incorrect system time (4 seconds off per minute)

grabner · 24 May 2013

Hi all!

We have two computers here with the same hardware and software (see below for details), and on one of them the internal timing is incorrect by ~6%, which can be observed in many different ways:

After synchronizing the local clock with an NTP server by the command "net time /set" and waiting for exactly one minute, the local clock has advanced by 64 seconds (after some longer period of time, the clock is automatically synchronized again, so in the long run the local clock is correct, but constantly fluctuating).
The value reported by GetTickCount() (supposed to be milliseconds since system start) increases by ~64000 per minute.
The value reported by QueryPerformanceCounter() divided by the timer frequency according to QueryPerformanceFrequency() increases by 64 per minute. This is true both with and without the boot flag "useplatformclock" (i.e., using HPET and the default clock source, respectively).
The CPU clock frequency according to the registry (HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\*\~MHz) is 2921MHz (instead of 3100MHz) for all CPU cores.
The CPU clock frequency reported by the CPU-Z tool (version 1.53.1) is 2921MHz. Interestingly, newer versions of CPU-Z (up to 1.64.0), which are aware of the clock multiplier, report a frequency closer to the correct value, but still not exact.
The bus speed reported by CPU-Z is 188.48MHz (instead of 200MHz).
The peak frame rate of an external CameraLink camera connected to a Matrox frame grabber is reported by Matrox' IntelliCam tool as 144Hz (instead of 150Hz).

The CMOS clock is correct as can be observed when watching the clock in the BIOS Setup even before booting the OS. So there seems to be some very fundamental error in the time base from which the system derives many other time-related services, which are all incorrect by the same factor.

Do you have any idea which hardware component and/or system configuration entry is responsible for such behavior, and how it can be fixed?

Thanks & kind regards,
Markus

P.S.: Here are some system details:

Microsoft Windows 7 Ultimate 64-bit SP1
mainboard Supermicro H8DCL
dual AMD Opteron Processor 4234 3.1GHz
BIOS American Megatrends Inc., Version 2.0 (12/8/2011)

I think these are the relevant components, if you need more info for diagnosis, please let me know!

centaur78 · 28 May 2013

First of Please use this tool to update your profile specs for the comp that has the problem.

Second as far i can understand the CMOS RTC is losing voltage and based on bios version its almost 2 years old.

As the battery drains, output voltage drops somewhat. Lower battery voltage can impair the accuracy of the RTC. Most lithium coin cell batteries are rated at 3 V; however, actual readings on a new battery are usually higher. If your system clock seems inaccurate (it runs slow, for example like you mentioned above), check the voltage on the CMOS battery. The highest accuracy is obtained if the battery voltage is maintained at 3.0 V or higher. Lithium batteries normally maintain a fairly steady voltage until they are nearly fully discharged, whereupon the voltage quickly drops. If you check the battery voltage and find it is below 3.0 V, consider replacing the battery, even if it is before the intended replacement time

grabner · 28 May 2013

centaur78 said:

Second as far i can understand the CMOS RTC is losing voltage and based on bios version its almost 2 years old.

As the battery drains, output voltage drops somewhat. Lower battery voltage can impair the accuracy of the RTC.

Thanks for your response! As I stated above, I don't believe that the RTC is inaccurate. When I enter BIOS setup immediately after powering up the machine (i.e., before booting any OS), the correct time is displayed there and advances exactly by 60 seconds in a minute (as compared with my quartz wrist watch). Only after booting into Windows, the system time starts to drift.

If your system clock seems inaccurate (it runs slow, for example like you mentioned above)

The system clock actually runs too fast (64 seconds in one minute).

Thanks & kind regards,
Markus

centaur78 · 28 May 2013

Markus

The best way to confirm if you RTC is correct is to check the voltage of the battery

The highest accuracy is obtained if the battery voltage is maintained at 3.0 V or higher. If you check the battery voltage and find it is below 3.0 V....

Which Supermicro H8DCL model are you using ??/

grabner · 29 May 2013

centaur78 said:

The best way to confirm if you RTC is correct is to check the voltage of the battery

Well, if the RTC reports the correct time, this is fine for me, no matter what the voltage is, and since the RTC *does* report the correct time (at least in the BIOS setup page), I assume that the voltage is within the specified range. Nevertheless, can you recommend a tool to find out the CMOS battery voltage (besides opering the machine and measuring it directly)?

centaur78 said:

Which Supermicro H8DCL model are you using ??/

The "System Info" tool provided by SevenForums doesn't give much more information, it just says "Supermicro Base Board H8DCL 1234567890" (the version number is probably a fake).

Thanks & kind regards,
Markus

centaur78 · 29 May 2013

Well there is no software .... its plain old voltmeter and rolling up you sleeves.....

As with everything in life... electronic parts are prone to die someday... if you want bet your life on RTC and live with it even after 3 years of using it .....be my guest...