Archived posting to the Leica Users Group, 2001/04/04

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Subject: RE: [Leica] Re: film scanners
From: "Austin Franklin" <darkroom@ix.netcom.com>
Date: Wed, 4 Apr 2001 04:20:54 -0400

> Just by using a SCSI PC Card I could significantly increase the
> performance of the Nikon LS-2000  (but it's SCSI II and not Ultra).

It shouldn't matter what SCSI it is (SCSI II or Ultra).  It is limited by
how fast the actual scanning happens, and the scanning is far far slower
than the SCSI bus.  The scan takes as long as the scan takes...  What did
you switch from?  I guess you switched from parallel or USB to SCSI?

> It also means that my Iomega Jaz 2 GB is slowed down since it is on the
> same SCSI chain and the Iomega does use Ultra SCSI :-(

Though IOMega does say they support Ultra SCSI for a Jaz drive, but, it
really makes no difference.  The media transfer rate of the Jaz drive is so
far below even SCSI II, that it will make no difference to how fast the data
gets from the Jaz drive to the memory...

The maximum sustained transfer rate for the 2G Jaz is 8.7MB/sec.  Less than
half that of SCSI II...  The only time it does burst, is when reading from
cache, which isn't very often...and especially not for large files.

You don't necessarily slow down the SCSI bus by having slower devices on the
bus.  It's only the data phase that is run at "SCSI II" or "Ultra" rates,
not the negotiation phase.  This means that if you have a SCSI I device, and
an Ultra device, both will operate at their mad data transfer speed, since
the negotiation will be done at the slowest speed, and the negotiation takes
an infinitesimal amount of time.

All this is like "Urban SCSI Myths"...