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© Copyright IBM Corp. 2000 47
Appendix B. 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 0000000. A
256 byte area and a 1 KB area of this RAM are reserved for BIOS data areas. Memory
can be mapped differently if POST detects an error.
Table 32. System memory map
Address range
(decimal)
Address range (hex) Size Description
0–512 KB 00000–7FFFF 512 KB Conventional
512–639 KB 80000–9FBFF 127 KB Extended conventional
639–640 KB 9FC00–9FFFF 1 KB Extended BIOS data
640–767 KB A0000–BFFFF 128 KB Dynamic video memory display
cache
768–800 KB C0000–C7FFFF 32 KB Video ROM BIOS (shadowed)
800–896 KB C8000–DFFFF 96 KB PCI space, available to adapter
ROMs
896 KB–1 MB E0000–FFFFF 128 KB System ROM BIOS (main memory
shadowed)
1–16 MB 100000–FFFFFF 15 MB PCI space
16–4096 MB 1000000–FFDFFFF 4080 MB PCI space (positive decode)
4096–4120 MB FFFE0000–FFFFFFFF 128 KB System ROM BIOS