IBM 770 manual System Memory Map, System Board

System Memory Map

Memory is mapped by the memory controller registers.

Figure 2-10 on page 2-17 shows the memory map for a correctly functioning system. Memory can be mapped differently if POST detects an error in system board memory or RT/CMOS RAM. In the figure, the variablex represents the number of 1 MB blocks of

system board memory starting at or above the hex 100000 boundary.

Hex Address		Range	Function
00000000	to	0009FFFF	640 KB system board RAM
000A0000	to	000BFFFF	Video		RAM
000C0000	to	000C9FFF	System		board	video	BIOS ROM mapped	to
			RAM
000C8000	to	000EFFFF	Channel		ROM
000F0000	to	000FFFFF	64	KB	system board ROM mapped to			RAM
00100000	to	(00100000 + x	x	MB	system	board	RAM
MB)
FFFF0000	to	FFFFFFFF	64 KB system board ROM
			(same as			000F0000 to	000FFFFF)

Figure 2-10. System Memory Map

System Board 2-17