Specifications

PC/II+p Board Technical Reference Manual 80
MT002615 ©1999-2001, Megatel Computer Corporation
8.2 Memory Map – First Megabyte
A total of up to 64 Megabytes of main memory can be shipped on-board. The mapping of memory in the first
megabyte of main memory (A.K.A. real-mode memory) is given in Table 42
, below.
Table 42 Memory Map – First Megabyte
MEMORY ADDRESS
REGION
1
LENGTH DESCRIPTION
0x00000000 – 0x0009FFFF
640 KB Base Memory Address Region.
0x000A0000 – 0x000AFFFF
64 KB Video 69030 – VGA Frame Buffer
0x000B0000 – 0x000B7FFF
32 KB Video 69030 – MDA Emulation Character Buffer
0x000B8000 – 0x000BFFFF
32 KB Video 69030 – CGA Emulation Frame Buffer
0x000C0000 – 0x000CFFFF
64 KB
Option BIOS Memory Address Region. This memory
address region is ALWAYS shadowed. All memory
accesses to this region are always forwarded to
system memory, never to the system bus. This region
typically contains the VGA BIOS.
0x000D0000 – 0x000DFFFF
64 KB Reserved.
0x000E0000 – 0x000E7FFF
32 KB Reserved.
0x000E8000 – 0x000EFFFF
32 KB
Flash Disk Memory Address Region. This memory
address region is used to access the Flash Disk, and
it can be shadowed with system memory when access
to Flash Disk is not required. Memory accesses are
forwarded to the system bus, causing X32CS# (Flash
Disk Chip Select) to be asserted only if X32CS# is
enabled.
0x000F0000 – 0x000FFFFF
64 KB
BIOS ROM Memory Address Region. This memory
address region is used for standard BIOS ROM.
Memory write accesses to this address region are
always forwarded to system memory, never to the
system bus. Memory read accesses to this address
region are forwarded to the system bus, only if
enabled, otherwise they are forwarded to system
memory.
NOTES
(1) Addresses are expressed in hexadecimal notation; all addresses are in the first 1MB of physical address
space (also known as 'real memory' address region).