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3 BIOS Overview
BIOS Addresses
HP I/O Port Map (I/O Addresses Used by the System
1
)
Peripheral devices, accessory devices and system controllers are
accessed via the system I/O space, which is not located in system
memory space. The 64 KB of addressable I/O space comprises 8-bit and
16-bit registers (called
I/O ports) located in the various system components. When installing
an accessory board, ensure that the I/O address space selected is in the
free area of the space reserved for accessory boards (100h to 3FFh).
Although the Setup program can be used to change some of the
settings, the following address map is not completely BIOS dependent,
but is determined partly by the operating system. Note that some of the
I/O addresses are allocated dynamically.
1. If configured.
I/O Address Ports Function
0000 - 000F DMA controller 1
0020 - 0021 Master interrupt controller (8259)
0022 - 003F Configuration registers
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 data
0072-0073 Extended CMOS
0080 Manufacturing port (POST card)
0081 - 008F DMA register
00A0 - 00A1 Slave interrupt controller
00C0 - 00DF DMA controller 2
00F0 - 00FF Co-processor
0170 - 0177 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 IDE secondary channel, secondary floppy disk drive
0378 - 037A LPT1
Applies only if a
supplementary ISA
card is installed
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