Click above to get retro games delivered to your door ever month!

 I/O port address table
------------------------------------------------------------------------------
 Note that this summary does not replace consulting a detailed hardware
 reference before directly accessing I/O ports.

 000-00F 8237 DMA controller
     000 Channel 0 address register
     001 Channel 0 word count
     002 Channel 1 address register
     003 Channel 1 word count
     004 Channel 2 address register
     005 Channel 2 word count
     006 Channel 3 address register
     007 Channel 3 word count
     008 Status/command register
     009 Request register
     00A Mask register
     00B Mode register
     00C Clear MSB/LSB flip flop
     00D Master clear temp register
     00E Clear mask register
     00F Multiple mask register

 010-01F 8237 DMA Controller (PS/2 model 60 & 80), reserved (AT)

 020-02F 8259A Master Programmable Interrupt Controller
     020 8259 Command port
     021 8259 Interrupt mask register

 030-03F 8259A Slave Programmable Interrupt Controller (AT,PS/2)

 040-05F 8253 or 8254 Programmable Interval Timer (PIT)
     040 8253 channel 0, counter divisor
     041 8253 channel 1, RAM refresh counter
     042 8253 channel 2, Cassette and speaker functions
     043 8253 mode control
     044 8254 PS/2 extended timer
     047 8254 Channel 3 control byte

 060-067 8255 Programmable Peripheral Interface  (PC,XT, PCjr)
     060 8255 Port A keyboard input/output buffer (output PCjr)
     061 8255 Port B output
     062 8255 Port C input
     063 8255 Command/Mode control register

 060-06F 8042 Keyboard Controller  (AT,PS/2)
     060 8042 Keyboard input/output buffer register
     061 8042 system control port (for compatibility with 8255)
     064 8042 Keyboard command/status register

     070 CMOS RAM/RTC, also NMI enable/disable (AT,PS/2)
     071 CMOS RAM data (AT,PS/2)
     080 Manufacturer systems checkpoint port (used during POST)

 080-090 DMA Page Registers
     081 High order 4 bits of DMA channel 2 address
     082 High order 4 bits of DMA channel 3 address
     083 High order 4 bits of DMA channel 1 address

 090-097 POS/Programmable Option Select (PS/2)
     090 Central arbitration control Port
     091 Card selection feedback
     092 System control and status register
     094 System board enable/setup register
     095 Reserved
     096 Adapter enable/setup register
     097 Reserved

     0A0 NMI Mask Register (PC,XT)

 0A0-0BF Second 8259 Programmable Interrupt Controller (AT, PS/2)
     0A0 Second 8259 Command port
     0A1 Second 8259 Interrupt mask register

     0C0 TI SN76496 Programmable Tone/Noise Generator (PCjr)

 0C0-0DF 8237 DMA controller 2 (AT)
     0C2 DMA channel 3 selector

 0E0-0EF Reserved

 0F0-0FF Math coprocessor (AT, PS/2)

 0F0-0F5 PCjr Disk Controller
     0F0 Disk Controller
     0F2 Disk Controller control port
     0F4 Disk Controller status register
     0F5 Disk Controller data port

 0F8-0FF Reserved for future microprocessor extensions

 100-10F POS Programmable Option Select (PS/2)
     100 POS Register 0, Adapter ID byte (LSB)
     101 POS Register 1, Adapter ID byte (MSB)
     102 POS Register 2, Option select data byte 1
     103 POS Register 3, Option select data byte 2
     104 POS Register 4, Option select data byte 3
     105 POS Register 5, Option select data byte 4
     106 POS Register 6, subaddress extension (LSB)
     107 POS Register 7, subaddress extension (MSB)

 110-1EF System I/O channel

 170-17F Fixed disk 1 (AT)
     170 Disk 1 data
     171 Disk 1 error
     172 Disk 1 sector count
     173 Disk 1 sector number
     174 Disk 1 cylinder low
     175 Disk 1 cylinder high
     176 Disk 1 drive/head
     177 Disk 1 status

 1F0-1FF Fixed disk 0 (AT)
     1F0 Disk 0 data
     1F1 Disk 0 error
     1F2 Disk 0 sector count
     1F3 Disk 0 sector number
     1F4 Disk 0 cylinder low
     1F5 Disk 0 cylinder high
     1F6 Disk 0 drive/head
     1F7 Disk 0 status

 200-20F Game Adapter

 210-217 Expansion Card Ports (XT)
     210 Write: latch expansion bus data
         Read:  verify expansion bus data
     211 Write: clear wait, test latch
         Read:  MSB of data address
     212 Read:  LSB of data address
     213 Write: 0=enable, 1=/disable expansion unit
     214-215  Receiver Card Ports
     214 Write: latch data, read: data
     215 Read:  MSB of address, next read: LSB of address

     21F Reserved

 220-26F Reserved for I/O channel

 270-27F Third parallel port
     278 Data port
     279 Status port
     27A Control port

 280-2AF Reserved for I/O channel

 2A2-2A3 MSM58321RS clock

 2B0-2DF Alternate EGA, or 3270 PC video (XT, AT)

     2E0 Alternate EGA/VGA
     2E1 GPIB Adapter (AT)

 2E2-2E3 Data acquisition adapter (AT)

 2E8-2EF COM4 non PS/2 UART (Reserved by IBM)

 2F0-2F7 Reserved

 2F8-2FF COM2 Second Asynchronous Adapter

 300-31F Prototype Experimentation Card (except PCjr)

 320-32F Hard Disk Controller (XT)
     320 Read from/Write to controller
     321 Read: Controller Status, Write: controller reset
     322 Write: generate controller select pulse
     323 Write: Pattern to DMA and interrupt mask register
     324 Disk attention/status

 330-33F Reserved for XT/370

 340-35F Reserved for I/O channel

 360-36F PC Network

 370-377 Floppy disk controller (except PCjr)
     372 Diskette digital output
     374 Diskette controller status
     375 Diskette controller data
     376 Diskette controller data
     377 Diskette digital input

 378-37F Second Parallel Printer, First Parallel Printer
     378 Data port
     379 Status port
     37A Control port

 380-38F Secondary Binary Synchronous Data Link Control (SDLC) adapter
     380 On board 8255 port A, internal/external sense
     381 On board 8255 port B, external modem interface
     382 On board 8255 port C, internal control and gating
     383 On board 8255 mode register
     384 On board 8253 channel square wave generator
     385 On board 8253 channel 1 inactivity time-out
     386 On board 8253 channel 2 inactivity time-out
     387 On board 8253 mode register
     388 On board 8273 read: status; Write: Command
     389 On board 8273 write: parameter; read: response
     38A On board 8273 transmit interrupt status
     38B On board 8273 receiver interrupt status
     38C On board 8273 data

 390-39F Cluster Adapter

 3A0-3AF Primary Binary Synchronous Data Link Control (SDLC) adapter
     3A0 On board 8255 port A, internal/external sense
     3A1 On board 8255 port B, external modem interface
     3A2 On board 8255 port C, internal control and gating
     3A3 On board 8255 mode register
     3A4 On board 8253 counter 0 unused
     3A5 On board 8253 counter 1 inactivity time-outs
     3A6 On board 8253 counter 2 inactivity time-outs
     3A7 On board 8253 mode register
     3A8 On board 8251 data
     3A9 On board 8251 command/mode/status register

 3B0-3BF Monochrome Display Adapter
     3B0 Port address decodes to 3B4
     3B1 Port address decodes to 3B5
     3B2 Port address decodes to 3B4
     3B3 Port address decodes to 3B5
     3B4 6845 index register
     3B5 6845 data register [0-11h] selected by port 3B4
     3B6 Port address decodes to 3B4
     3B7 Port address decodes to 3B5
     3B8 6845 Mode control register
     3B9 Reserved for color select register on color adapter
     3BA Status register (read only)
     3BB Reserved for light pen strobe reset

 3BC-3BF Primary Parallel Printer Adapter
     3BC Parallel 1, data port
     3BD Parallel 1, status port
     3BE Parallel 1, control port

 3C0-3CF EGA/VGA
     3C0 VGA attribute and sequencer register
     3C1 Other video attributes
     3C2 EGA, VGA, CGA input status 0
     3C3 Video subsystem enable
     3C4 CGA, EGA, VGA sequencer index
     3C5 CGA, EGA, VGA sequencer
     3C6 VGA video DAC PEL mask
     3C7 VGA video DAC state
     3C8 VGA video DAC PEL address
     3C9 VGA video DAC
     3CA VGA graphics 2 position
     3CC VGA graphics 1 position
     3CD VGA feature control
     3CE VGA graphics index
     3CF Other VGA graphics

 3D0-3DF Color Graphics Monitor Adapter
     3D0 Port address decodes to 3D4
     3D1 Port address decodes to 3D5
     3D2 Port address decodes to 3D4
     3D3 Port address decodes to 3D5
     3D4 6845 index register
     3D5 6845 data register [0-11h] selected by port 3D4
     3D6 Port address decodes to 3D4
     3D7 Port address decodes to 3D5
     3D8 6845 Mode control register (CGA, EGA, VGA, except PCjr)
     3D9 Color select palette register (CGA, EGA, VGA)
     3DA Status register
     3DB Clear light pen latch
     3DC Preset Light pen latch
     3DF CRT/CPU page register (PCjr only)

 3E8-3EF COM3 non PS/2 UART (Reserved by IBM)

 3F0-3F7 Floppy disk controller (except PCjr)
     3F0 Diskette controller status A
     3F1 Diskette controller status B
     3F2 Controller control port
     3F4 Controller status register
     3F5 Data register
     3F6 Diskette controller data
     3F7 Diskette digital input

 3F8-3FF COM1 Primary Asynchronous Adapter
     3220-3227  PS/2 COM3
     3228-322F  PS/2 COM4
     4220-4227  PS/2 COM5
     4228-422F  PS/2 COM6
     5220-5227  PS/2 COM7
     5228-522F  PS/2 COM8