From: Charles Sandmann <sandmann AT clio DOT rice DOT edu>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Is PMODE/DJ Free Software?
Date: Sat, 29 Jun 2002 22:21:37 CDT
Organization: Rice University, Houston TX
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> > "It may be used or distributed in any manner you wish, as long as you do 
> > not try to sell an extender based on PMODE."

>   I think the intention of this is to prohibit anyone from making 
> commercial, closed source derivatives, but it also takes away the right to 
> sell (modified) copies, which is part of the definition of free software 
> (by FSF). There are free software licenses that accomplish the first 
> effect without the second one. Of course, he who writes the code gets to 
> choose the license.

The original author had this restriction and it was included in PMODE/DJ.

The intent is not to prevent you from distributing modified binaries 
including this code.  The intent is to prevent you from selling an EXTENDER
based on PMODE.  You are not selling an EXTENDER, so you are not restricted.
(The DPMI provider in PMODE/DJ does not include any extender services.  
The definition of extender is included in the DPMI 0.9 specification).
The requirement above is less restrictive than the GPL - it says nothing
about providing source (but you do have to provide credits where it
originated).

>   Is there any difference in IRQ handling performance between CWSDPR0 
> and PMODE/DJ when one uses only protected mode interrupt service routines?

PMODE/DJ is faster, yes.

>   1541EMU uses the LPT port IRQ for detecting changes on the Commodore 
> serial bus /ATN signal state. Some Commodore 64 fastloaders use this 
> signal as a bit clock and currently the interrupt handling overhead 
> causes the emulation to occasionally fall behind enough to make it 
> incompatible with such fastloaders. It seems to me that this can only be 
> solved by using the Automatic EOI mode of PIC, because the timing is 
> critical all the way down to single digit microsecond range.

Try PMODE/DJ then - it's definitely faster.