In a message dated 04-18-98, Will Honea said to Don Woodall:
WH>Don Woodall wrote to Will Honea on 04-18-1998
WH>
WH>DW>     From experience, the following chart shows how the BIOS
WH>DW> assigns LPT port numbers to the three main parallel port
WH>DW> addresses.
WH>DW>            3 Ports  2 Ports  1 Port
WH>DW>            present  present  present
WH>DW>            -------  -------  -------
WH>DW>   LPT1       3BC      378      278
WH>DW>   LPT2       378      278
WH>DW>   LPT3       278
WH>DW> 
WH>DW> 
WH>DW>     OS/2 assigns IRQ 7 to LPT1 and IRQ 5 to LPT2.
WH>
WH>Thanks, Don.  Some where I thought I had seen that the
WH>association of 0x278 and IRQ 5 was fixed.  Not real critical,
WH>tho.  BTW, what happens to LPT3?  Does it lose IRQ access,
WH>share it, pretend it isn't there, or what????  What I read
WH>here suggests that the IRQ is tied to the assigned logical
WH>port, not a physical port.   HMMM... simple to handle either
WH>way but a good trivia question. 
WH>
Will
     I may have only answered half of your question.
     You will notice my preface remarks are BIOS BIOS BIOS BIOS.
     Now about the fixed IRQ 5 comment.  Some where along the line
I picked the idea that OS/2  OS/2  OS/2  OS/2 had FIXED the
following IRQ's to the following ports.
     OS/2 IRQ Fixed assignments ?????
          LPT 1   IRQ  7
          LPT 2   IRQ  5
          LPT 3   IRQ 10
The above is assuming that the "/IRQ" switch is applied to the
"print01.sys" device driver.
     A year or more ago I was getting into this with Denis Tonn at
a point in time when he was going to be spending a week at Austin.
My computer crashed for a week or something and he and I never did
finish the thread.
     What I would like to see IBM do is to write new printer
device drivers with switches similar to the serial port device
drivers.
    "basedev=print01.sys (1,3BC,P,S)(2,378,11,B) (3,278,11,C)
(4,178,15,P).
  (LPT#,Address,Poll/IRQ,Port Type)
   Port Type  S = Standard 4 bit parallel port
              B = Bidirectional parallel port
              C = ECP parallel port
              P = EPP parallel port
    Any other ideas anyone?
Don Woodall
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 * MR/2 * Paul Harvey fans always have a good day
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