wcs) (02/26/91)
I'm trying to find out how to connect big laser printers (50-100ppm) to normal computers, in particular to 386/486 boxes running UNIX. For a variety of ugly reasons, I don't want to use Ethernet - I'd really like to use a parallel port. But nobody I've talked to knows how fast a parallel port can go on a typical machine, and nobody's tried it at speeds over about 10ppm. 50-100 ppm is 1-2 pages/second, or typically 40-80 kilobits/second; not much faster than a 38.4 kbps RS-232 port. At least on our machines, and on the parallel port boards anyone knew about, the Centronics driver was simple - the sender toggles a lead when there's a byte to send, and the receiver toggles a lead (causing hardware interrupt) after it reads it. So the hardware guy says "The port can go as fast as the software will handle interrupts." After all, the traditional dot-matrix printer didn't need a whole lot of CPU to feed it data, so there's no hardware assist. Does anybody know how fast the typical 386/33 or 486 box running UNIX can push data out the parallel port? Has anybody tried it? How much CPU does it burn? Unfortunately, I don't have access to a big printer to try it - is there some way to make a parallel port READ data on UNIX? DOS programs like LAPLINK or its equivalents can get fairly high performance, but they're single-tasking programs that can sit there and poll the hardware, rather than sharing a multi-processing machine. Are there any parallel port boards out there with hardware support and/or DMA? It wouldn't take much to do some simple buffering. Thanks; Bill P.S. Sorry about posting this twice; something's having trouble doing cross-posting here, and I'm trying to concentrate followups to one place. -- Pray for peace; Bill # Bill Stewart 908-949-0705 erebus.att.com!wcs AT&T Bell Labs 4M-312 Holmdel NJ # "I can see all Southeast Asia, I can see El Salvador, ..."
debra@wsinis03.info.win.tue.nl (Paul de Bra) (02/26/91)
In article <1991Feb25.220636.23155@cbnewsh.att.com> wcs@cbnewsh.att.com (Bill Stewart 908-949-0705 erebus.att.com!wcs) writes: >I'm trying to find out how to connect big laser printers (50-100ppm) >to normal computers, in particular to 386/486 boxes running UNIX. >For a variety of ugly reasons, I don't want to use Ethernet - >I'd really like to use a parallel port. But nobody I've talked to >knows how fast a parallel port can go on a typical machine, and >nobody's tried it at speeds over about 10ppm. > >50-100 ppm is 1-2 pages/second, or typically 40-80 kilobits/second; >not much faster than a 38.4 kbps RS-232 port. Using the non-interrupt parallel driver (pp) which is public domain one can drive the parallel port as fast as it can go. The maximum speed depends largely on the combination of printer and interface. (there is a big difference between interface boards) I tried several interfaces on my Everex Step 386/25 and a Nec P5 printer, and at 360dpi the best I got was about 3 seconds per 'line', which means about 4kbyte per second. This most certainly will not be enough to keep a fast printer busy, especially not when you are printing bitmaps. Paul. (debra@win.tue.nl, debra@research.att.com)