Mail Archives: djgpp/1997/02/03/07:40:23
| From: | Paul Lay <play AT nortel DOT co DOT uk>
|
| Newsgroups: | comp.os.msdos.djgpp
|
| Subject: | real mode int slower????
|
| Date: | Mon, 03 Feb 1997 11:49:33 +0000
|
| Organization: | Nortel Limited
|
| Lines: | 295
|
| Message-ID: | <32F5D0CD.41C67EA6@nortel.co.uk>
|
| NNTP-Posting-Host: | bhl3s9d.bnr.co.uk
|
| Mime-Version: | 1.0
|
| To: | djgpp AT delorie DOT com
|
| DJ-Gateway: | from newsgroup comp.os.msdos.djgpp
|
I've just turned a protected mode interrupt into a real mode one,
looking
for a performance gain but instead things got worse...
I'm using the timer interrupt (0x08) to read the joystick. What I do is
increase the timer frequency to around 6kHz and install a new isr that
monitors the joystick, building up its x and y positions (at this rate
you
get ranges of 0..9 for both x and y positions). In order to maintain the
time of day and whatever else is done during the normal timer interrupt,
I
periodically chain to the old timer interrupt so that it's still invoked
18.2 times/sec.
I originally did this using protected mode interrupts which worked fine,
but
it seemed slightly more expensive than when previously working in real
mode
under Borland. So I rewrote using real mode interrupts, but this has
proved
significantly more expensive.
Below is my joystick code. Any ideas? Even though I've only installed a
real
mode isr, is it possible that there's still some protected mode isr
processing being done?
Cheers,
Paul.
/***************************************************************************/
/*
Includes
*/
/***************************************************************************/
#include <stdio.h>
#include <dpmi.h>
#include <sys/nearptr.h>
#include <sys/movedata.h>
/***************************************************************************/
/*
Constants
*/
/***************************************************************************/
#define TIMER_VECTOR (0x08)
#define FILL (0x00)
/***************************************************************************/
/* Global
Variables */
/***************************************************************************/
int* joystickX;
int* joystickY;
int* joystickButtons;
/***************************************************************************/
/* Local
Variables */
/***************************************************************************/
static __dpmi_raddr oldVector;
static __dpmi_raddr newVector;
static int joystickIsrSelector;
/***************************************************************************/
/*
*/
/*
joystickIsr
*/
/*
*/
/* This code is copied into dos memory and configured as the real
mode */
/* timer isr. The bytes marked FILL are overwritten during
installation: */
/* the 2 bytes at offset 0x05 are set to the dos memory segment
(where */
/* this code is located), the 4 bytes at offset 0x72 are set to
the */
/* segment:offset of the old real mode timer
isr. */
/*
*/
/***************************************************************************/
static char joystickIsr[] =
{
/* 0000 */ 0x50, /* push ax */
/* 0001 */ 0x52, /* push dx */
/* 0002 */ 0x1E, /* push ds */
/* 0003 */ 0x55, /* push bp */
/* 0004 */ 0xBD, FILL, FILL, /* mov bp,SEGMENT */
/* 0007 */ 0x8E, 0xDD, /* mov ds,bp */
/* 0009 */ 0xFF, 0x06, 0x70, 0x00, /* inc word ptr TIMECOUNT */
/* 000D */ 0x81, 0x3E, /* cmp word ptr TIMECOUNT,0x0155
*/
0x70, 0x00, 0x55, 0x01,
/* 0013 */ 0x75, 0x10, /* jne L1 */
/* 0015 */ 0xC7, 0x06, /* mov word ptr TIMECOUNT,0x0000
*/
0x70, 0x00, 0x00, 0x00,
/* 001B */ 0x9C, /* pushf */
/* 001C */ 0xFF, 0x1E, 0x72, 0x00, /* call dword ptr OLDHANDLER */
/* 0020 */ 0x5D, /* pop bp */
/* 0021 */ 0x1F, /* pop ds */
/* 0022 */ 0x5A, /* pop dx */
/* 0023 */ 0x58, /* pop ax */
/* 0024 */ 0xCF, /* iret */
/* 0025 */ 0xBA, 0x01, 0x02, /* L1: mov dx,0x0201 */
/* 0028 */ 0xEC, /* in al,dx */
/* 0029 */ 0xA8, 0x03, /* test al,0x03 */
/* 002B */ 0x75, 0x2A, /* jne L2 */
/* 002D */ 0xF6, 0xD0, /* not al */
/* 002F */ 0x24, 0x30, /* and al,0x30 */
/* 0031 */ 0xC0, 0xE8, 0x04, /* shr al,0x04 */
/* 0034 */ 0xA2, 0x80, 0x00, /* mov byte ptr JOYBUTTONS,al */
/* 0037 */ 0xA0, 0x76, 0x00, /* mov al,byte ptr XCOUNT */
/* 003A */ 0xA2, 0x78, 0x00, /* mov byte ptr JOYX,al */
/* 003D */ 0xA0, 0x77, 0x00, /* mov al,byte ptr YCOUNT */
/* 0040 */ 0xA2, 0x7C, 0x00, /* mov byte ptr JOYY,al */
/* 0043 */ 0xC6, 0x06, /* mov byte ptr XCOUNT,0x00 */
0x76, 0x00, 0x00,
/* 0048 */ 0xC6, 0x06, /* mov byte ptr YCOUNT,0x00 */
0x77, 0x00, 0x00,
/* 004D */ 0xEE, /* out dx,al */
/* 004E */ 0xB0, 0x20, /* mov al,0x20 */
/* 0050 */ 0xE6, 0x20, /* out 0x20,al */
/* 0052 */ 0x5D, /* pop bp */
/* 0053 */ 0x1F, /* pop ds */
/* 0054 */ 0x5A, /* pop dx */
/* 0055 */ 0x58, /* pop ax */
/* 0056 */ 0xCF, /* iret */
/* 0057 */ 0xA8, 0x01, /* L2: test al,0x01 */
/* 0059 */ 0x74, 0x04, /* je L3 */
/* 005B */ 0xFE, 0x06, 0x76, 0x00, /* inc byte ptr XCOUNT */
/* 005F */ 0xA8, 0x02, /* L3: test al,0x02 */
/* 0061 */ 0x74, 0x04, /* je L4 */
/* 0063 */ 0xFE, 0x06, 0x77, 0x00, /* inc byte ptr YCOUNT */
/* 0067 */ 0xB0, 0x20, /* L4: mov al,0x20 */
/* 0069 */ 0xE6, 0x20, /* out 0x20,al */
/* 006B */ 0x5D, /* pop bp */
/* 006C */ 0x1F, /* pop ds */
/* 006D */ 0x5A, /* pop dx */
/* 006E */ 0x58, /* pop ax */
/* 006F */ 0xCF, /* iret */
/* 0070 */ 0x00, 0x00, /* TIMECOUNT: dc.w 0x0000 */
/* 0072 */ FILL, FILL, /* OLDHANDLER(offset): ds.w 1 */
/* 0074 */ FILL, FILL, /* OLDHANDLER(segment): ds.w 1 */
/* 0076 */ 0x00, /* XCOUNT: dc.b 0x00 */
/* 0077 */ 0x00, /* YCOUNT: dc.b 0x00 */
/* 0078 */ 0x04, 0x00, 0x00, 0x00, /* JOYX: dc.l 0x00000004 */
/* 007C */ 0x04, 0x00, 0x00, 0x00, /* JOYY: dc.l 0x00000004 */
/* 0080 */ 0x00, 0x00, 0x00, 0x00 /* JOYBUTTONS: dc.l 0x00000000 */
};
/***************************************************************************/
/*
*/
/*
installJoystick
*/
/*
*/
/* Install joystickHandler and increase interrupt
frequency. */
/*
*/
/***************************************************************************/
void installJoystick (void)
{
int numParagraphs;
int segment;
/* get current real mode timer isr */
if (__dpmi_get_real_mode_interrupt_vector (TIMER_VECTOR,
&oldVector))
printf ("Error: unable to get real mode interrupt\n");
/* determine number of paragraphs for new isr */
numParagraphs = (sizeof (joystickIsr) + 15) >> 4;
/* allocate dos memory for new isr */
segment = __dpmi_allocate_dos_memory (numParagraphs,
&joystickIsrSelector);
if (segment == -1)
printf ("Error: unable to allocate dos memory\n");
/* set new isr's segment and old vector address */
*(short*)(joystickIsr + 0x05) = segment;
*(short*)(joystickIsr + 0x72) = oldVector.offset16;
*(short*)(joystickIsr + 0x74) = oldVector.segment;
/* copy new isr into dos memory */
dosmemput (joystickIsr, sizeof (joystickIsr), segment << 4);
/* configure new isr vector address */
newVector.offset16 = 0x0000;
newVector.segment = segment;
/* set new real mode timer isr */
if (__dpmi_set_real_mode_interrupt_vector (TIMER_VECTOR,
&newVector))
printf ("Error: unable to set real mode interrupt\n");
/* set counter 0 to 6206.2 interrupts/sec */
asm ("cli");
asm ("movb $0x36,%al");
asm ("outb %al,$0x43");
asm ("movb $0xC0,%al");
asm ("outb %al,$0x40");
asm ("movb $0x00,%al");
asm ("outb %al,$0x40");
asm ("sti");
/* configure protected mode pointers to real mode data (must have
previously enabled near pointers) - i.e. joystickX points to
JOYX,
joystickY to JOYY and joystickButtons to JOYBUTTONS */
joystickX = (int*)(__djgpp_conventional_base + (segment << 4) +
0x78);
joystickY = (int*)(__djgpp_conventional_base + (segment << 4) +
0x7C);
joystickButtons = (int*)(__djgpp_conventional_base + (segment << 4)
+ 0x80);
}
/***************************************************************************/
/*
*/
/*
removeJoystick
*/
/*
*/
/* Restore interrupt frequency and old interrupt
handler. */
/*
*/
/***************************************************************************/
void removeJoystick (void)
{
/* set counter 0 to 18.2 interrupts/sec */
asm ("cli");
asm ("movb $0x36,%al");
asm ("outb %al,$0x43");
asm ("movb $0x00,%al");
asm ("outb %al,$0x40");
asm ("movb $0x00,%al");
asm ("outb %al,$0x40");
asm ("sti");
/* restore original real mode timer isr */
if (__dpmi_set_real_mode_interrupt_vector (TIMER_VECTOR,
&oldVector))
printf ("Error: unable to set real mode interrupt\n");
/* free dos memory allocated for new isr */
if (__dpmi_free_dos_memory (joystickIsrSelector))
printf ("Error: unable to free dos memory\n");
}
/***************************************************************************/
/*
*/
/* This only shows how the above are used - you can't judge
performance */
/* from
this! */
/*
*/
/***************************************************************************/
void main (void)
{
if (!__djgpp_nearptr_enable ())
printf ("Error: unable to enable near pointers\n");
installJoystick ();
/* while no buttons pressed */
while (!*joystickButtons)
{
printf ("x = %x y = %x\n", *joystickX, *joystickY);
}
removeJoystick ();
}
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