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3
EPC-26A/27 Hardware Reference
Memory Expansion
A single 72-pin SIMM socket is provided for memory expansion. A standard SIMM
module is used for expansion, and must meet the following criteria:
- 3.3 Volt
- fast page mode
- 72-pin
3
- 70 nanosecond DRAM or better
- single-sided or double-sided
There are four different 72-pin SIMM modules that can be installed into the SIMM
socket. The different sizes available are 4, 8, 16 and 32 MBytes.
Memory Map
The Intel DX2/DX4 SL Enhanced CPU supports a 32-bit physical memory address.
Memory at addresses between 0 and 32 MB is mapped as follows:
Range
0000000 - 009FFFFh
00A0000 - 00BFFFFh
00C0000 - 00C7FFFh
00C8000 - 00DFFFFh
00E0000 - 00EFFFF
00F0000 - 00FFFFFh
0100000 - 13FFFFFh
1400000 - 1FEFFFFh
1FF0000 - 1FFFFFFh
0C8000 - 0EFFFF may be used either as page frame, BIOS extension, I/O buffer
(i.e. for extended memory managers, Ethernet, etc.) or may be used by DOS as upper
memory blocks if an extended memory manager driver is installed.
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Content
DRAM (first 640 KB)
Mapped to EXM expansion interface; almost always
used by a video controller as video RAM
Shadowed video BIOS (if video is used)
(write protected)
Mapped to EXM expansion interface
System Upper Memory
Write-protected DRAM containing BIOS
Extended memory when installed or mapped to EXM
expansion interface
Mapped to EXM expansion interface
Mapped to BIOS ROM
Table 3-2. Memory Map.
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