Path: utzoo!mnetor!uunet!husc6!mailrus!ames!killer!elg From: elg@killer.UUCP (Eric Green) Newsgroups: comp.sys.amiga Subject: Re: Amiga as workstation (serial ports, really) Message-ID: <4031@killer.UUCP> Date: 9 May 88 05:26:23 GMT References: <8805051951.AA26195@cory.Berkeley.EDU> Organization: The Unix(R) Connection, Dallas, Texas Lines: 45 in article <8805051951.AA26195@cory.Berkeley.EDU>, dillon@CORY.BERKELEY.EDU (Matt Dillon) says: > :What, huh?? I've never seen anything shove bits as fast over a serial line > :as you can over a parallel line. Try comparing the time to download fonts > :to LaserJet II on parallel vs. serial (even at 19.2Kbaud) sometime, and see > :if you don't want to keep your parallel port around when you get a laser > :printer. > Ahh hah haa ha.... Man, you haven't seen serial lines. There are > a couple reasons people use serial rather than parallel. When I > design *any* custom communications hardware, I always use serial. > > (1) You can do it with a twisted pair, and only two drivers on either > end. Or at worst three wires (full duplex operation). With > full duplex I usually run data communication synchronously. > (2) You can run the things *fast* ... So fast, in fact, that in > many cases one doesn't even need to check the TxRegister Empty > bit... the bits gets shifted out faster than you can write the > port. > > It isn't my fault idiot manufacturers are still running their > serial ports at 19.2KB. As an aside, I've seen an Amiga shift data out its serial port at 320Kbaud. Wasn't much machine left over for users, though :-). I suspect that the main reason that "idiot manufacturers" still run their serial ports at 19.2Kbaud is because most commercially available (= CHEAP) UARTs are only capable of 19.2Kbaud. For example, the 6551, which is cheap, has low chip count (add a crystal, bus buffers, and ready to go), and is easily interfaced with 68xx/65xx/68K-based machines. I suspect there's an aweful lot of 6502's out there (e.g. I recently discovered that the TVI 910 was 6502-based, when I patched a bug in their firmware for a local university). Higher bitrates seem to require either more expensive chips, or custom chips like in the Amiga.... and, of course, there's always the ULTIMATE in bitrates, fiber-optic Ethernets at 5 megabaud and up. But for a low-cost interface for modems and printers, I suspect that 19.2kbaud is going to hang on for quite a while (at least until 38kbaud equipment becomes more common). -- Eric Lee Green {cuae2,ihnp4}!killer!elg Snail Mail P.O. Box 92191 Lafayette, LA 70509 "Is a dream a lie that don't come true, or is it something worse?"