Re: Mustek ScanExpress 12000SP slow

Nemeth Laszlo (nemeth@qwertynet.hu)
Thu, 03 Jun 1999 17:57:32 +0200

> "Gilbert, Douglas" wrote:
>
> Nemeth,
>
> > Also modified /usr/include/scsi/sg.h to
> > #define SG_SCATTER_SZ (32 * 4096)
> > (this seems to be the new name for SG_BIG_BUFF
> > in kernel 2.2.9 I'm using)
>
> This won't help. It will only make things worse.
> You should leave SG_SCATTER_SZ at 32KB (8 * 4096)
> and try and bump SG_BIG_BUFF up:
>
> #define SG_BIG_BUFF (SG_SCATTER_SZ * 4)

This was the first thing I tried, but SANE (after recompiling) still
transerred 32k blocks only. Then I found this comment below
SG_SCATTER_SZ:

"If scatter-gather not supported by adapter then this value is the
largest data block that can be read/written by a single scsi command."

So it seems the DTC3181 doesn't support scatter-gather. After bumping
the SG_SCATTER_SZ value, SANE transferred 64k blocks (the maximum for my
scanner).
Well, this thing doesn't appear to be a normal SCSI adapter.....

> Then recompile SANE. None of this will probably help
> you ... the DTC3181 is most likely causing the problem.
> Do you have any other SCSI devices (a disk, for
> example)? If so you could use some of my utilities
> to test the throughput of the DTC card.

Unfortunately I have no spare SCSI devices I could test the throughput
with. I guess it'd be very low. In the meantime I found a temporary
solution for speeding things up, with disabling the USLEEP option of the
DTC driver. This is OK, I think, since there are no other devices
attached to the card, so the fact that the scanner doesn't properly
disconnect itself from the bus won't cause any problems.
Now it's still not at the speed that it can do in windoze, but already
acceptable, and doesn't freeze the system while scanning, like in that
other os.

I think I'll pick up a cheap NCR53c810 card for the scanner, and dump
the DTC soon.

> P.S. I would like to email this back to the SANE
> newsgroup but can find no way looking at the archive.
> Do you know the newsgroup (or reflector) address.
> {I don't want to subscribe, my email box is already
> overflowing).

Cc'd to the list, hope you don't mind. I don't know anything about the
news mirror of the list.

Thank you,
Laszlo

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