Re: How-to disable irq4 serial ints

[Hufnus <tonyb@thekrnl.sysdev.org>]

On Fri, 10 Jun 2005 19:38:42 +0400
Stas Sergeev <stsp@aknet.ru> wrote:

> Hufnus wrote:
> > Problem is, if the serial device on /dev/ttyS0 is receiving
> > data and generating ints, this serial servicing tsr crashes
> > during its init.
> So finally you did what I suggested,
> and located the broken DOS program
> instead of presuming the bugs in dosemu?

I am afraid that is not exactly true!  It is related
to dosemu not being 100% DOS compatible, when handling these
programs of ours.  Because they have been un-crashable for the
20 years that they have been shipped to customers on vanilla
Dos 3.2 - 6.2

I dont see a fault with Dosemu handling of serial, execept when
we mix it with this Quick Basic/asm Serial I/O TSR combination!

It only crashes Dosemu on a Dosemu restart, if the serial device is
left ON, sending I/O at 1200 baud.

It does not crash when Dosemu starts or when the asm Serial I/O TSR
installs. It crashes on the initial requests between the Quick Basic
Gui trying to start getting serial data events.

Its a hard debug, but we are slowly narrowing THE WHAT is happening,
so it can be resolved, whatever it is...

But it is related to Dosemu 1.2.0 -> 1.3.2, with MsDos 5.0 files,
with our 2 programs, not getting along when Dosemu starts while
serial events are takin place.

The hole issue started when we discovered that: after about 20 or
30 days of continuous running the dosemu clock date/time would get
corrupted. So we started restarting Dosemu about once every 10 days
to get around the corruption.

It is still NOT clear what is at fault,
but it works with real DOS, but that is a
different environment.

Thanks
TonyB

> > Basically I was wondering, if masking the PIC with a 0x04 by
> > doing I/O to port 0x21 would work in dosemu emulation or if there
> > is a better way to do this?
> This *of course* works under dosemu.
> But this may be irrelevant. Because
> unless I am seriously mistaken, the
> DOS doesn't unmask the serial port
> IRQs by default. So if this is the
> problem, you have to search further
> and locate another broken program of
> yours that unmasks the IRQ and forgets
> to mask it back before exit.
> 
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