From: Gero Timann <geti AT mcis DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: Reprogram the PIC under CWSDPMI ?
Date: Tue, 22 Sep 1998 12:17:26 +0200
Organization: MediaCompany Goe
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To: djgpp AT delorie DOT com
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Hello DJGPP-Fans !

For my PFDSP-Project i'm looking for a way to minimize the overhead in
an interrupt-routines. One way to save interrupt-time, is to leave out
EOI:
Messures:
1) saves about 2 microseconds from about 2.5 micro_s, great!
2)  under Win95(-DPMI) you can do this without problems, saves
 9micro_s on a    P166   - Win95 service seems to emulate this with IRET
  - standard dpmi-server like cwsdpmi, pmode or emm386 (DRDOS, very long
  interrupt-duration, not usable for my project)  don't do this, EOI is
  needed

Is there a way to reprogram the PIC (82C59A) to Automatic EOI-mode ?
The first idea

void pic_auto_eoi(char s1,char s2)
{ WORD buf;

  asm("cli");
  buf=pic_get_status();                       // save OCW1

  // Master
  outportb(0x20,0x11);                        // ICW1
  outportb(0x21,0x08);                        // ICW2
  outportb(0x21,0x04);                        // ICW3
  if (s1){                                    // ICW4
    outportb(0x21,0x03);PicAutoEOI[0]=1;
  }else{
    outportb(0x21,0x01);PicAutoEOI[0]=0;
  }

  // Slave
  outportb(0xA0,0x11);                        // ICW1
  outportb(0xA1,0x70);                        // ICW2
  outportb(0xA1,0x02);                        // ICW3
  if (s2){                                    // ICW4
    outportb(0xA1,0x03);PicAutoEOI[1]=1;
  }else{
    outportb(0xA1,0x01);PicAutoEOI[1]=0;
  }

  pic_set_status(buf);                        // Restore OCW1
  asm("sti");
}

does't work. Why ?

Thanks for your comments.

Regards,
Gero

--
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Dipl.Phys.Gero Timann
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37081 Göttingen
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Tel./Fax: Germany-0551-96782
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