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Received: by minnie.vk1xwt.ampr.org with NNTP id AA1276 ; Tue, 23 Feb 93 14:33:21 EST Path: sserve!manuel.anu.edu.au!munnari.oz.au!spool.mu.edu!howland.reston.ans.net!zaphod.mps.ohio-state.edu!swrinde!emory!sol.ctr.columbia.edu!gondor.sdsu.edu!network.ucsd.edu!sdcc12!icogsci1!cg18fbi From: cg18fbi@icogsci1.ucsd.edu (Richard Dante) Newsgroups: comp.unix.bsd Subject: Re: I need a /dev/com3 !!! Message-ID: <45043@sdcc12.ucsd.edu> Date: 15 Feb 93 11:41:02 GMT References: <1993Feb8.170954.25245@vlsi.polymtl.ca> <1993Feb12.055229.3670@ucsu.Colorado.EDU> Sender: news@sdcc12.ucsd.edu Organization: University of California, San Diego Lines: 55 Nntp-Posting-Host: icogsci1.ucsd.edu In article <1993Feb12.055229.3670@ucsu.Colorado.EDU> galbrait@rintintin.Colorado.EDU (GALBRAITH JOHN) writes: > >In article <1993Feb8.170954.25245@vlsi.polymtl.ca> you write: >> >> I just want to know if it is possible to have a third >>serial communication port. And what it has to be done to have one. >> > >I did it. The INSTALL.NOTES says that only com1 and com2 are supported, >but I think the problem is sharing the interrupts. In dos, com3 shares >INT4 with com1. So, set up your com3 for INT5. (If you have two >parallel ports this may be a problem.) Not all serial ports support >int5, like my modem. I simple had to cut the land going to the int4 >and solder a short wire from the interrupt jumper to the int5 line on >the ISA bus. Set com3 to the appropriate address and int5 in the kernel >config file. > If you need details, I can send you the bus pinout over email. > >john galbraith I'll add my bit to encourage the less-brave-than-he-who-solders-irqs: Before dinner (V-day), had computer apart to try to disable the damned non-cacheable region (DOS kludge on motherboard). Couldn't. Anyways, girfriend rushed me off to dinner before I could finish things up. Anyways, when we got home, my girlfriend passed out on the couch, and me, not being in a very romantic mood (I think a study in open PC cases and unresolved computer tinkering as libido dampeners is in order :() I remembered that my printer driver is interuptless and DOS ignores int 7. So, I messed with jumpers and have: bus mouse (irq 2, no change), internal modem (irq4, com1 no change) , terminal (com2 irq3), and a free serial port (com3 irq5). I disabled the irq going to the printer (was on irq 7 before) and moved my soundblaster from irq 5 to irq 7. Added a com entry to my config, recompiled and viola! Four serial devices (if you count the bus mouse). Printer works fine in DOS, Window, and 386BSD without that irq. Terminal works on both coms. mouse works, everything works. NOW, all you who in theory have more than 2 serial ports (have two cards or whatever), take a look at your serial card manual. My serial card is a piece of crap from Taiwan. It's got 2 serials (16450's), LPT, floppy, IDE, and joystick. The interesting thing is that you can select which com port the two ports go to (1-4 3F8 2F8 3E8 2E8) AND you get to select which irqs (2 3 4 5) for the ports. Not only that, you can jumper a port to force CD, CTS, DSR true and you can even jumper in a null modem so you don't need adapters (card port can be either DTE or DCE). All this with a cheesy taiwanese piece-o-crap from 1989 with the UARTS soldererd in (not only that, the UARTS don't have an ID on them). Now, chances are that those of you who want to go beyond the traditional gimme two irqs and I'll give you your choice o two coms (irq 3,4 com1-4) might have an io card flexible like mine. Take a look. If not, then maybe you are (un)fortunate enough to have an internal modem. If so, it might be switable to irqs 2, 3, 4, or 5 (like mine which is a 16450 emulating (boo!) V32.bis) Rick Dante