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__dpmi_int() or int86() ?

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  __dpmi_int() or int86() ? "Rod Pemberton" <dont_use_email@xnohavenotit.cnm> - 2014-02-15 05:03 -0500
    Re: __dpmi_int() or int86() ? Eli Zaretskii <eliz@gnu.org> - 2014-02-15 16:37 +0200

#1727 — __dpmi_int() or int86() ?

I use __dpmi_int() to call RM interrupts with DJGPP.
So far, I haven't had much use for a PM interrupts.

However, I understand that you can use int86() to call
PM interrupt routines, if installed.  The DPMI host
has installed PM ISRs that will reflect the PM interrupt
to RM.  So, both int86() and __dpmi_int() can be used
to call RM interrupts.  I understand that __dpmi_int()
is generally recommended for this.

But, which is _actually_ faster with CWSDPMI for calling
RM interrupts?  PMODEDJ?  Is it faster to use __dpmi_int()
or to use int86()?  Has anyone actually timed this, in the
past perhaps?  I.e., how does the combined overhead of each
DJGPP call and DPMI portion compare for both?


Rod Pemberton

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#1729

> From: "Rod Pemberton" <dont_use_email@xnohavenotit.cnm>
> Date: Sat, 15 Feb 2014 05:03:46 -0500
> 
> But, which is _actually_ faster with CWSDPMI for calling
> RM interrupts?  PMODEDJ?  Is it faster to use __dpmi_int()
> or to use int86()?  Has anyone actually timed this, in the
> past perhaps?  I.e., how does the combined overhead of each
> DJGPP call and DPMI portion compare for both?

I didn't time this, but I don't think the differences matter much.
Any way you do it, there's a need for two mode switches.  A mode
switch eats up thousands of CPU cycles, which is orders of magnitude
more than any overhead incurred by an extra function call.

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