Operations - IBM 5170 Technical Reference

0600H 1536Kb I/O adapter
to
3COOH
15360Kb I/O adapter (15Mb
maximum)
Note: This word reflects the total expansion memory above
the 1Mb address space as determined at power-on time. This
expansion memory size can be determined through system
interrupt 15 (see the BIOS listing). The base memory at
power-on time is determined through the system
memory-size-determine interrupt.
Date Century Byte (Hex 32)
Bit 7-Bit 0 BCD value for the century (BIOS interface to
read and set).
Information Flag (Hex 33)
Bit 7
Set if the IBM Personal Computer AT 128KB
Memory Expansion Option is installed.
Bit 6 This bit is used by the Setup utility to put out a
first user message after initial setup.
Bit 5-Bit 0 Reserved
Note: Hex addresses 34 through 3F are reserved.
110 Operations
Writing to CMOS RAM involves two steps:
1. OUT to port hex 70 with the CMOS address that will be
written to.
2. OUT to port hex 71 with the data to be written.
1-54 System Board