I did some calcualations, but my scanner never hits the data transfer
rate problem. It seems to get slower at higher resolutions all by
itself.
>
> Well, under Windows95 it usually never did backtracking. When it did,
> it only backed up half the number of times it does with sane. This
> was with the little cheap controller it came with too.
So, they are using a buffer that is twice as large.
> There had got to be a way to get it as fast as under Windows. My scanner
> is backtracking every half inch sometimes. Under Win95 it always moved at
> least a couple of inches before backtracking.
I'm suspecting that a Windows 95 driver may be able to do some tricks
like scatter-gather that are not fully implemented under Linux yet.
If W95 allows scatter-gather, the application allocates a megabyte of
memory, requests a read from the SCSI device, and the scatter/gather
will get the data into the user-pages in the right order.
Under Linux, there is a sg_buffer in kernel space, which is contiguous
so that devices may DMA into that area, and then the data is copied
over to userspace, using the MMU for the pseudo-scatter.
Microsoft operating systems have a vague distinction between
user-space and operating system. Because of this, there are also
some barriers that don't need overcoming under MS software.
Roger.
-- ** R.E.Wolff@BitWizard.nl ** +31-15-2137555 ** http://www.BitWizard.nl/ ** Florida -- A 39 year old construction worker woke this morning when a 109-car freigt train drove over him. According to the police the man was drunk. The man himself claims he slipped while walking the dog. 080897
-- Source code, list archive, and docs: http://www.azstarnet.com/~axplinux/sane/ To unsubscribe: mail -s unsubscribe sane-devel-request@listserv.azstarnet.com