IBM PC 100, Technical Manual

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Chapter 1. System Description
System Address Maps
Memory Map
The first 640 KB of system board RAM is mapped starting at address 0000000h. 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. See the section about BIOS data areas in the
IBM Personal System/2 and Personal
Computer BIOS Interface Technical Reference for details.
Input/Output Address Map
The following figures list the system board I/O address maps. Any addresses that are not shown are
reserved.
Figure 3. System Memory Map
Address Range
(Decimal) Address Range
(Hex) Size Description
1024K–131072K 100000–8000000 127M Extended memory
960K–1023K F0000–FFFFF 64K System BIOS
944K–959K EC000–EFFFF 16K Available
936K–943K EA000–EBFFF 8K ESCD (Plug and Play configuration area)
928K–935K E8000-E9FFF 8K Available
896K–927K E0000–E7FFF 32K BIOS reserved
800K–895K C8000–DFFFF 96K Available HI DOS memory (open to ISA and PCI bus)
640K–799K A0000–C7FFF 160K Video memory and BIOS
512K–639K 80000–9FFFF 128K Extended
0K–511K 00000–7FFFF 512K DOS applications (conventional)
Figure 4 (Page 1 of 3). I/O Address Map
Address (Hex) Device
0000–000F DMA 1
0020–003F Interrupt controller 1
0040–0043 Timer 1
0044–0047 Available I/O for ISA/PCI bus
0048–004B Timer 2
004C–005F Available I/O for ISA/PCI bus
0060 Keyboard controller data byte
0061 System Port B
0062–0063 Available I/O for ISA/PCI bus
0064 Keyboard controller, command and status byte
0065–006F Available I/O for ISA/PCI bus
0070, bit 7 Enable/disable NMI
0070, bits 6:0 Real time clock address
0071 Real time clock data
0072–0077 Available I/O for ISA/PCI bus
0078 Reserved-system board setup
0079 Reserved-system board setup
007A–007F Available I/O for ISA/PCI bus
0080 POST checkpoint register
0080-008F DMA page register
0090–009F Available I/O for ISA/PCI bus
00A0–00BF Interrupt controller 2
00C0–00DE DMA 2
00DF–00EF Available I/O for ISA/PCI bus
Chapter 1. System Description
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