This chapter lists and describes system board resources.
Most Industry Standard Architecture (ISA) peripheral devices installed in the system require you to reserve an interrupt request (IRQ). Peripheral Component Interconnect (PCI) peripheral devices share system resources and can use the same IRQ. (See “PCI-to-ISA Interrupt Map” in this chapter.) At least one IRQ must be unassigned for use with your system's PCI devices.
Table 4-1. ISA Interrupt Requests
IRQ | Assignment | IRQ | Assignment |
|---|---|---|---|
0 | Reserved (timer/counter) | 8 | Reserved (real-time clock) |
1 | Reserved (keyboard controller) | 9 | System Management Bus / ACPI |
2 | Reserved (interrupt controller) | 10 | PCI |
3 | Serial ports COM 2 / COM 4 | 11 | PCI |
4 | Serial ports COM 1 / COM 3 | 12 | PS/2 mouse |
5 | PCI / Audio | 13 | Hardware Monitor |
6 | Reserved (floppy disk controller) | 14 | Primary IDE |
7 | Parallel port LPT 1 | 15 | Secondary IDE |
To reserve an IRQ for an installed peripheral device:
Start or restart the system and run the BIOS Setup program.
Go to the Advanced Screen and select the PCI Configuration parameter.
Select and reserve the appropriate IRQ.
Save the changes and exit from BIOS Setup.
The system has a limited number of available IRQs. To install more ISA peripheral devices than you have available IRQs, you must disable one unused system port for each excess ISA device, unless the device does not require an IRQ.
Some older PCI device driver software cannot share an interrupt, which is a violation of the current PCI specification. If you install a device that uses such driver software, you must free an IRQ for the device to work in the system.
PCI peripheral devices installed in the system require one or more PCI interrupt requests (PIRQ). Four interrupt lines—INTA, INTB, INTC, and INTD—are available for PCI interrupt requests.
Table 4-2. PCI-to-ISA Interrupt Map
Device | PCI Bus/Device | CF8h Value | INTA | INTB | INTC | INTD |
|---|---|---|---|---|---|---|
SCSI A | Bus 0, Dev 1, Func 0 | 800008xx | PIRQ13 |
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|
|
SCSI B | Bus 0, Dev 1, Func 1 | 800009xx |
| PIRQ12 |
|
|
Audio | Bus 0, Dev 2, Func 0 | 800010xx | PIRQ14 |
|
|
|
PCI socket 1 | Bus 0, Dev 3 | 800018xx | PIRQ00 | PIRQ01 | PIRQ02 | PIRQ03 |
PCI socket 2 | Bus 0, Dev 4 | 800020xx | PIRQ02 | PIRQ03 | PIRQ00 | PIRQ01 |
PCI socket 3 | Bus 0, Dev 5 | 800028xx | PIRQ04 | PIRQ05 | PIRQ13 | PIRQ12 |
PCI socket 6 | Bus 0, Dev 6 | 800030xx | PIRQ06 | PIRQ07 | PIRQ04 | PIRQ05 |
Ethernet | Bus 0, Dev 7, Func 0 | 800038xx | PIRQ07 |
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|
|
AGP socket | Bus 1, Dev 1 | 800100xx | PIRQ01 | PIRQ03 |
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|
PCI socket 4 | Bus 2, Dev 1 | 800208xx | PIRQ08 | PIRQ09 | PIRQ10 | PIRQ11 |
PCI socket 5 | Bus 2, Dev 2 | 800210xx | PIRQ10 | PIRQ11 | PIRQ08 | PIRQ09 |
DMA Channel | Data Width | Assignment |
|---|---|---|
0 | 8b or 16b | Open |
1 | 8b or 16b | Second choice of ECP parallel port |
2 | 8b or 16b | Floppy disk controller |
3 | 8b or 16b | First choice of ECP parallel port |
I/O Address (hex) | Assignment |
|---|---|
0000 – 000F | DMA controller 1 |
0020 – 0021 | Interrupt controller 1 |
0040 – 0043 | Timer/counter 1 |
0048 – 004B | Timer/counter 2 |
0060 | Keyboard controller |
0061 | NMI and speaker |
0064 | Keyboard controller |
0070 (bit 7) | Enable NMI |
0070 (bits 0 – 6) | RTC address (maximum 128 bytes) |
0072 – 0073 | RTC CMOS bank 2 index/data |
0080 – 008F | DMA page registers |
0092 | A20 control register |
00A0 – 00A1 | Interrupt controller 2 |
00C0 – 00DF | DMA controller 2 |
0170 – 0177 | Secondary IDE channel |
01F0 – 01F7 | Primary IDE channel |
0200 – 0207 | Audio/game port |
0220 – 022F | Audio (Sound Blaster compatible) |
0240 – 024F | Audio (Sound Blaster compatible) |
0278 – 027F | Parallel port LPT 2 |
02E8 – 02EF | Serial port COM 4 |
02F8 – 02FF | Serial port COM 2 |
0300 – 0301 | MIDI |
0330 – 0335 | MIDI |
0370 – 0375 | Floppy disk drive channel 2 |
0376 | Secondary IDE channel command |
0377 write | Floppy disk drive channel 2 command |
0377 bit 7 read | Floppy disk drive channel 2 disk change status |
0377 bits 0 – 6 | Secondary IDE channel status |
0378 – 037F | Parallel port LPT 1 |
03B4 – 03B5 | Add-in card; VGA |
03BA | Add-in card; VGA |
03BC – 03BF | Parallel port LPT 3 |
03C0 – 03CA | Add-in card; VGA |
03CC | Add-in card; VGA |
03CE – 03CF | Add-in card; VGA |
03D4 – 03D5 | Add-in card; VGA |
03DA | Add-in card; VGA |
03E8 – 03EF | Serial port COM 3 |
03F0 – 03F5 | Floppy disk drive channel 1 |
03F6 | Primary IDE channel command |
03F7 write | Floppy disk drive channel 1 command |
03F7 bit 7 read | Floppy disk drive channel 1 disk change status |
03F7 bits 0 – 6 | Primary IDE channel status |
03F8 – 03FF | Serial port COM 1 |
040B | DMA ext. write mode register |
04D0 – 04D1 | Edge/level interrupt control register |
04D6 | DMA ext. write mode register |
0500 – 050F | SMBus control registers |
0510 – 055F | ACPI registers |
0C00 – 0C01 | PCI-to-IRQ mapping registers |
0C06 – 0C08 | Security registers |
0C14 | PCI error status register |
0C49 – 0C4A | Rise-time counter register |
0C50 – 0C52 | General-purpose registers |
0C6C – 0C6F | ISA control registers |
0CD6 – 0CD7 | Power management registers |
0CF8 – 0CFB | PCI configuration address registers (DW access) |
0CFC – 0CFF | PCI configuration data registers |
0F50 – 0F58 | General-purpose chip select |
Memory Address | Range | Description |
|---|---|---|
0 K–640 K | 00000000 – 0009FFFF | DOS conventional memory |
640 K–768 K | 000A0000 – 000BFFFF | VGA memory and BIOS |
768 K–896 K | 000C0000 – 000DFFFF | Expansion card BIOS and buffer |
896 K–1024 K | 000E0000 – 000FFFFF | System BIOS |
1024 K–Top of memory | 00100000 – Top of memory | Main memory |
(4 G–20 M) – (4 G–19 M) | FEC00000 – FECFFFFF | APIC configuration space |
(4 G–18 M) – (4 G–17 M) | FEE00000 – FEEFFFFF | APIC configuration space |
(4 G–4 M) – 4 G | FFC00000 – FFFFFFFF | High system BIOS |
4 G–8 G |
| Maximum allowable memory |