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Date: Fri, 11 Jul 2014 14:18:37 -0400
From: "Matt D." <matt AT codespunk DOT com>
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To: djgpp AT delorie DOT com
Subject: Re: Using outportb() with djgpp
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Mateusz,

Here is a link to the Sound Blaster Development Kit. Some of this 
information may be useful:

http://files.mpoli.fi/unpacked/software/misc/players/tbmplay.zip/sbdevkit.doc

See section 8-3 on "Resetting DSP".


Matt D.

On 7/11/2014 4:38 AM, Mateusz Viste wrote:
> Hi,
>
> Thank you all for your kind replies.
>
> The "weird interrupt happening during I/O" sounded sexy enough that I
> had to test it out immediately - I replaced all my inportb() and
> outportb() calls with a function that first call disable(), then do the
> in/out operation, and then call enable() if interrupts were enabled
> before. Unfortunately this doesn't changed my problem - my PC still
> reboots wildly on random i/o operations on the 0x330 port.
>
> Some context: I am trying to play a few notes on my Sound Blaster 64
> (ISA) card using its embedded MPU401 synth controller. It works pretty
> well when compiled in realmode with Turbo C 2.0.1, but then I am having
> a bit of hard time with memory management (64K limit et all), so I
> thought I'd recompile it under DJGPP. And then I experienced those wild
> reboots I was writing before. Interestingly enough, the protected mode
> version works fine on DOSBox.
>
> Of course I am aware that such 'bug report' is good for nothing - I was
> just wondering whether there is some top secret information about doing
> I/O calls from protected mode that I ignored, but I understand now that
> there is nothing specific to do in protected mode (or at least nothing
> much else than in real mode), so I will try to put together some
> minimalistic test program to reproduce the problem on the smallest
> possible example, and then I'll see where it leads me (might get back to
> you then).
>
> Again, thanks for all your prompt replies!
>
> cheers,
> Mateusz
>
>
>
>
> On 07/10/2014 10:20 PM, Mateusz Viste wrote:
>> Hi,
>>
>> I am trying to write to a hardware port from within djgpp, using
>> outportb(). It does work from time to time, but often outportb() will
>> make the whole PC reboot. Specifically I am writing to port 0x330 (to a
>> MPU401 adapter). If using the same code with turbo C, it works
>> perfectly. Hence I am wondering: are there any special "rules" I should
>> be aware of when trying to outportb() from within protected mode?
>>
>> regards,
>> Mateusz
>
>
>