# Re: scsi command queuing

From: Wolfgang Rapp (wolfgang@rapp-informatik.de)
Date: Thu Jun 29 2000 - 11:58:58 PDT

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  Oliver Rauch schrieb:

  > if I do not send the image data from the reader_process to the main process
  > (only send read commands to the scsi bus) the scanning speed is not increased.
  > So I also think it is a problem between sanei_scsi, the sg driver and the kernel
  > lowlevel scsi driver. In sanei_scsi there also is a not really necessary memcpy
  > command but I do not think that this command does make the problem.
  >
  > A bit strange is that it does not make any differences if I use 32 KB or 256KB
  > for the read command buffer (The scanner has 256KB internal image data).
  >
  >

  Moin Oliver
  Yes this shows that the scan commands must be send very fast to have no
  stops - because the firmare of the scanners have the same quality as the
  system this hardware is designed to work with ->GatesWare.

  On my old UW driver I use maximum 16K data blocks and no stops with Scanmaker II
  on a 60 Mz Pentium up to 300 dpi 24 bit A4 scans.
  BTW it seems to make problems in DMA transfer if the buffer goes over DMA
  bounderies
  depending on the ugly PC hardware design. So what do the low level drivers with a
  256KB buffer.

  Bye Wolfgang

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