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|  Does anyone have experience with connecting a ps printer to SGI
|  boxes via the SCSI {1,2} bus ?
|  
|  I have a zippy Xante ps printer. It is quite fast, and I have
|  it connected via a centronics port. I have a breakout box on the
|  line, and I see lots of handshake activity. I think that the
|  printer is out pacing the parallel port on large bitmap images.
|  The printer ready line is can be trapped with no data on the data lines.

You don't say what kind of SGI system it is.  If it is a 30,35, or Indigo,
the parallel port defaults to about 200KB/sec (most printers only seem
to go about 60-70, and we wanted to be conservative).  By running
a small program on the port, you can do an ioctl that will take it up
to 500KB/sec, and still be within the psuedo spec.  You can go even
further, and run up to 1.5 MB/sec, if the printer handles it.

|  This wonderprinter has a SCSI port, and is designed for direct connection
|  to Apple machines. 

Usually the SCSI port is intended for a disk drive for fonts, although
there are a few SCSI printers that take data through the SCSI port
(Kodak 7700 is one we support, and the Laserwriter 1 had a twin that
was designed for printing bitmaps, with no PS interpreter; there is
a sample program in 4Dgifts/examples/devices/devscsi to drive that
printer).

|  Any insight about connecting this to a IRIS ? 
|  
|  What is the max throughput on the parallel lines ?

See above for Indigo class.  For the 20 and 25, it was around
250KB/sec, as I recall, and the IKON vme board was somewhere around
100-200, but I'm really hazy on that.

|  What is the bottleneck in getting data out a parallel line ?

Almost always the printer.

|  The CPU wait line shows lots of physical io waiting, like the
|  whole CPU wait bar is light blue (whatever that means!).

It just means that while sitting in the idle loop, there were
processes that would be runnable if they weren't waiting for i/o
to complete.

|  What is the throughput on the SCSI 1 or SCSI2 bus ? What are the
|  bottlenecks there ?

All kinds of variation here; I'd need to know what machine and/or i/o
board you have (hinv output).  Again, it is usually target device
limited.

|  Would it pay to write/debug a SCSI driver for this beast ? Is there 
|  lp scripts that talk/listen to the SCSI port ? What are the
|  issues to connect a program to a SCSI port ? Kernel drivers ?
|  I don't know if the printer will try to converse with the host
|  via the SCSI port.

You would almost certainly use the pass through SCSI driver (devscsi,
aka 'man ds dslib').  That is what we use for scanners and printers
on the SCSI bus..

Let no one tell me that silence gives consent,  |   Dave Olson
because whoever is silent dissents.             |   Silicon Graphics, Inc.
    Maria Isabel Barreno                        |   olson@sgi.com