IBM Partner Pavilion 6791, 6343 Appendix C. System address maps, System memory map, Address map

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)	Size		Description
(decimal)
0 K – 512 KB		00000 – 7FFFF	512 KB		Conventional
512	K – 639 KB	80000 – 9FBFF	127 KB		Extended conventional
639	K – 640 KB	9FC00 – 9FFFF	1 KB		Extended BIOS data
640	K – 767 KB	A0000 – BFFFF	128 KB		Dynamic video memory display cache
768	K – 800 KB	C0000 – C7FFF	32	KB	Video ROM BIOS (shadowed)
800	K – 896 KB	C8000 – DFFFF	96	KB	PCI space, available to adapter ROMs
896	K – 1 MB	E0000 – FFFFF	128 KB		System ROM BIOS (main memory shadowed)
1 MB – 16 MB		1000000 – FFFFFF	15	MB	PCI space
16 MB – 4096 MB		10000000 – FFDFFFFF	4080 MB		PCI space (positive decode)
		FFFE0000 – FFFFFFFF	128 KB		System ROM BIOS

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)		Size (bytes)	Description
0000	– 000F	16	DMA 1
0010	– 001F	16	General I/O locations, available to PCI bus
0020	– 0021	2	Interrupt controller 1
0022	– 003F	30	General I/O locations, available to PCI bus
0040	– 0043	4	Counter/timer 1
0044	– 00FF	28	General I/O locations, available to PCI bus
0060		1	Keyboard controller byte, reset IRQ
0061		1	System port B
0064		1	Keyboard controller, CMD/ATAT byte
0070, bit 7		1 bit	Enable NMI
0070, bits 6:0		6 bits	Real-time clock, address
0071		1	Real-time clock, data

© Copyright IBM Corp. 2001 63