en:docs:bios:api:00226

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en:docs:bios:api:00226 [2023/12/16 15:29] – created prokusheven:docs:bios:api:00226 [2023/12/16 15:33] (current) – prokushev
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 ^ Bit(s) ^ Description ^ ^ Bit(s) ^ Description ^
-| 0 | floppy disk(s) installed (number specified by bits 7-6) | +| 0 | floppy disk(s) installed (number specified by bits 7-6) | 
-| 1 | 80x87 coprocessor installed | +| 1 | 80x87 coprocessor installed | 
-| 3-2 | number of 16K banks of RAM on motherboard (PC only) | +| 3-2 | number of 16K banks of RAM on motherboard (PC only) | 
-| ::: | number of 64K banks of RAM on motherboard (XT only) | +| ::: | number of 64K banks of RAM on motherboard (XT only) | 
-| 2 | pointing device installed (PS) | +| 2 | pointing device installed (PS) | 
-| 3 | unused (PS) | +| 3 | unused (PS) | 
-| 5-4 | initial video mode | +| 5-4 | initial video mode | 
-| ::: | 00 EGA, VGA, or PGA | +| ::: | 00 EGA, VGA, or PGA | 
-| ::: | 01 40x25 color | +| ::: | 01 40x25 color | 
-| ::: | 10 80x25 color | +| ::: | 10 80x25 color | 
-| ::: | 11 80x25 monochrome | +| ::: | 11 80x25 monochrome | 
-| 7-6 | number of floppies installed less 1 (if bit 0 set) | +| 7-6 | number of floppies installed less 1 (if bit 0 set) | 
-| 8 | DMA support installed (PCjr, Tandy 1400LT) | +| 8 | DMA support installed (PCjr, Tandy 1400LT) | 
-| ::: | DMA support *not* installed (Tandy 1000's) | +| ::: | DMA support *not* installed (Tandy 1000's) | 
-| 11-9 | number of serial ports installed | +| 11-9 | number of serial ports installed | 
-| 12 | game port installed | +| 12 | game port installed | 
-| 13 | serial printer attached (PCjr) | +| 13 | serial printer attached (PCjr) | 
-| ::: | internal modem installed (PC/Convertible) |+| ::: | internal modem installed (PC/Convertible) |
 | 15-14 | number of parallel ports installed | | 15-14 | number of parallel ports installed |
  
 ---Compaq, Dell, and many other 386/486 machines-- ---Compaq, Dell, and many other 386/486 machines--
- 23 page tables set so that Weitek coprocessor addressable in real mode +| 23 | page tables set so that Weitek coprocessor addressable in real mode | 
- 24 Weitek math coprocessor present+| 24 | Weitek math coprocessor present |
  
 ---Compaq Systempro--- ---Compaq Systempro---
- 25 internal DMA parallel port available +| 25 | internal DMA parallel port available | 
- 26 IRQ for internal DMA parallel port (if bit 25 set) +| 26 | IRQ for internal DMA parallel port (if bit 25 set) | 
- 0 = IRQ5 +| ::: | 0 = IRQ5 | 
- 1 = IRQ7 +| ::: | 1 = IRQ7 | 
- 28-27 parallel port DMA channel +| 28-27 | parallel port DMA channel | 
- 00 DMA channel 0 +| ::: | 00 DMA channel 0 | 
- 01 DMA channel 0 ??? +| ::: | 01 DMA channel 0 ??? | 
- 10 reserved +| ::: | 10 reserved | 
- 11 DMA channel 3+| ::: | 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:
  
-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      INT 11h
      JMP SHORT skip      JMP SHORT skip
Line 51: Line 47:
      skip: OR AX,1      skip: OR AX,1
      TEST 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 +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. 
-   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, +BUGs 
-   however. + 
-BUGs: Some old BIOSes didn't properly report the count of floppy drives +  * 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. 
-   installed to the system.  In newer systems INT 13h/AH=15h can be +  * 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
-   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" SeeAlso: INT 12"BIOS",#03215 at INT 4B"Tandy 2000"