IBM 3708 Description page 59

Time Stamps and Error Log Entries
The time indicated on the relative time clock is used to create the time stamps that
are a part of each error log entry, allowing a customer to determine the relative time
of certain events.
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At each power on of the 3708, the error log, alert log, and relative time clock areas
of EEPROM are copied to RAM. The RAM versions are then updated as the 3708
operates. Every 4 hours, the RAM versions are copied back to EEPROM, if any
changes have occurred. (Because of this copy function, it is possible to lose up to 4
hours of entries in the error and alert logs when the 3708 is powered off or restarted.
The RAM copies are lost at each restart.)
At power on, or restart, a special error log entry is created as follows using the last
relative time clock value that was saved in EEPROM.
00 00 FE FE FE FE FE FE TTTT TTTT
TTTT TTTT is the relative time clock value.
After creating this entry, the day count of the relative time clock is incremented by
1, and the 45-minute count and the quarter second timer are reset to O. For
example, if the 3708 is powered off and back on, the restart error log entry might
look like:
00 00 FE FE FE FE FE FE 1980 0126
The 19800126 would have been the last clock value saved in EEPROM on the
previous power on. After the entry is created, the clock is set to the value 19AO
0000 (day count incremented by I, and 45 minute and quarter second counters
set to 0).
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IBM 3708 Description