YASPP (Yet another serial port problem)

Tom Neff tneff at bfmny0.UU.NET
Fri Dec 29 08:28:02 AEST 1989

In article <12653 at cbnews.ATT.COM> mjs at cbnews.ATT.COM (martin.j.shannon,59112,lc,4nr10,201 580 5757) writes:
>Yeah, well, DOS doesn't use interrupts for the COM devices, so the fact that
>a serial port runs under DOS *DOES* *NOT* mean you have it configured properly
>for UNIX (ISC or any other brand of System V Release 3+ on the '386).

The above quoted poster may be confusing the fact that the standard IBM
PC compatible BIOS serial port service (interrupt 0x14) is polled rather
than interrupt driven, so if you use the BIOS (or the default DOS named
COMn: devices, whose drivers use the BIOS) for your async I/O, you will
not be using interrupts.

But the majority of commercial, public domain and shareware DOS hosted 
communications packages DO NOT use the polled BIOS async service; instead,
they substitute their own buffered, interrupt-driven handlers for the
sake of improved performance. (The necessity of reinventing this particular
wheel in every package ranks as one of the major PC development headaches,
but as Ted Kennedy said, that's all water under the bridge.)

Therefore it's very possible to test a board's interrupt strapping etc.
from DOS.  That's not saying that the UNIX V/386 drivers mightn't be
pickier than a given DOS comm package.
"UNIX should be used          ::   Tom Neff <tneff at bfmny0.UU.NET> or
 as an adjective." -- AT&T   ::    ...uunet!bfmny0!tneff (UUCP only)

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