System BIOS
BIOS Addresses
Chapter 3
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system components. When you install an accessory board, ensure that the selected I/O
address space is in the free area of the space reserved for accessory boards (100h to
3FFh).
DMA Channel Controllers
The system permits only I/O-to-memory and memory-to-I/O transfers. The hardware
configuration doesn’t allow I/O-to-I/O or memory-to-memory transfers.
The system controller supports seven DMA channels, each with a page register that
extends the channel’s addressing range to 16MB.
Default Values for
I/O Address Ports
Function
0000 - 0CF7 DMA controller 1
0020 - 0021 Master interrupt controller (8259)
002E - 002F Super I/O
0040 - 0043 Timer 1
0060, 0064 Keyboard controller (reset, slow A20)
0061 Port B (speaker, NMI status, and control)
0070 Bit 7: NMI mask register
0070 - 0071 RTC and CMOS
0080 Manufacturing port (POST card)
0081 - 0083, 008F DMA low page register
0092 PS/2 reset and Fast A20
00A0 - 00A1 Slave interrupt controller
00C0 - 00DF DMA controller 2
00F0 - 00FF Coprocessor error
0170 - 0177 Free (IDE secondary channel)
01F0 - 01F7 IDE primary channel
0278 - 027F LPT 2
02E8 - 02EF Serial port 4 (COM4)
02F8 - 02FF Serial port 2 (COM2)
0372 - 0377 Free (IDE secondary channel, secondary floppy disk
drive)
0378 - 037F LPT1
03B0 - 03DF VGA
03E8 - 03EF COM3
03F0 - 03F5 Floppy disk drive controller
03F6 IDE primary channel
03F7 Floppy disk drive controller
03F8 - 03FF COM1
04D0 - 04D1 Interrupt edge/level control
0778 - 077F LPT1 ECP
0CF8 - 0CFF PCI configuration space
C000 - Power management I/O space and ACPI registers
C100 - C10F SMBus I/O space
