Microsoft KB Archive/946033

= The system time may differ from the BIOS time on a Windows Vista-based computer that supports High Precision Event Timer =

Article ID: 946033

Article Last Modified on 12/14/2007

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APPLIES TO


 * Windows Vista Enterprise 64-bit Edition
 * Windows Vista Home Basic 64-bit Edition
 * Windows Vista Home Premium 64-bit Edition
 * Windows Vista Ultimate 64-bit Edition
 * Windows Vista Business
 * Windows Vista Business 64-bit Edition
 * Windows Vista Enterprise
 * Windows Vista Home Basic
 * Windows Vista Home Premium
 * Windows Vista Ultimate

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SUMMARY
You use a Windows Vista-based computer that supports High Precision Event Timer (HPET), and the computer runs for several hours. Then, you may notice that the system time differs from the BIOS time by several seconds.



MORE INFORMATION
This time difference occurs because the HPET hardware and the Real-Time Clock (RTC) are never completely accurate. The W32Time service synchronizes the system time with a Network Time Protocol (NTP) server to account for any time differences. If there is no active connection to an NTP server, the system time is synchronized with the BIOS clock. If the time difference exceeds 60 seconds, the system time is corrected automatically according to the BIOS clock.

Keywords: kbhowto kbinfo kb3rdpartyhardware KB946033

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