Typical device DMA Channels

PC/XT Device Addresses

DMA Channels

irq Assignments


Typical device DMA channels
Device type
Typical dma
SCSI 3,5
Sound Card 1,5,7
Network Card 1,3,5,7

PC/XT Device Addresses
I/O Address
000-01Fh DMA Controller - Channels 0-3
020h-021h Interrupt Controllers
040-043h System Timers
060h Keyboard, Aux.
070h-071h Real Time Clock / CMOS, NMI Mask
081-083h & 087h DMA Page Register (0-3)
0F0-0FFh Math Coprocessor
108-12Fh Not Assigned; Reserved by/for IBM use
130-13Fh Not Assigned; Reserved by/for IBM use
140-14Fh Not Assigned; Reserved by/for IBM use
150-1Efh Not Assigned; Reserved by/for IBM use
200-207h Game Port
208-20Bh Not Assigned
20C-20Dh Reserved
20E-21E Not Assigned
21F Reserved
220-22xh Not Assigned
230-23xh Not Assigned
240-247h Not Assigned
250-277h Not Assigned
278-27Fh LPT 2 or LPT 3 -- 3rd Parallel I/O Port
280-2Afh Not Assigned
2B0-2Dfh Alternative EGA Port
2E1h GPIB 0
2E2h & 2E3h Data Acq 0
2E4--2E7h Not Assigned
2E8-2Efh COM 4 -- 4th Serial I/O Port
2F8-2FFh COM 2 -- 2nd Serial I/O Port
300-31Fh IBM Prototype Card
320-323h Primary PC/XT Hard Disk Adapter
324-327h Secondary PC/XT Hard Disk Adapter
328-32Fh Not Assigned
330-33Fh Not Assigned
340-34Fh Not Assigned
350-35Fh Not Assigned
360-363h PC Network Card -- Low I/O Port
364-367h Reserved
368-36Ah PC Network Card -- HighI/O Port
36C-36Fh Reserved
370-377h Secondary Diskette Drive Adapter
378-37Fh LPT 2 or LPT 1 -- 1st or 2nd Parallel I/O Port
380-389h Not Assigned
380-38Ch BISYNC_1 or SDLC_2
390-393h Cluster Adapter
394-3A9h Not Assigned
3A0-3ACh BISYNC_2 or SDLC_1
3B0-3BFh Monochrome Video Adapter
3BC-3BFh 1st Parallel I/O Port -- Part of Monochrome Video Card
3C0-3CFh EGA Video
3D0-3DFh CGA Video
3E0-3E7h Not Assigned
3E8-3EFh COM3 -- 3rd Serial I/O Port
3F0-3F7h Primary Diskette Drive Adapter
3F8-3FFh COM1 -- 1st Serial I/O Port

DMA Channels
BIOS Address
C000-C7FF Color video adapters (32k)
C800-CFFF Hard disk controller or SCSI (32k)
C800-CFFF SCSI Host Adapter BIOS (32k)
D000-D7FF SCSI Host Adapter BIOS (32k)
D800-DFFF SCSI Host Adapter BIOS (32k)
E000-E7FF SCSI Host Adapter BIOS (32k)
E800-EFFF SCSI Host Adapter BIOS (32k)
E000-EFFF LIMS EMS Memory Page Frame (64k)

IRO Assignments
AT's on up
0 System Timer System Timer
1 Keyboard Controller Keyboard Controller
2 Not Assigned Tied to IRQs 8-15
3 COM2 : 2F8h-2FFh COM2: 2F8h-2FFh
4 COM1: 3F8h-3FFh COM1: 3F8h-3FFh
5 XT HD Controller LPT2: 378h or 278h
6 Diskette Controller Diskette Controller
7 LPT1: 3BCh or 378H LPT1: 3BCh or 378h
8 Not Avalible on PC or XT Real Time Clock
9 Not Avalible on PC or XT Substutes for IRQ 2
10 Not Avalible on PC or XT Not Assigned
11 Not Avalible on PC or XT Not Assigned
12 Not Avalible on PC or XT PS/2 Mouse Port
13 Not Avalible on PC or XT NPU (Math Coprocessor)
14 Not Avalible on PC or XT Hard Disk
15 Not Avalible on PC or XT 2nd Hard Disk Adapter