Specifications

EPC-8 Hardware Reference
4 4
4-4
Memory at addresses between 0 and 1 MB (0FFFFFh) is mapped as follows:
Range Content
000000 - 09FFFF DRAM (first 640 KB)
0A0000 - 0BFFFF Almost always used by a video controller as
video RAM.
If the onboard VGA is populated and
enabled, then this memory is
accessed over the CPU local bus. Otherwise,
it is mapped to the EXM interface.
0C0000 - 0C7FFF Write-protected DRAM containing video
BIOS
0C8000 - 0DFFFF* Uncommitted; mapped to EXM interface.
0E0000 - 0EFFFF Either is mapped to EXM interface or is
window into the VMEbus. Mapping
controlled by bit-1 of register 8102.
0F0000 - 0FFFFF Write-protected DRAM containing system
BIOS
* 0C8000 - 0DFFFF may be used either as page frames (i.e. for Ethernet, etc.) or
may be used by DOS as upper memory blocks if an EMM driver is installed or
may be used for BIOS extensions.
For a 4 MB EPC-8, the extended memory address space is defined as follows:
00100000 003FFFFF 3 Mbytes DRAM extended memory
00400000 00FFFFFF Uncommitted; mapped to EXM interface
For an 8 MB EPC-8, the extended memory address space is defined as follows:
00100000 007FFFFF 7 Mbytes DRAM extended memory
00800000 00FFFFFF Uncommitted; mapped to EXM interface
For a 16 MB EPC-8, the extended memory address space is defined as follows:
00100000 00FFFFFF 15 Mbytes DRAM extended memory
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