IBM BDM-610000049 user manual First Megabyte Memory Map

Memory Map

Table 41 shows how memory in the first megabyte is allocated in the system.

	Table 41 First Megabyte Memory Map
Address (hex)	Description
C0000–FFFFFh ROM	256 KB BIOS in Flash EPROM, shadowed into DRAM during runtime.
C0000–EFFFFh	Run time user memory space. Usually, memory between C0000h and CFFFFh
	is used for the BIOS of add-on VGA video cards.
A0000–BFFFFh	Normally used for video RAM as follows:
	EGA/VGA	0A0000–0AFFFFh
	Monochrome	0B0000–0B7FFFh
	CGA	0B8000–0BFFFFh
00502–9FFFFh	DOS reserved memory area
00400–00501h	BIOS data area
00000–003FFh	Interrupt vector area

Memory beyond the first megabyte can be accessed in real mode by using EMS or a similar memory manager. See your OS or programming language references for information on memory managers.

BDM-610000049 Rev G Chapter 4: Using the cpuModule 59