SCSI v USB Scanners?

  • Thread starter Thread starter John
  • Start date Start date
David Littlewood said:
That's great; I wish you could share your secret. I have rarely been
able to get two devices to work on the same chain, whatever combination
of terminators/no terminators, permutations of device numbers etc. I
tried. Life is too short to waste on stuff like that...
Click to expand...

Something worth reading (for laughs, if not actual insight) is the
SCSI FAQ where FAQ means "facetiously" answered questions:

http://world.std.com/~dpbsmith/scsifaq.html

The relevant part is, under Types of SCSI:

3. Fast and loose SCSI. Often used in PCs. Has a few small variations
from the official SCSI specification but works quite well as long as
you never install new equipment or change the configuration.

Another relevant part, and one reason SCSI has failed:

In practice, SCSI-2 didn't work either. The industry's response to this
was SCSI-3, which introduced thicker, sturdier, stronger, heavier, and
far more expensive cables. [With 68 pins!]
 
Bill Tuthill said:
David Littlewood said:
That's great; I wish you could share your secret. I have rarely been
able to get two devices to work on the same chain, whatever combination
of terminators/no terminators, permutations of device numbers etc. I
tried. Life is too short to waste on stuff like that...
Click to expand...

Something worth reading (for laughs, if not actual insight) is the
SCSI FAQ where FAQ means "facetiously" answered questions:

http://world.std.com/~dpbsmith/scsifaq.html

The relevant part is, under Types of SCSI:

3. Fast and loose SCSI. Often used in PCs. Has a few small variations
from the official SCSI specification but works quite well as long as
you never install new equipment or change the configuration.

Another relevant part, and one reason SCSI has failed:

In practice, SCSI-2 didn't work either. The industry's response to this
was SCSI-3, which introduced thicker, sturdier, stronger, heavier, and
far more expensive cables. [With 68 pins!]
Click to expand...
Bill, thanks for that, it gave me the best laugh so far this week. It
actually sounds very close to my own experience of SCSI.

David
 
R. P. said:
of the PC's



Firewire is as light on the CPU as SCSI? I had no idea. That's good
to know when trying to decide what kind of external HD backup drive to
get: USB-2 or Firewire.

Rudy
Click to expand...
I have an external firewire hard drive (internal in an enclosure), and
it uses very little CPU while transferring files. I can only imagine
what happens if I use the USB2.0 port instead.
 
David Littlewood said:
That's great; I wish you could share your secret. I have rarely been
able to get two devices to work on the same chain, whatever combination
of terminators/no terminators, permutations of device numbers etc. I
tried.

Life is too short to waste on stuff like that...
Click to expand...

I don't know what my secret is but I'm running Windows XP with SIIG
SCSI card. I'm always plugging things in and out and with very little
trouble. I have a external zip drive, HP Scanjet 5p, Minolta
Elite-2900, and a HP 7450. Really I find SCSI as simple as USB. SCSI
rocks over USB 1.

Wish I could be of more help.
 
David said:
That's great; I wish you could share your secret. I have rarely been
able to get two devices to work on the same chain, whatever combination
of terminators/no terminators, permutations of device numbers etc. I
tried.
Click to expand...

I'm using SCSI devices for ages. I have two CD drives (reader/writer)
and an external SCSI scanner, sometimes an external ZIP or (no longer
used) a streamer attched to the same chain and never had any problems.
on another system there are SCSI drives, SCSI ZIP and SCSI DVD-R. No
problems too.
Neither under Windows, nor Linux or even DOS.

USB, however, is an awful thing, requires LOTS of resources (big,
complicated drivers, huge CPU usage) and, well, the theoretical speed is
- theoretical. Two devices and you might be lost.

Use an USB mouse and an USB scanner at the same time and chances are
you're messing things up.

Well, USB is the cheap solution - in _every_ aspect.

Grossibaer
 
Since I've just been struggling with USB, I think I can contribute a few points.
Hello

A lot of people seem to recommend SCSI connected scanners over USB
ones, but isn't USB faster than SCSI?

Maybe I'm wrong but I thought the speeds for the two standards were as
follows:

USB2 480 Mbps
SCSI-3 Ultra 20 MBps

I thought that even USB 1 was 40 Mbps? So wouldn't that have been
faster than the latest SCSI-3 Ultras speed can muster?

Or perhaps the difference comes with the controllers and the SCSI just
has better controllers and drivers, and the USB takes up too much
resources? Or perhaps the USB can't achieve the top speeds it is
supposed to be capable of, but the SCSI can?

I'm a tad confused on this, but it does seem from what people say in
comp.periphs.scanners that SCSI is faster?

Thanks for any clarification on this

John
Click to expand...

As someone else already pointed out, the USB rates are in bits (Mb).
SCSI is probably in bytes--that's the way you've written it (MB).

USB has a max rate of 12Mb. I've read several sources saying actual
throughput will be much lower, like 2Mb. I'm not sure if USB 2 has
the same ratio of actual/max.

For what it's worth in terms of the usability discussion, I've had no
luck getting a printer to work with USB on Linux, though my USB
scanner worked fine.
 
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