Bitfields for BIOS equipment list:

^ Bit(s) ^ Description ^
| 0 | floppy disk(s) installed (number specified by bits 7-6) |
| 1 | 80x87 coprocessor installed |
| 3-2 | number of 16K banks of RAM on motherboard (PC only) |
| ::: | number of 64K banks of RAM on motherboard (XT only) |
| 2 | pointing device installed (PS) |
| 3 | unused (PS) |
| 5-4 | initial video mode |
| ::: | 00 EGA, VGA, or PGA |
| ::: | 01 40x25 color |
| ::: | 10 80x25 color |
| ::: | 11 80x25 monochrome |
| 7-6 | number of floppies installed less 1 (if bit 0 set) |
| 8 | DMA support installed (PCjr, Tandy 1400LT) |
| ::: | DMA support *not* installed (Tandy 1000's) |
| 11-9 | number of serial ports installed |
| 12 | game port installed |
| 13 | serial printer attached (PCjr) |
| ::: | internal modem installed (PC/Convertible) |
| 15-14 | number of parallel ports installed |

---Compaq, Dell, and many other 386/486 machines--
| 23 | page tables set so that Weitek coprocessor addressable in real mode |
| 24 | Weitek math coprocessor present |

---Compaq Systempro---
| 25 | internal DMA parallel port available |
| 26 | IRQ for internal DMA parallel port (if bit 25 set) |
| ::: | 0 = IRQ5 |
| ::: | 1 = IRQ7 |
| 28-27 | parallel port DMA channel |
| ::: | 00 DMA channel 0 |
| ::: | 01 DMA channel 0 ??? |
| ::: | 10 reserved |
| ::: | 11 DMA channel 3 |

Notes

  * Some implementations of Remote (Initial) Program Loader (RPL/RIPL) don't set bit 0 to indicate a "virtual" floppy drive, although the RPL requires access to its memory image through a faked drive A:. This may have caused problems with releases of DOS 3.3x and earlier,  which assumed A: and B: to be invalid drives then and would discard  any attempts to access these drives. Implementations of RPL should set bit 0 to indicate a "virtual" floppy.
  * The IBM PC DOS 3.3x-2000 IBMBIO.COM contains two occurrences of code sequences like:

	    INT 11h
	    JMP SHORT skip
	    DB 52h,50h,53h; "RPS"
	    skip: OR AX,1
	    TEST AX,1

While at the first glance this seems to be a bug since it just wastes memory and the condition is always true, this could well be a signature for an applyable patch to stop it from forcing AX bit 0 to be always on. MS-DOS IO.SYS does not contain these signatures, however.

BUGs

  * Some old BIOSes didn't properly report the count of floppy drives installed to the system.  In newer systems INT 13h/AH=15h can be used to retrieve the number of floppy drives installed.
  * Award BIOS v4.50G and v4.51PG erroneously set bit 0 even if there are no floppy drives installed; use two calls to INT 13/AH=15h to determine whether any floppies are actually installed

SeeAlso: INT 12"BIOS",#03215 at INT 4B"Tandy 2000"