LaserWriter II baud rate question

[Daniel R Lance]

In article <1492 at auspex.auspex.com> auspex!guy at uunet.uu.net (Guy Harris) writes:
>
>The SunOS 4.0 documentation does indicate that 38.4KB is supported on the
>CPU serial ports and on ALM-2 ports (no ALM-1/Systech/MTI ports, the
>serial port chip there doesn't support 38.4).  This means "the hardware
>can be run up to that speed"; you can probably find circumstances that
>choke it when running 38.4KB input (as with lots of other boxes), and I
>don't know if it'll run full-tilt 38.4KB on output.

I have had my LaserWriterIINTX running reliably on /dev/ttya of a 3/260,
OS 4.0.1, at 38,400 baud for the last week.  It's easy to do:

1) Stop the line printer queue.

2)  Send the following PostScript code to the printer.  (using cat or
kermit).  This is documented in the LaserWriter IINTX manual from Apple.

--cut here--
statusdict begin 25 sccbatch exch pop
0 eq {stop} if
serverdict begin 0 exitserver
statusdict begin 25 38400 64 setsccbatch
--cut here--

3) Change the entry in /etc/termcap to read :br#38400:

4) Kill -HUP the lpd process.

5) Restart the line printer queue.

I timed some large jobs and saw an effective throughput of about 16,000
baud when printing 1K x 1K black and white rasterfiles;  the printer's
PostScript interpreter is not be able to handle data at 38,400 baud in all
cases.  However, I have noted that normal text-based printing jobs run
significantly faster at 38400 baud than at 9600 baud.  At the higher baud
rate the speed of the print engine is more likely to limit overall
printing speed.

If you can't use 38,400 baud due to cabling cosiderations,  you can use
the above procedure to change your LaserWriter's speed to 19,200 baud,
which will still afford a significant performance improvement.

I haven't tried this with other printers, so I can't vouch that it works
with older LaserWriters or other PostScript printers.  However, a little
poking around in your printer's manual should point you in the right
direction.

--drl
Daniel R. Lance / Federal Systems Division, Eastman Kodak Company
drl at kodak.com / ..!rochester!kodak!lance