// There are 1024 pages in each map. In the normal 64k page size that means a max of
// 64Mib of memory for an app. Since there is 512MB ram in the system that equates
// to 8192 x 64k pages.
#define NPAGES   8192
private __int16 pam[NPAGES];   // page allocation map (links like a DOS FAT)
// There are 128, 4MB pages in the system. Each 4MB page is composed of 64 64kb pages.
private int pam4mb[NPAGES/64];   // 4MB page allocation map (bit for each 64k page)
private __int16 freelist;
int syspages;               // number of pages reserved at the start for the system
int sys_pages_available;   // number of available pages in the system
int sys_4mbpages_available;

pascal int alloc_sys_page()
{
    int sb, pg4;

   if (freelist < syspages || freelist >= NPAGES)
      return 0xffff;
   sb = freelist;
   freelist = pam[freelist];
   sys_pages_available--;
   pg4 = (sb >> 6);
   pam4mb[pg4] |= (1 << (sb & 63));
   return sb;
}
 

void BIOSMain()
{
   float pi = 3.1415926535897932384626;
   float a,b;
   int btn;
   int seln=0;

   DBGAttr = 0x087FC00;//0b0000_1000_0111_1111_1100_0000_0000;
   DBGClearScreen();
   DBGHomeCursor();
   DBGDisplayString("  DSD9 Bios Started\r\n");
   DBGDisplayString("  Menu\r\n  up = ramtest\r\n  left = float test\r\n  right=TinyBasic\r\n");
   forever {
      //0b0000_1000_0111_1111_1100_0000_0000;
      //0b1111_1111_1000_0100_0000_0000_0000;
      btn = GetButton();
      switch(btn) {
      case BTNU:
         while(GetButton());
         ramtest();
         break;
      case BTNL:
         while(GetButton());
         FloatTest();
         break;
      case BTNR:
         while(GetButton());
         asm {
            jmp   TinyBasicDSD9
         };
         break;
      }
   }
}