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From: huilin@hpindda.HP.COM (Hui Lin Lim)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Installation of DECNET DOS on pc's
Message-ID: <4330114@hpindda.HP.COM>
Date: 8 Dec 88 16:14:10 GMT
References: <882@acer.stl.stc.co.uk>
Organization: HP Information Networks, Cupertino, CA
Lines: 49


 gp@stl.stc.co.uk (Gerald Pearse) writes: 
> Our PC hardware consists of a
> 1) TANDON 286 pc
> 2) 3c501 - 3com Ethernet card
> 3) Video Seven VGA card
> 
> After installing DECNET DOS on the PC, when the machine
> is rebooted the machine just hangs. After contacting DEC
> software support I eventually found out that DECNET DOS
> does not work with the VGA cards.
> 
> When I replaced the VGA card with an earlier VIDEO SEVERN
> Deluxe Card (the card that does EGA emulation but NOT VGA
> emulation) DECNET DOS comes up OK. And I can communicate with
> the VMS/VAX OK.
> 
> Question:
> 
> 1) Does anyone know of a work around to get the VGA card working
>    with DECNET DOS. As there must be a difference in the way
>    VIDEO SEVERN guys, have done the VGA card, and the earlier
>    EGA card. Any ideas to the difference between the cards,
>    as I may be able to frig the 3COM card.

I encountered this at my previous job and basically the problem
is that some of the lower level modules that are loaded when
DECNET-DOS is activated use interrupt vectors that were
previously unused but at now used by the VGA.  Unfortunately I
can't remember exactly which ones they are.  I believe the
modules are DLL and the next one down.

I tried patching the code to use another interrupt but found that
it wasn't quite that simple as I couldn't trace all references to
those (2 I think) interrupt vectors.  From what I was told by a
DEC engineer, those bits of code were not written by DEC (their
explanation for why reserved/unused interrupt vectors were used).
It's strange as the vectors involved are declared unused in some
IBM docs and reserved in others.

The easiest way of finding out which vectors are involved is to
use one of the many programs which trace the chaining of TSRs - I
believe that there's one called MAPMEM available from many BBs.


Hui-Lin Lim
ARPA: huilin%hpda@hplabs.hp.com
UUCP: {ucbvax,hplabs}!hpda!huilin
Phone:  (408)447-2835