From: csantill AT lausd DOT k12 DOT ca DOT us
Message-ID: <33D2CFCB.4A39@lausd.k12.ca.us>
Date: Sun, 20 Jul 1997 19:56:11 -0700
MIME-Version: 1.0
To: dj AT delorie DOT com, djgpp AT delorie DOT com
Subject: Re: Is the FAQ wrong about FAR/NEAR ptr speed
References: <199707210027 DOT UAA09914 AT delorie DOT com>
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DJ Delorie wrote:
> 
> Remember that VGA memory is so slow it often doesn't matter how fast
> your code is.  Try copying to/from DOS memory and see how fast it is.
Do you mean(in pseudo code)
for y
  for x
    put pix
    get pix

Well, I now tested as put pix & then get pix in buff[200][320]. The put
pix timings & get pix timings as seperate timings but I get the exact
same fps rate(24.98 GFPS-get frames per sec).  I think I'll try the
pseudo code above next & see if there is a difference though I doubt
there will be.  I have a Q's though before I give you my new code, I've
heard about descriptors & would to know a few things about it.  Can I
full source on how to do it correct(my hack off the FAQ didn't seem to
work)?  Is it "faster" & safer?
Thanx for your input DJ.
Here's my code.

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#include <sys/farptr.h>
#include <sys/nearptr.h>
#include <dpmi.h>
#include <go32.h>

#include <time.h>

#include <stdlib.h>

#include <string.h>
#include <stdio.h>
// The includes are from my original file - circle/box/line snipped out
// I owe a big thanx to Sinan for my receipt of some actually working VGA
//   code. THAAAAAAAAAAAAAAAANNNNNNNNXXXXXXXXXXXXXXXXXXX!!!!!!!!!!!!! :]

enum GR_MODE{GR_INVALID=-1, GR_TEXT=0x03, GR_VGA=0x13};

enum GR_MODE Set_GR_Mode(enum GR_MODE mode)
{
  __dpmi_regs r;

  memset(&r, 0, sizeof(r));
  r.x.ax=mode;

  return(__dpmi_int(0x10,&r) ? GR_INVALID:mode);
}
// ************************************************************************
void Put_Pix_Far(int x, int y, char c)
{
  _farpokeb(_dos_ds, 0xA0000+(y<<8)+(y<<6)+x,c);
  return;
}
// ************************************************************************
char Get_Pix_Far(int x, int y)
{
  return _farpeekb(_dos_ds, 0xA0000+(y<<8)+(y<<6)+x);
}
// ************************************************************************
void Put_Pix_Near(int x, int y, char c)
{
  char *v_m=(char *)(0xA0000+__djgpp_conventional_base);
  v_m[(y<<8)+(y<<6)+x] = c;
}
// ************************************************************************
char Get_Pix_Near(int x, int y)
{
  char *v_m=(char *)(0xA0000+__djgpp_conventional_base);
  return v_m[(y<<8)+(y<<6)+x];
}
// ************************************************************************
int main(void)
{
  int x, y, co;
  uclock_t st1, st2, et1, et2;
  char vid_mem_capture_buff[200][320];

  if(GR_INVALID==Set_GR_Mode(GR_VGA))
  {
    printf("Error setting mode 13h\n");
    exit(8);
  }

// Beginning of FAR PTR SPEED TEST
  st1=uclock();
  for(co=0; co<7680; co++)
    for(y=0; y<200; y++)
      for(x=0; x<320; x++)
        Put_Pix_Far(x,y,co % 256);
  et1=uclock();
// Ending of FAR PTR SPEED TEST

  printf("Done w/FAR PTR set_pix test\nHit ENTER to start NEAR PTR"
    " set_pix TEST\n");
  getchar();

// Beginning of NEAR PTR SPEED TEST
  if(__djgpp_nearptr_enable())
    {
      st2=uclock();
      for(co=0; co<7680; co++)
        for(y=0; y<200; y++)
          for(x=0; x<320; x++)
            Put_Pix_Near(x,y,co % 256);
      et2=uclock();
     };
  __djgpp_nearptr_disable();
// Ending of NEAR PTR SPEED TEST
  Set_GR_Mode(GR_TEXT);

// Show the results
  printf("On my Pentium 120, 16MB RAM, Trident ET6???? w/1MB, while using"
    " RHIDE 1.3, GCC\n2.7 w/-O9 & -m386(-m486 I get the same results), I get"
    " 24.98 fps for both test.\nIs this unusual?\n\nYour results:\n");
// FAR PTR results
  printf("FPS for FAR PTR set_pix = %3.2f\n",
    (float)7680/((float)((et1-st1)/UCLOCKS_PER_SEC)));
// NEAR PTR results
  printf("FPS for NEAR PTR set_pix= %3.2f\n",
    (float)7680/((float)((et2-st2)/UCLOCKS_PER_SEC)));
  printf("\n\nHit ENTER to start Get_Pix speed test\n");
  getchar(); */

// GET PIX TESTS
  if(GR_INVALID==Set_GR_Mode(GR_VGA))
  {
    printf("Error setting mode 13h\n");
    exit(8);
  }

// Beginning of FAR PTR SPEED TEST
  st1=uclock();
  for(co=0; co<7680;co++)
    for(y=0; y<200; y++)
      for(x=0; x<320; x++)
        vid_mem_capture_buff[y][x]=Get_Pix_Far(x,y);
  et1=uclock();
// Ending of FAR PTR SPEED TEST

  printf("Done w/FAR PTR get_pix test\nHit ENTER to start NEAR PTR"
    " set_pix TEST\n");

  getchar();

  for(co=0;co<25;co++) printf("\n");

// Beginning of NEAR PTR SPEED TEST
  if(__djgpp_nearptr_enable())
    {
      st2=uclock();
      for(co=0; co<7680; co++)
        for(y=0; y<200; y++)
          for(x=0; x<320; x++)
            vid_mem_capture_buff[y][x]=Get_Pix_Near(x,y);
      et2=uclock();
     };
  __djgpp_nearptr_disable();
// Ending of NEAR PTR SPEED TEST

  Set_GR_Mode(GR_TEXT);

// Show the results
  printf("On my Pentium 120, 16MB RAM, Trident ET6???? w/1MB, while using"
    " RHIDE 1.3, GCC\n2.7 w/-O9 & -m386(-m486 I get the same results), I get"
    " 90.35 fps for both test.\nIs this unusual?\n\nYour results:\n");
// FAR PTR results
  printf("FPS for FAR PTR get_pix = %3.2f\n",
    (float)7680/((float)((et1-st1)/UCLOCKS_PER_SEC)));
// NEAR PTR results
  printf("FPS for NEAR PTR get_pix= %3.2f\n",
    (float)7680/((float)((et2-st2)/UCLOCKS_PER_SEC)));

  getchar();

  return 0;

}

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