Hi.

>
> At 3/10/98 03:52 AM , you wrote:
> >        Hi.
> >        No, it's more simple. As usual, in bios the on mobo lpt port can be
> >programmed to be decoded as 3BC+ (lpt1), 378+ (lpt2) and 278+ (lpt3), the
> >usual addresses of lpt's from PC's day one.
>
> A bit of confusion about what is Parallel Printer port 1 maybe?
>
> The standard IO address of 3BC+ is for the parallel printer port on a
> Monochrome Adapter card.  The "Printer Port" LPT1 has standard 378+ IO
> address.
>
> True, the standards for "first" printer port has 3BC+, but the standard for
> LPT1 is 378+.
> >
>
> Doug Simmons

        Believe me, it is not quite this way: if you have lpt ports 3BC+ and
378+, they will be LPT1 and LPT2. There is no "standard 378+ for LPT1".
        What happens is that the bios, while checking hardware, scans for
lpt ports at 3BC, 378 and 278 IN THAT ORDER. (So it may happen that if you
have only 278+ it will be LPT1 for the operating system later!) The results of
the scan are left in addresses 0040:0008+. In that sense, LPT1=3BC+, LPT2=378+
and LPT3=278+ is an absolute hardware convention. Another absolute hardware
convention is COM1=3F8+, COM2=2F8+, COM3=3E8+ and COM4=2E8+, although a COM
at 338+ was around for a while, but since it needed a change on more than
one address bit from COM1, it was forgotten. For some DOS COM programs,
COM1 is the first COM found at 40:0+, so it could be that COM1=2E8+!!!
        Then, comes the operating system, which will scan 40:8+, and assigns
its LPTx. If at 40:8 it finds 78 02, you will see LPT1=278 (W95, etc, case).
So the sense of LPT1, COM1, LPT2, COM2, etc, from the os view is first,
second, etc, device found (well, not quite true: I think to remember that
W95 assigns COMs as to the absolute hardware convention). What happens is
that since monochrome cards have been forgotten, 3BC+ presence is a very
rare ocurrence, and 378+ presence is dominant, so 378+ appears as LPT1.
        There remains the DOS concept of "prn": it is LPT1, which by above can
be 3BC, 378 or 278.
        BTW, this email comes from a machine with LPT1, LPT2 and LPT3 at the
conventional addresses. At LPT1 I have a null printer cable to another PC;
at LPT2 I have a zip/printer. A problem comes with DOS EDIT program: it prints
fixed way to LPT1, so for me is useless. A useless and ugly solution is
swap LPT1<>LPT2 at 40:8+; a complicated solution is rename EDIT and build
an EDIT program which calls previous EDIT reassigning DOS printer handle.
It doesn't pay to do this; anyone knows another solution?

************************************
Javier Vizcaino. Ability Electronics. [log in to unmask]

Starting point:        (-1)^(-1) = -1
Applying logarithms: (-1)*ln(-1) = ln(-1)
Since ln(-1) <> 0, dividing:  -1 = 1
     (ln(-1) is complex, but exists)