# Re: scsi command queuing

From: Henning Meier-Geinitz (hmg-ml@gmx.de)
Date: Fri Jun 30 2000 - 11:20:50 PDT

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  Hi,

  On Thu, Jun 29, 2000 at 02:14:25PM +0200, abel deuring wrote:
  > > Same here. I looked at the scanning times when the backend does nothing but
  > > getting data from the scanner and ignoring it. There was no big change in
  > > scanning time (about 5 %). With the original SCSI adapter the Mustek
  > > scanners are about twice as slow as with Windows despite large (4 MB) SCSI
  > > buffers and tweaking the Linux SCSI driver.
  >
  > Which adapter is shipped with the Mustek? And do other adpaters work
  > better?

  DTC-3181 or 53C400A. No interrupt (at least with Linux). The driver
  (g_NCR5380) blocks the whole system while waiting for a request. With some
  tricks (inserting usleeps) the driver is usable but gets slower. With the
  standard 128 MB SCSI buffer size scanning in high resolution is about 10
  times slower than with Windows because of backtracking after each read. With
  larger buffersizes I can go up to 2 times slower than windows.

  With a different SCSI host adapter (Adaptec 2940 or NCR 810 clone) it's
  better and the scan performance is about the same as with Windows in most
  (but not all) situations.

  I haven't checked yet what happens if I reserve a large SCSI buffer and
  enter small (32k or 64k) read requests.

  Ciao,
  Henning

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