| 0000-001F | PC/XT/AT | DMA | | DMA Controller 1 - Intel 8237 |
| 0000 | PC/XT/AT | DMA | r/w | DMA channel 0 address |
| 0001 | PC/XT/AT | DMA | r/w | DMA channel 0 word count |
| 0002 | PC/XT/AT | DMA | r/w | DMA channel 1 address |
| 0003 | PC/XT/AT | DMA | r/w | DMA channel 1 word count |
| 0004 | PC/XT/AT | DMA | r/w | DMA channel 2 address |
| 0005 | PC/XT/AT | DMA | r/w | DMA channel 2 word count |
| 0006 | PC/XT/AT | DMA | r/w | DMA channel 3 address |
| 0007 | PC/XT/AT | DMA | r/w | DMA channel 3 word count |
| 0008 | PC/XT/AT | DMA | r | DMA channel 0-3 status |
| 0008 | PC/XT/AT | DMA | w | DMA channel 0-3 command register |
| 0009 | PC/XT/AT | DMA | w | DMA write request register |
| 000A | PC/XT/AT | DMA | r/w | DMA channel 0-3 mask register |
| 000B | PC/XT/AT | DMA | w | DMA channel 0-3 mode register |
| 000C | PC/XT/AT | DMA | w | DMA clear byte pointer flip-flop |
| 000D | PC/XT/AT | DMA | r | DMA read temporary register |
| 000D | PC/XT/AT | DMA | w | DMA master clear |
| 000E | PC/XT/AT | DMA | w | DMA clear mask register |
| 000F | PC/XT/AT | DMA | w | DMA write mask register |
| 0020-003F | PC/XT/AT | PIC | | PIC 1 - Programmable Interrupt Controller - Intel 8259 |
| 0020 | PC/XT/AT | PIC | w | PIC Initialization command word ICW1 |
| 0021 | PC/XT/AT | PIC | w | PIC ICW2,ICW3,ICW4 after ICW1 to 0020 |
| 0021 | PC/XT/AT | PIC | r/w | PIC master interrupt mask register |
| 0020 | PC/XT/AT | PIC | r | PIC interrupt request/in-service registers by OCW3 |
| 0040-005F | PC/XT/AT | PIT | | PIT - Programmable Interrupt Timer - Intel 8253 or 8254 |
| 0040 | PC/XT/AT | PIT | r/w | PIT counter 0, counter divisor |
| 0041 | PC/XT/AT | PIT | r/w | PIT counter 1, RAM refresh counter (XT, AT) |
| 0042 | PC/XT/AT | PIT | r/w | PIT counter 2, cassette & speaker (XT, AT, PS/2) |
| 0043 | PC/XT/AT | PIT | r/w | PIT mode register for counters 0-2 |
| 0060-006F | PC/XT | PPI | r/w | PPI - Programmable Peripheral Interface - Intel 8255 |
| 0060-006F | AT | KBD | | Keyboard microcontroller - 804x (8041, 8042) |
| 0060 | PC/XT | PPI | r | PPI Port A |
| 0061 | AT | KBD | w | Keyboard microcontroller |
| 0061 | PC/XT | PPI | r | PPI Port B |
| 0062 | PC/XT | PPI | r/w | PPI Port C |
| 0063 | PC/XT | PPI | r/w | PPI Command Port |
| 0070-007F | PC/XT/AT | RTC | | CMOS RAM/RTC (Real Time Clock MC146818) |
| 0080-008F | PC/XT/AT | DMA | | DMA page registers (74612) |
| 0080 | PC/XT/AT | DMA | r/w | extra page register (temporary storage) |
| 0081 | PC/XT/AT | DMA | r/w | DMA channel 2 address byte 2 |
| 0082 | PC/XT/AT | DMA | r/w | DMA channel 3 address byte 2 |
| 0083 | PC/XT/AT | DMA | r/w | DMA channel 1 address byte 2 |
| 0084 | | DMA | r/w | extra page register |
| 0085 | | DMA | r/w | extra page register |
| 0086 | | DMA | r/w | extra page register |
| 0087 | | DMA | r/w | DMA channel 0 address byte 2 |
| 0088 | | DMA | r/w | extra page register |
| 0089 | | DMA | r/w | DMA channel 6 address byte 2 |
| 0089 | | DMA | r/w | DMA channel 7 address byte 2 |
| 0089 | | DMA | r/w | DMA channel 5 address byte 2 |
| 008C | | DMA | r/w | extra page register |
| 008D | | DMA | r/w | extra page register |
| 008E | | DMA | r/w | extra page register |
| 008F | | DMA | r/w | DMA refresh page register |
| 00A0-00AF | AT | PIC | | PIC 2 - Programmable Interrupt Controller - Intel 8259 |
| 00A0 | XT | NMI | r/w | NMI mask register (XT) |
| 00C0 | PCjr/Tandy | | | SN746496 programmable tone/noise generator |
| 00C0-00DF | AT | DMA | | DMA 2 - Direct Memory Access controller - Intel 8237 |
| 00F0-00F5 | PCjr | FDC | | PCjr Disk Controller |
| 00F0 | PCjr | FDC | | disk controller |
| 00F2 | PCjr | FDC | | disk controller control port |
| 00F4 | PCjr | FDC | | disk controller status register |
| 00F5 | PCjr | FDC | | disk controller data port |
| 00F0-00FF | AT | FPU | | FPU - Math Coprocessor (80287..80387) |
| 00F0 | AT | FPU | w | Math coprocessor clear busy latch |
| 00F1 | AT | FPU | w | Math coprocessor reset |
| 00F8 | AT | FPU | r/w | Math coprocessor opcode transfer |
| 00FA | AT | FPU | r/w | Math coprocessor opcode transfer |
| 0140-0157 | PC/XT/AT | RTC | | RTC (alternate Real Time Clock for XT) (1st at 0340-0357) |
| 0200-020F | PC/XT/AT | Game Port | | Game port |
| 0201 | PC/XT/AT | Game Port | r | Read joystick position and status |
| 0210-0217 | XT | Expansion | | Expansion unit (XT) |
| 0210 | XT | Expansion | w | latch expansion bus data |
| 0211 | XT | Expansion | w | clear wait, test latch |
| 0212 | XT | Expansion | r | Low byte data address |
| 0213 | XT | Expansion | w | 0=enable, 1=disable expansion unit |
| 0214 | XT | Expansion | w | latch data (receiver card port) |
| 0215 | XT | Expansion | r | High byte of address, then Low byte (receiver card port) |
| 0220-0223 | PC/XT/AT | Sound | | Sound Blaster / Adlib port |
| 0220 | PC/XT/AT | Sound | r/w | Left speaker – Status / Address port |
| 0221 | PC/XT/AT | Sound | w | Left speaker – Data port |
| 0222 | PC/XT/AT | Sound | r/w | Right speaker – Status / Address port |
| 0223 | PC/XT/AT | Sound | w | Right speaker – Data port |
| 0220-0227 | PC/XT/AT | Sound | | Soundblaster PRO and SSB 16 ASP |
| 0220-022F | PC/XT/AT | Sound | | Soundblaster PRO 2.0 |
| 0220-022F | PC/XT/AT | Sound | | Soundblaster PRO 4.0 |
| 0220 | PC/XT/AT | Sound | r | left FM status port |
| 0220 | PC/XT/AT | Sound | w | left FM music register address port (index) |
| 0221 | PC/XT/AT | Sound | r/w | left FM music data port |
| 0222 | PC/XT/AT | Sound | r | right FM status port |
| 0222 | PC/XT/AT | Sound | w | right FM music register address port (index) |
| 0223 | PC/XT/AT | Sound | r/w | right FM music data port |
| 0224 | PC/XT/AT | Sound | w | mixer register address port (index) |
| 0225 | PC/XT/AT | Sound | r/w | mixer data port |
| 0226 | PC/XT/AT | Sound | w | DSP reset |
| 0228 | PC/XT/AT | Sound | r | FM music status port |
| 0228 | PC/XT/AT | Sound | w | FM music register address port (index) |
| 0229 | PC/XT/AT | Sound | w | FM music data port |
| 022A | PC/XT/AT | Sound | r | DSP read data (voice I/O and Midi) |
| 022C | PC/XT/AT | Sound | w | DSP write data / write command |
| 022C | PC/XT/AT | Sound | r | DSP write buffer status (bit 7) |
| 022E | PC/XT/AT | Sound | r | DSP data available status (bit 7) |
| 0240-024F | PC/XT/AT | Sound | | Gravis UltraSound |
| 0240-0257 | AT/XT | RTC | | RTC (alternate Real Time Clock for XT) (1st at 0340-0357) |
| 0258-025F | PC/XT/AT | Memory | | Intel Above Board |
| 0278-027E | PC/XT/AT | Parallel | | Parallel printer port, same as 0378 and 03BC |
| 0278 | PC/XT/AT | Parallel | w | data port |
| 0279 | PC/XT/AT | Parallel | r/w | status port |
| 027A | PC/XT/AT | Parallel | r/w | control port |
| 02A2-02A3 | PC/XT/AT | RTC | | MSM58321RS clock |
| 02B0-02DF | AT | Video | | Alternate EGA IO addresss (Primary at 3BX) - Basically unused |
| 02E0-02EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| 02E1 | PC/XT/AT | GPIB | | GPIB (adapter 0) |
| 02E0-02EF | AT | GPIB | | data aquisition (AT) |
| 02E2 | PC/XT/AT | GPIB | | data aquisition (adapter 0) |
| 02E3 | PC/XT/AT | GPIB | | data aquisition (adapter 0) |
| 02E8-02EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 02F8-02FF | PC/XT/AT | Serial | | Serial port, same as 02E8, 03E8 and 03F8 |
| 02F8 | PC/XT/AT | Serial | w | transmitter holding register |
| 02F8 | PC/XT/AT | Serial | r | receiver buffer register |
| 02F9 | PC/XT/AT | Serial | r/w | divisor latch, high byte when DLAB=1 |
| 02FA | PC/XT/AT | Serial | r | interrupt identification register |
| 02FB | PC/XT/AT | Serial | r/w | line control register |
| 02FC | PC/XT/AT | Serial | r/w | modem control register |
| 02FD | PC/XT/AT | Serial | r | line status register |
| 02FF | PC/XT/AT | Serial | r/w | scratch register |
| 0300 | AT | Diag | | Award BIOS - POST Diagnostic |
| 0300-0301 | PC/XT/AT | Sound | | Soundblaster 16 ASP MPU-Midi |
| 0320-0323 | XT | HDC | | XT Hard Disk Controller 1 |
| 0320 | PC/XT/AT | HDC | r/w | data register |
| 0321 | PC/XT/AT | HDC | w | reset controller |
| 0322 | XT | HDC | r | read DIPswitch setting on XT controller card |
| 0323 | PC/XT/AT | HDC | w | write pattern to DMA and INT mask register |
| 0324-0327 | XT | HDC | | XT Hard Disk Controller 2 |
| 0328-032B | XT | HDC | | XT Hard Disk Controller 3 |
| 032C-032F | XT | HDC | | XT Hard Disk Controller 4 |
| 0330-0331 | PC/XT/AT | Sound | | MIDI interface |
| 0338 | PC/XT/AT | Sound | | AdLib FM Synthesis Card |
| 0340-034F | PC/XT/AT | Sound | | Gravis UltraSound (DIP option) |
| 0340-0357 | PC/XT | RTC | | RTC (1st Real Time Clock for XT), (alternate at 0240-0257) |
| 0348-0357 | PC/XT/AT | | | DCA 3278 |
| 034C-034F | PC/XT/AT | Sound | | Gravis UltraMax (DIP Option) |
| 0360-036F | AT/XT | | | PC network (AT) |
| 0360-0367 | XT | | | PC network (XT only) |
| 0370-0377 | AT | FDC | | FDC 2 (2nd Floppy Disk Controller) first FDC at 03F0 |
| 0370 | | FDC | r | diskette Extra High Density controller board jumpers (AT) |
| 0372 | | FDC | w | diskette controller DOR (Digital Output Register) |
| 0374 | | FDC | r | diskette controller main status register |
| 0374 | | FDC | w | diskette controller datarate select register |
| 0375 | | FDC | r/w | diskette controller command/data register |
| 0376 | | FDC | r/w | (2nd FIXED disk controller data register) |
| 0377 | | FDC | r | diskette controller DIR (Digital Input Register) |
| 0377 | | FDC | w | select register for diskette data transfer rate |
| 0378-037A | PC/XT/AT | Parallel | | Parallel printer port (LPT1) - See also 0278 and 03BC |
| 0378 | | Parallel | w | data port |
| 0379 | | Parallel | r/w | status port |
| 037A | | Parallel | r/w | control port |
| 0388-0389 | PC/XT/AT | Sound | | Sound Blaster / Adlib port |
| 0388 | PC/XT/AT | Sound | r/w | Both Speakers – Status / Address port |
| 0389 | PC/XT/AT | Sound | w | Data port |
| 03B0-03BF | PC/XT/AT | Video | | MDA (Monochrome Display Adapter based on 6845) |
| 03B0 | PC/XT/AT | Video | | same as 03B4 |
| 03B1 | PC/XT/AT | Video | | same as 03B5 |
| 03B2 | PC/XT/AT | Video | | same as 03B4 |
| 03B3 | PC/XT/AT | Video | | same as 03B5 |
| 03B4 | PC/XT/AT | Video | w | MDA CRTC index register |
| 03B5 | PC/XT/AT | Video | r/w | MDA CRTC data register |
| 03B6 | PC/XT/AT | Video | | same as 03B4 |
| 03B7 | PC/XT/AT | Video | | same as 03B5 |
| 03B8 | PC/XT/AT | Video | r/w | MDA mode control register |
| 03B9 | PC/XT/AT | Video | | reserved for color select register on color adapter |
| 03BA | PC/XT/AT | Video | r | CRT status register EGA/VGA: input status 1 register |
| 03BA | PC/XT/AT | Video | w | EGA/VGA feature control register |
| 03BB | PC/XT/AT | Video | | reserved for light pen strobe reset |
| 03BC-03BF | PC/XT/AT | Video | | Parallel printer port, same as 0278 and 0378 |
| 03BC | PC/XT/AT | Video | w | data port |
| 03BD | PC/XT/AT | Video | r/w | status port |
| 03BE | PC/XT/AT | Video | r/w | control port |
| 03BF | | Video | r/w | Hercules configuration switch register |
| 03C0-03CF | | Video | | EGA (1st Enhanced Graphics Adapter) alternate at 02C0 |
| 03C0 | | Video | | (r)/w EGA VGA ATC index/data register |
| 03C1 | | Video | r | VGA other attribute register |
| 03C2 | | Video | r | EGA VGA input status 0 register |
| 03C3 | | Video | r/w | VGA video subsystem enable (see also port 46E8h) |
| 03C4 | | Video | w | EGA TS index register |
| 03C5 | | Video | w | EGA TS data register |
| 03C6 | | Video | r/w | VGA PEL mask register |
| 03C7 | | Video | r/w | VGA PEL address read mode |
| 03C8 | | Video | r/w | VGA PEL address write mode |
| 03C9 | | Video | r/w | VGA PEL data register |
| 03CA | | Video | w | EGA graphics 2 position register |
| 03CC | | Video | w | EGA graphics 1 position register |
| 03CE | | Video | w | EGA GDC index register |
| 03CF | | Video | w | EGA GDC data register |
| 03D0-03DF | | Video | | CGA (Color Graphics Adapter) |
| 03D0 | | Video | | same as 03D4 |
| 03D1 | | Video | | same as 03D5 |
| 03D2 | | Video | | same as 03D4 |
| 03D3 | | Video | | same as 03D5 |
| 03D4 | | Video | w | CRTC (6845) index register (EGA/VGA) |
| 03D5 | | Video | w | CRTC (6845) data register (EGA/VGA) |
| 03D6 | | Video | | same as 03D4 |
| 03D7 | | Video | | same as 03D5 |
| 03D8 | | Video | r/w | CGA mode control register (except PCjr) |
| 03D9 | | Video | r/w | CGA palette register |
| 03DA | | Video | r | CGA status register |
| 03DA | | Video | r | EGA/VGA input status 1 register |
| 03DA | | Video | w | EGA/VGA feature control register |
| 03DB | | Video | w | clear light pen latch |
| 03DC | | Video | r/w | preset light pen latch |
| 03DF | PCjr | System | | CRT/CPU page register (PCjr only) |
| 03E8-03EF | PC/XT/AT | Serial | | serial port, same as 02E8, 02F8 and 03F8 |
| 03F0-03F7 | AT | FDC | | FDC 1 (1st Floppy Disk Controller) - second FDC at 0370 |
| 03F0 | PC/XT/AT | FDC | r | diskette EHD controller board jumper settings (82072AA) |
| 03F2 | PC/XT/AT | FDC | w | diskette controller DOR (Digital Output Register) |
| 03F3 | PC/XT/AT | FDC | | tape drive register (on the 82077AA) |
| 03F4 | PC/XT/AT | FDC | r | diskette controller main status register |
| 03F4 | PC/XT/AT | FDC | w | diskette controller data rate select register |
| 03F5 | PC/XT/AT | FDC | r | diskette command/data register 0 (ST0) |
| 03F5 | PC/XT/AT | FDC | w | diskette command register |
| 03F6 | PC/XT/AT | FDC | r/w | FIXED disk controller data register |
| 03F7 | PC/XT/AT | FDC | r/w | harddisk controller |
| 03F7 | AT/XT | FDC | r | diskette controller DIR (Digital Input Register, PC/AT mode) |
| 03F7 | AT/XT | FDC | w | configuration control register (PC/AT, PS/2) |
| 03F8-03FF | PC/XT/AT | Serial | | Serial port (8250,8251,16450,16550,16550A,etc.) |
| 03F8 | PC/XT/AT | Serial | w | Serial port, transmitter holding register |
| 03F9 | PC/XT/AT | Serial | r/w | Serial port, divisor latch high byte when DLAB==1 |
| 03F9 | PC/XT/AT | Serial | r/w | Serial port, interrupt enable register when DLAB==0 |
| 03FA | PC/XT/AT | Serial | r | Serial port, interrupt identification register |
| 03FA | PC/XT/AT | Serial | w | 16650 FCR (FIFO Control Register) |
| 03FB | PC/XT/AT | Serial | r/w | line control register |
| 03FC | PC/XT/AT | Serial | r/w | modem control register |
| 03FD | PC/XT/AT | Serial | r | line status register |
| 03FE | PC/XT/AT | Serial | r | modem status register |
| 03FF | PC/XT/AT | Serial | r/w | scratch register |
| 0530-0533 | PC/XT/AT | Sound | | Gravis UltraSound Daughter Card |
| 0620-0627 | XT | Network | | PC network (adapter 1) |
| 0628-062F | XT | Network | | PC network (adapter 2) |
| 0680 | PC/XT/AT | System | w | Microchannel POST Diagnostic |
| 06E8-06EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 0746 | PC/XT/AT | Sound | | Gravis UltraSound |
| 0800-08FF | PC/XT/AT | System | | I/O port access registers for extended CMOS RAM or SRAM |
| 0A20-0A23 | PC/XT/AT | Network | | Token Ring (adapter 1) |
| 0A24-0A27 | PC/XT/AT | Network | | Token Ring (adapter 2) |
| 0AE8-0AEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 0EE8-0EEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 12E8-12EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 16E8-16EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 1AE8-1AEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 1EE8-1EEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 2100-210F | PC/XT/AT | Video | | IBM XGA (eXtended Graphics Adapter 8514/A) (first installed) |
| 2110-217F | PC/XT/AT | Video | | secondary XGA adapters |
| 22E8-22EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 3220-3227 | PC/XT/AT | Serial | | serial port 3, description same as 03F8 |
| 3228-322F | PC/XT/AT | Serial | | serial port 4, description same as 03F8 |
| 3540-354F | PC/XT/AT | SCSI | | IBM SCSI (Small Computer System Interface) adapter |
| 3550-355F | PC/XT/AT | SCSI | | IBM SCSI (Small Computer System Interface) adapter |
| 3560-356F | PC/XT/AT | SCSI | | IBM SCSI (Small Computer System Interface) adapter |
| 3570-357F | PC/XT/AT | SCSI | | IBM SCSI (Small Computer System Interface) adapter |
| 4220-4227 | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| 4228-422F | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| 42E0-42EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| 46E8 | PC/XT/AT | Video | | VGA video adapter enable |
| 4AE8-4AEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 5220-5227 | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| 5228-522F | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| 62E0-62EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| 82E0-82EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| 82E8-82EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 8AE8-8AEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 8EE8-8EEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 92E8-92EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| 96E8-96EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| A2E0-A2EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| A2E8-A2EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| A6E8-A6EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| AAE8-AAEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| AEE8-AEEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| B220-B227 | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| B228-B22F | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| B2E8-B2EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| B6E8-B6EF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| BAE8-BAEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| BEE8-BEEF | PC/XT/AT | Video | | 8514/A and compatible video cards |
| C220-C227 | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| C228-C22F | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| C2E0-C2EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| D220-D227 | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| D228-D22F | PC/XT/AT | Serial | | serial port, description same as 03F8 |
| E2E0-E2EF | PC/XT/AT | GPIB | | GPIB (General Purpose Interface Bus, IEEE 488 interface) |
| E2E8-E2EF | PC/XT/AT | Video | | 8514/A and compatible video cards |