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, ..."
k@hprnd.rose.hp.com (Steve Kao) (03/27/91)
The new HP LaserJet IIIsi comes with a serial/centronics port. The serial port can be configured up to 38.4 Kbps. The centronics port can be configured (ADV FUNCTNS=YES*) to high speed mode (HIGH SPEED=YES*), which can handle up to ~400K bytes per second. A special host driver is required to access this high speed centronics mode. The LaserJet IIIsi is a 17 ppm printer, when connected to a LAN (different I/O card). When using high speed mode centronics, we've been able to get 15ppm with full- page graphics. - Steve Kao