Re: Parallel port sound card?

["Robert George" <george@holmes.cs.nps.navy.mil>]

On Apr 20,  8:24am, John H. Kim wrote:
> Subject: Re:  Parallel port sound card?
> On Thu, 20 Apr 95 08:39:57 -0400 you wrote:
>
> >stop telling me I don't get sound with Doom on a 755C. I am running the
> >original shareware episode on my 755C in a DOS full window with full
> >sound.
>

> 1) I've never gotten Doom's sound (digital or music) working under DOS.

The audio support works fine on the ThinkPad 750/755C's if you have the IBM
 SoundBlaster emulation TSR's running *AND* you are running a program in real-
mode.  For instance, Castle Wolfenstein sounds great.

> 3) Doom's digital audio routines are broken -- it doesn't work on
>    virtually all OS/2 machines, and in some DOS machines.  Has anyone
>    looked into a possible relationship between this and the sound
>    problems Doom has on the TP?  Or are they unrelated?

The sound chip that IBM chose for the 750 and 755C's is register incompatible
with the SoundBlaster OPL-1 chip.  They therefore supplied a real-mode TSR
which intercepts SB interrupt requests and re-routes the call to the IBM SB
emulation routines.

Games like DOOM and Links386, and operating systems like OS/2 run in protected
mode -- they cannot access the real-mode TSR's.  This does not mean that Doom's
audio routines are broken -- they are just incompatible.

If IBM ever re-wrote their SB emulators to run in protected mode, games like
Doom would run fine.

Robert


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| Robert George            |  Army Research Laboratory              |
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