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Chapter 3 Hardware
XTX 820 Reference Manual 17
Table 3-1. Interrupt Channel Assignments (IRQs)
IRQ# Available Typical Interrupt Source Connected to Pin
0 No Counter 0 NA
1 No Keyboard NA
2 No Cascade Interrupt from Slave PIC NA
3 Note 1 Serial Port 2 (COM2) / Generic IRQ3 via SERIRQ
4 Note 1 Serial Port 1 (COM1) / Generic IRQ4 via SERIRQ
5 Note 2 Parallel Port 2 (LPT2) / Generic IRQ5 via SERIRQ
6 Note 1 Floppy Drive Controller / Generic IRQ6 via SERIRQ
7 Note 1 Parallel Port 1 (LPT1) / Generic IRQ7 via SERIRQ
8 No Real-time Clock NA
9 Note 4 SCI / Generic IRQ9 via SERIRQ
10 Note 2, 1 Serial Port 3 (COM3) / Generic IRQ10 via SERIRQ
11 Note 2, 1 Serial Port 4 (COM4) / Generic IRQ11 via SERIRQ
12 Note 1 PS/2 Mouse / Generic IRQ12 via SERIRQ
13 No Math processor NA
14 Note 1, 3 IDE Controller 0 (IDE0) / Generic IRQ14
15 Note 1, 3 IDE Controller 1 (IDE1) / Generic IRQ15
Notes: In PIC mode, the PCI bus interrupt lines can be routed to any free IRQ.
1. Default, but can be changed to another interrupt. If disabled in BIOS Setup, the interrupt can
be used for another purpose.
2. Function described is available if the baseboard is equipped with the Super I/O controller
Winbond (W83627HG). This I/O controller is supported by the XTX 820 Embedded BIOS.
3. If the ATA/IDE configuration is set to enhanced mode in BIOS setup (serial ATA and
parallel ATA native mode operation), IRQ14 and 15 are free for PCI/LPC bus.
4. In ACPI mode, IRQ9 is used for the SCI (System Control Interrupt). The SCI can be shared
with a PCI interrupt line.
Memory Map
The following table provides the common PC/AT memory allocations. Memory below 000500h is used
by the BIOS.
Table 3-2. Memory Map
Address Range
(decimal)
Address Range
(hex)
Size Description
(TOM-192kB) to TOM NA 192 kB ACPI reclaim, MPS and NVS area **
(TOM-8MB-192kB) to
(TOM-192kB)
NA 1 or 8 MB VGA frame buffer *
1024 k to (TOM- 8MB
-192kB)
100000 - N.A NA Extended memory
869 k - 1024 k E0000 - FFFFF 128 kB Runtime BIOS
800 k - 869 k CC000 - DFFFF 96 kB Upper memory
640 k - 800 k A0000 - CBFFF 160 kB Video memory and Video BIOS