Lenovo ThinkPad 600E Technical Reference Manual for the ThinkPad 600 - Page 40

RT/CMOS RAM The RT/CMOS RAM (real-time clock/complementary metal-oxide semiconductor RAM) module contains the real-time clock and 128 bytes of CMOS RAM. The clock circuitry uses 14 bytes of this memory; the remainder is allocated to configuration and system-status information. A battery is built into the module to keep the RT/CMOS RAM active when the power supply is not turned on. In addition to the 128 bytes of CMOS/RAM, a CMOS/RAM extension of 4 KB is provided for configuration and other system information. Figure 2-13 lists the RT/CMOS RAM bytes and their addresses. Address (Hex) 000-00D 00E 00F 010 011 012 013 014 015, 016 017, 018 019 01A 01B 01C 01D-02D 02E, 02F 030, 031 032 033-07F RT/CMOS RAM Bytes Real-time clock Diagnostic status Shutdown status Diskette drive type Hard disk 2 and 3 drive type Hard disk 0 and 1 drive type Reserved Equipment Low and high base memory Low and high expansion memory Hard disk 0 extended byte Hard disk 1 extended byte Hard disk 2 extended byte Hard disk 3 extended byte Reserved Checksum Low and high usable memory above 1 MB Date-century Reserved Figure 2-13. RT/CMOS RAM Address Map 2-18 System Board