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    SubjectCheetah vs. UDMA: Bonnie says UDMA is faster! why?


    I almost hate to put this on the linux-kernel list, but the newsgroups
    were of literally no help...

    I have an NCR/Symbios 875 UW scsi controller and Cheetah 4GB hard
    disk. I also have a 3GB UDMA drive (WD 33200). The UDMA is / and
    the Cheetah is /home. This system is primarily a web server.

    I am disappointed in what Bonnie has to say about performance... it
    claims that the UDMA edges out the Cheetah.

    Below are the boot messages: it claims at the end that it is running
    "SLOW WIDE" instead of fast-20... that might be the entire problem. The
    controller comes up and says fast-20 and this is the only device on the
    chain so I can't blame it on an old device sharing the bus.

    My question: is anyone else running this configuration? What can I do
    to get performance up to where it should be? Does the "syncronous
    transfers" section in the kernel config cause this or is it more likely
    to be a jumper setting on the drive?

    I have the drive on the very end of the SCSI cable; could that make a


    -- snip, snip --

    ncr53c8xx: at PCI bus 0, device 10, function 0
    ncr53c8xx: 53c875 detected
    ncr53c875-0: rev=0x03, base=0xe5800000, io_port=0xb800, irq=10
    ncr53c875-0: ID 7, Fast-20, Parity Checking
    ncr53c875-0: on-board RAM at 0xe5000000
    ncr53c875-0: restart (scsi reset).
    ncr53c875-0: copying script fragments into the on-board RAM ...
    scsi0 : ncr53c8xx - revision 2.4a
    scsi : 1 host.
    ncr53c875-0-<0,0>: using tagged command queueing, up to 4 cmds/lun
    Vendor: SEAGATE Model: ST34501W Rev: 0018
    Type: Direct-Access ANSI SCSI revision: 02
    Detected scsi disk sda at scsi0, channel 0, id 0, lun 0
    scsi : detected 1 SCSI disk total.
    ncr53c875-0-<0,0>: SLOW WIDE SCSI 10.0 MB/s (200 ns, offset 15)
    SCSI device sda: hdwr sector= 512 bytes. Sectors= 8887200 [4339 MB] [4.3 GB]


    Kernel config NCR section:

    NCR53C8XX SCSI support (CONFIG_SCSI_NCR53C8XX) [Y/n/?]
    detect and read serial NVRAMs (CONFIG_SCSI_NCR53C8XX_NVRAM_DETECT) [N/y/?]
    enable tagged command queueing (CONFIG_SCSI_NCR53C8XX_TAGGED_QUEUE) [Y/n/?]
    use normal IO (CONFIG_SCSI_NCR53C8XX_IOMAPPED) [N/y/?]
    maximum number of queued commands (CONFIG_SCSI_NCR53C8XX_MAX_TAGS) [4]
    synchronous transfers frequency in MHz (CONFIG_SCSI_NCR53C8XX_SYNC) [5]

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