Appendix C. System Address Maps; System Memory Map; I/O Address Map - IBM NetVista A21 User Manual

Appendix C. System address maps

The following charts represent how the hard disk stores different types of
information. Address ranges and byte sizes are approximate.

System memory map

The first 640 KB of system board RAM is mapped starting at address hex
00000000. A 256-byte area and a 1 KB area of this RAM are reserved for BIOS
data. Memory can be mapped differently if POST detects an error.
Table 1. System memory map
Address range Address range (hex)
(decimal)
0 K – 512 KB 00000 – 7FFFF
512 K – 639 KB 80000 – 9FBFF
639 K – 640 KB 9FC00 – 9FFFF
640 K – 767 KB A0000 – BFFFF
768 K – 800 KB C0000 – C7FFF
800 K – 896 KB C8000 – DFFFF
896 K – 1 MB E0000 – FFFFF
1 MB – 16 MB 1000000 – FFFFFF
16 MB – 4096 MB 10000000 – FFDFFFFF
FFFE0000 – FFFFFFFF

I/O address map

The following table lists resource assignments for the I/O address map. Any
addresses that are not shown are reserved.
Table 2. I/O address map
Address range (hex)
0000 – 000F
0010 – 001F
0020 – 0021
0022 – 003F
0040 – 0043
0044 – 00FF
0060
0061
0064
0070, bit 7
0070, bits 6:0
0071
0072
© Copyright IBM Corp. 2001
Size
512 KB
127 KB
1 KB
128 KB
32 KB
96 KB
128 KB
15 MB
4080 MB
128 KB
Size (bytes) Description
16 DMA 1
16 General I/O locations, available to PCI bus
2 Interrupt controller 1
30 General I/O locations, available to PCI bus
4 Counter/timer 1
28 General I/O locations, available to PCI bus
1 Keyboard controller byte, reset IRQ
1 System port B
1 Keyboard controller, CMD/ATAT byte
1 bit Enable NMI
6 bits Real-time clock, address
1 Real-time clock, data
1 bit Enable NMI
Description
Conventional
Extended conventional
Extended BIOS data
Dynamic video memory display cache
Video ROM BIOS (shadowed)
PCI space, available to adapter ROMs
System ROM BIOS (main memory shadowed)
PCI space
PCI space (positive decode)
System ROM BIOS
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