfortunately i cannot
    repeat the tests right
    now because it is currently in use.

    but if it were a matter of different disk zones, only the buffered disk
    reads should get slower, not the buffer-cache reads.

    > include output of fdisk so we can see partition layout, and results of hdparm on
    > different areas.

    Disk /dev/hda: 255 heads, 63 sectors, 5606 cylinders
    Units = cylinders of 16065 * 512 bytes

    Device Boot Start End Blocks Id System
    /dev/hda1 * 1 255 2048256 6 FAT16
    /dev/hda2 256 5606 42981907+ 5 Extended
    /dev/hda5 256 511 2056288+ 83 Linux
    /dev/hda6 512 767 2056288+ 83 Linux
    /dev/hda7 768 1023 2056288+ 83 Linux
    /dev/hda8 1024 1089 530113+ 82 Linux swap
    /dev/hda9 1090 5606 36282771 83 Linux

    /dev/hda:
    Timing buffer-cache reads: 128 MB in 1.41 seconds = 90.78 MB/sec
    Timing buffered disk reads: 64 MB in 3.04 seconds = 21.05 MB/sec

    /dev/hda1:
    Timing buffer-cache reads: 128 MB in 1.66 seconds = 77.11 MB/sec
    Timing buffered disk reads: 64 MB in 3.51 seconds = 18.23 MB/sec

    /dev/hda5:
    Timing buffer-cache reads: 128 MB in 1.20 seconds =106.67 MB/sec
    Timing buffered disk reads: 64 MB in 2.32 seconds = 27.59 MB/sec

    /dev/hda6:
    Timing buffer-cache reads: 128 MB in 1.20 seconds =106.67 MB/sec
    Timing buffered disk reads: 64 MB in 2.37 seconds = 27.00 MB/sec

    /dev/hda7:
    Timing buffer-cache reads: 128 MB in 1.20 seconds =106.67 MB/sec
    Timing buffered disk reads: 64 MB in 2.33 seconds = 27.47 MB/sec

    /dev/hda8:
    Timing buffer-cache reads: 128 MB in 1.21 seconds =105.79 MB/sec
    Timing buffered disk reads: 64 MB in 2.31 seconds = 27.71 MB/sec

    /dev/hda9:
    Timing buffer-cache reads: 128 MB in 1.21 seconds =105.79 MB/sec
    Timing buffered disk reads: 64 MB in 2.30 seconds = 27.83 MB/sec

    the kernel is 2.4.2ac18 btw. i know its not the most recent, but that
    shouldn't matter. this behaviour has been there for a long time. i am
    not even sure if this was ever any different.

    holger
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