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System Board
3.4
SYSTEM MEMORY
General
The system board contains:
•
128 Kbytes of ROM.
•
system RAM.
•
50 byte battery backed Real-time clock CMOS RAM.
•
expansion ROM socket (optional).
Read only memory (ROM)
The system ROM contains the BIOS and the system board Setup utility. It
consists of a 1 Mbit EPROM arranged as 128 Kbytes of memory. It is addressed
at the top of the first and last Megabyte of the processor address space and is
not parity checked.
The lower 64 Kbytes of the ROM contains code which is used only during the
boot process. If shadow RAM is enabled this lower 64 Kbyte address space
(E0000-EFFFF) is available for use as RAM. If shadowing is disabled the top 128
Kbytes of the first and last Mbytes are used by the system ROM.
Random access memory (RAM)
Four Megabytes of RAM are soldered directly to the system board. Additional
RAM is plugged into SIMM sockets on the system board. Upgrades are in pairs
of 1 or 4 Mbyte SIMMs giving upgrade capacities of 2 and 8 Mbytes. The
following table gives the permissible upgrade combinations and the total system
RAM available with each.
System board
capacity (Mbytes)
Note
When banks 2 and 3 are both occupied by 8 Mbyte upgrades the RAM soldered to the system
board is disabled.
3/10 LS PRO HARDWARE TECHNICAL REFERENCE
Upgrade to
(Mbytes)
4
6
4
8
4
12
4
16
Bank
(Mbytes)
1
2
3
N/A
2
-
N/A
2
2
N/A
8
-
N/A
8
8
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