Appendix C.system Address Maps; System Memory Map; I/O Address Map - IBM Netvista A20i User Manual

System memory map

I/O address map

The following charts represent how the hard disk stores different types of information. Address
ranges and byte sizes are approximate.
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
(decimal)
0~640 KB
640~768 KB
768~816 KB
816~896 KB
896~960 KB
960~1024 KB
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 (hex)
000-00F
0020 – 0021
0022 – 003F
040-043
060-060
061-061
070-071
081-08F
0A0-0A1
Address range (hex)
(000000 ~ 09FFFF)
(0A0000 ~ 0BFFFF)
(0C0000 ~ CBFFFF)
(0CC000 ~ 0DFFFF)
(0E0000 ~ 0EFFFF)
(0F0000 ~ 0FFFFF)
(100000 ~ Upper Limit)
(Upper Limit ~ 4 GB)
DMA controller-1
Interrupt controller 1
General I/0 locations, available to PCI bus
System timer
Keyboard controller 8742
System Speaker
CMOS RAM Address and Real Time Clock
DMA controller-2
Interrupt controller-2
Description
Main memory
VGA memory
Video BIOS Memory
ISA Card BIOS & Buffer Memory
BIOS Extension Memory
Setup and Post Memory
PCI Development BIOS
System BIOS memory
Main memory
PCI memory
Description
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