Message-ID: <37A800B1.D4B0B30C@softhome.net>
Date: Wed, 04 Aug 1999 10:58:25 +0200
From: Laurynas Biveinis <lauras AT softhome DOT net>
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To: DJGPP Workers <djgpp-workers AT delorie DOT com>
Subject: CPU ID program, second version
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Reply-To: djgpp-workers AT delorie DOT com

Hello,

if all what "uname -m" has to do is print i[3-6]86,
then this program below should do it correctly. I
went to AMD and Cyrix web sites, fetched docs and
added support for these CPU, but is it necesarry
at all? If no - prg below should do the trick. If
yes - there is extended version which detects CPU
vendor. Just tell me.

So the main difference from previous prg is removed
check for "GenuineIntel" and generic check for 
CPU instruction family with CPUID is used instead.

Laurynas Biveinis
-----------------
/* CPU type under DJGPP checker, v1.1alpha     */
/* (C) 1999 Laurynas Biveinis                  */
/* Uses CPU detection routines by Phil Frisbie */

#include <stdio.h>

int main(void)
{
   unsigned is_486_or_better;
   unsigned supports_cpuid;
   unsigned vendor_id[3];
   unsigned version_info;

   /* Let's check for 386. Intel says that 386 is unable to set or clear */
   /* value of 18 bit in EFLAGS (AC). So we toggle this bit and see if   */
   /* we succeed */
   asm volatile (
       "pushf;"                       /* save EFLAGS */
       "popl   %%eax;"                /* get EFLAGS */
       "movl   %%eax, %%ebx;"         /* temp storage EFLAGS */
       "xorl   $0x40000, %%eax;"      /* change AC bit in EFLAGS */
       "pushl  %%eax;"                /* put new EFLAGS value on stack */
       "popf;"                        /* replace current EFLAGS value */
       "pushf;"                       /* get EFLAGS */
       "popl   %%eax;"                /* save new EFLAGS in EAX */
       "cmpl   %%ebx, %%eax;"         /* compare temp and new EFLAGS */
       "jz     0f;"
       "movl   $1, %0;"               /* 80486+ present */
       "jmp    1f;"
       "0:"
       "movl   $0, %0;"               /* 80386 present */
       "1:"
       "pushl  %%ebx;"                /* get original EFLAGS */
       "popf;"                        /* restore EFLAGS */
       : "=g" (is_486_or_better)
       :
       : "eax", "ebx");
   if (is_486_or_better)
   {
      /* In the same way we checked for 386, we will check for 486 now, */
      /* using 21 bit in EFLAGS (ID bit)      */
      asm volatile (
         "pushf;"                      /* get extended flags */
         "popl     %%eax;"
         "movl     %%eax, %%ebx;"       /* save current flags */
         "xorl     $0x200000, %%eax;"   /* toggle bit 21 */
         "pushl    %%eax;"              /* put new flags on stack */
         "popfl;"                       /* flags updated now in flags */
         "pushfl;"                      /* get extended flags */
         "popl     %%eax;"
         "xorl     %%ebx, %%eax;"       /* if bit 21 r/w then supports cpuid */
         "jz       0f;"
         "movl     $1, %0;"
         "jmp      1f;"
         "0:"
         "movl     $0, %0;"
         "1:"
         : "=g" (supports_cpuid)
         :
         : "%eax", "%ebx");
         if (supports_cpuid)
         {
            /* Now we can use CPUID */
            asm volatile (
               "movl   $1, %%eax;"
               "cpuid;"
               : "=a" (version_info)
               :
               : "%ebx", "%ecx", "%edx");
               /* What we need is family info in 8-11 bits */
               version_info = (version_info & 0x780) >> 8;
               switch (version_info)
               {
                  case 0x6: printf("i686\n"); break;
                  case 0x5: printf("i586\n"); break;
                  case 0x4: printf("i486\n"); break;
               }
         }
         else
            printf("i486\n");
   }
   else
      printf("i386\n");
   return 0;
}