Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!usc!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!fozzie!stanley From: stanley@phoenix.com (John Stanley) Newsgroups: comp.sys.ibm.pc.misc Subject: Re: Should I connect printer serial or parallel? Message-ID: Date: 21 Jan 91 23:59:17 GMT References: <55304@eerie.acsu.Buffalo.EDU> Organization: Not BIFF At All (NBAA) Lines: 40 v087mxgb@ubvmsa.cc.buffalo.edu (Shawn E Thompson) writes: > In article <6117@spdcc.SPDCC.COM>, jin@spdcc.COM (Jerry Natowitz) writes... > >I have an Epson LQ800 printer that I will connecting to my not yet > >received PC. Is there any performance advantage to using the parallel > > YES. Parallel can run up to 8 (I think) streams of data > in synchronicity, where serial can run one. Parallel does not run 8 streams of data. It runs one. It can carry all 8 bits of the one stream of data at one time, whereas serial presents this one stream of data one bit at a time. The main advantage of parallel is that it is a handshook data path. That means that when the sender puts data on the lines, it says "here it is". THe recipient takes it off the line and then says "thanks I got it." The recipient can also say "don't send me anything right now I can't take it". The path can be faster than serial, since the sender doesn't put each piece of data out for a fixed length of time -- it sends the next piece as soon as the recipient has the last. It can also be slower, if the recipient is slow at acknowledging. Serial data is sent one bit at a time, with each bit being presented for a fixed length of time. It doesn't matter if the recipient can take data faster, you are limited by the baud rate on the serial line. The only advantage you will see when using a character printer is that you can fill its buffer faster, and the system will think printing is finished sooner. If your printer can print 240 cps, you won't actually finish printing any sooner whether you use 2400 baud serial or parallel. But, the faster you fill the buffer to the printer, the faster your computer will be free to do other things. The other advantage to parallel over serial is that parallel has only ONE wiring method, and only ONE handshake system, where serial has X-ON/X-OFF and RTS/CTS and about a dozen different ways to wire a cable. Now, one advantage to serial that parallel does not have is that serial is bi-directional. If you have a fancy new PostScript printer, it likes to send error reports back to the host. It can do this over a serial line.