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From: otto@tukki.jyu.fi (Otto J. Makela)
Newsgroups: comp.windows.ms
Subject: Re: Windows Terminal COM port problems (correction!)
Message-ID: <OTTO.90Oct26122121@tukki.jyu.fi>
Date: 26 Oct 90 11:21:21 GMT
References: <407@nwnexus.WA.COM> <DSAMPSON.90Oct25120335@x102a.harris-atd.com>
Sender: news@tukki.jyu.fi (News articles)
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Organization: Turing Police, Criminal AI section
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In-Reply-To: dsampson@x102a.harris-atd.com's message of 25 Oct 90 16:03:35 GMT

In article <DSAMPSON.90Oct25120335@x102a.harris-atd.com>
dsampson@x102a.harris-atd.com (sampson david 58163) writes:
[useful instructions on viewing the BIOS serial port vector with debug:]
   1) On the command line, type debug
   2) When you get the - prompt, type d40:0
   3) The address for COM 1 is F803, but you'll see it displayed in the
   Intel "reverse" notation as 03 F8
   4)  If you see 03 F8  02 F8   00 00   00 00, then your bios doesn't
   recoginize com3 and com4 (it has zeros for its addresses).
   5)  The temp solution (not guaranteed) is to use debug to poke the
   com3 & 4 addresses into that location.  See the new issue of PC Mag V9
   num 19.  One of the help columns in the back talks about this.

I'm afraid you have this backwards.  Make it read:
   3) The address for COM1 is 03F8, but you'll see it displayed
      in the Intel "reverse" notation as F8 03; COM2 is 02F8.
      Standard COM3 should be 03E8 and COM4 02E8.
   4) If the first line of the dump looks like:
      0040:0000  F8 03 F8 02 00 00 00 00-
                 COM1= COM2= COM3= COM4= (corresponds to ports)
      your BIOS doesn't recognize your COM3 and COM4 addresses (the
      addresses for them are zero).  This can be due to either an old
      BIOS or a nonstandard serial card.
   5) You can temporarily fix this if you know that your serial card
      is of the standard type by setting the 40:0 vector addresses
      appropriately (comments follow //, don't type them in):
        a 40:4      // "assemble" data to COM3
        dw 3e8      // set COM3 address to standard
        dw 2e8      // set COM4 also
                    // blank line to get rid of "assemble"
        q           // to finish debug
      You can also give "dw 0" to set the address to zero, if you don't
      have either of these cards.  You can also try hacking this if you
      know that your card generates the appropriate IRQs but is at the
      wrong address, but the results won't probably be as good...
      There are programs available for doing these things automatically,
      look at the anonymous ftp archives at wsmr-simtel20.army.mil
   6) The "proper" solution is to get a BIOS which recognizes COM3/COM4 or
      change to a standard serial card.

PS. I have hacked Windows to use a nonstandard COM port as the mouse port (I
have my MicroS*t Mouse compatible trackball on a non-standard COM).  I've
already once posted instructions, if there is larger interest, I'll post again.
--
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