I'm looking for a basic flatbed Scanner & SCSI card
to use under x86 Linux.
I have some rather FAQish questions, which didn't seem to be
answered by the docs I could find.
The supported devices webpage raised more questions than it answered,
in that a lot of devices are listed as having some kind of support,
but the quality of that support seems to vary a lot.
Not too suprising since most of the people writing the
backends seem to have day jobs.
The kind of devices I'm looking at are Epson GT7000, Agfa 636, Microtek
X6,
and umax 1220S.
The Umax driver seems easily the most complete,
which unfortunately seems to make it the only choice.
Some of my questions concern the SCSI end of things more than the image
end. I've tried to answer my own questions - my answers may be rubbish,
so I'd be grateful for any comments.
I get the impression from reading various SANE docs, and
some of the docs mentioned in the mail-list archives
that scanners (sub-$200 anyway), have rather half-baked
SCSI interfaces.
John.
Q1: Can I operate a scanner on the same SCSI bus as my CD-RW & Zip
drives ? Will any SCSI-II scanner work ?
A1: SCSI-I scanners hold on to the SCSI bus for times you
can measure on a wristwatch. No other device connected to the same
SCSI bus will work while you are scanning. If you do need to use
other SCSI devices while scanning, you could end up with
three or more SCSI busses on your machine: one for the scanner,
one for slow-ish SCSI devices like CDRW, Zip and one for fast SCSI
disk & tape drives.
Seems like SCSI-II scanners should work, but I don't know
if they do. With data rates in the 1 megabyte/s ballpark,
they shouldn't be close to saturating a SCSI-II bus.
If there's a problem, why is it there ?
Or is SCSI I/II a red herring ? I thought SCSI-I devices
were supposed to be able to disconnect/reconnect?
Q2: Are there any well-known SCSI cards that I should particularly
avoid ? What SCSI-card should I get ?
A2: Don't use a scanner on an ultra-scsi bus. Expensive cables &
active termination required. Problematic. Just don't think about
it.
Use a SCSI-II (Fast SCSI) PCI card, with a reasonably inteligent
controller chip (e.g. 53C8xx, 53C9xx, Adaptec etc).
Support for wide SCSI-II is not relevant - neither an advantage
nor a disadvantage.
The above comments apply equally to external CD drives, CDRW, Zip,
and other scsi devices which don't need or support the speed of
SCSI-III (Ultra-SCSI).
Scanners (and CDRW) are often supplied with ancient ISA-bus SCSI
cards.
These cards should be disposed of with due care for the environment,
or mounted on your wall.
Q3: What are the known problems with Linux Kernel SCSI support
with regard to scanners ?
A3: ?generic scsi support broken in 2.2.6-2.2.9 (!)?
?Kernels 2.2.10 & 2.0.37 OK?
?problems with old Advansys drivers ?
?problems with old Tekram drivers ?
?problems with some 53C875 driver versions?
?problems with some 53C810 driver versions?
Q4: Is it required or desirable to configure my Linux kernel
in a non standard way ?
A4: Basically no. You need to configure generic SCSI support
and support for whatever SCSI controller(s) you intend to use.
??Changing SG_BIG_BUF may or may not help??
Further information may be found in the doc for the backend
for your scanner.
Q5: Which scanner manufacturers - if any - provide or fund
SANE (Linux) support ?
A5: ? HP and Umax ? Complete guess.
Q4: Which backends are being actively developed ?
A4: ?Umax, HP, Nikon?
Difficult to tell. Microtek2 maybe. Agfa Snapscan maybe.
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