From: "Nicola Bortolotti" <nbsoft AT libero DOT it>
Newsgroups: comp.os.msdos.djgpp
Subject: Commport problems in *two* Win95 dosboxes
Date: Mon, 3 Jan 2000 19:03:41 +0100
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Message-ID: <84qobd$vs7q$1@fu-berlin.de>
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

Hi Everybody,

I was rewriting in DJGPP a fax&voice on demand Clipper application. Normally
*two* copies of this app should run in *two* Windows 95 dos boxes, driving
*two* modems at a time.

With Clipper I've experienced rarely modem buffer underruns, just during the
simultaneous playing of two PCM files (115200 bps DTE-DCE speed, of course).

But with two DJGPP apps running concurrently, the performances become very
worse than Clipper (a P-Code pseudo-compiled language with a freeware add-on
to drive commports!). The underruns make the PCM files pretty unaudible,
severely crackling!

What a surprise! The revenge of the runtime interpreted Clipper code...

It seems like DJGPP apps don't like Windows DosBoxes in background (in
foreground they run fine but one at a time). Including __dpmi_yield() in the
outportb cycle just hangs the execution...

Please note that the commport output is unbuffered in both DJGPP and Clipper
cases. Under DJGPP I've used SVAsync library.

Thanks in advance for any suggestion.


Greetings from Italy

Nicola Bortolotti
nbsoft AT libero DOT it
www.geocities.com/SiliconValley/Station/1269