Published in Processors

Windows 8 RTC bug isolated, fixed

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Workaround exists


As you may already know, HWBot recently banned all benchmark submissions from systems running Windows 8 due to an issue with the correct real-time clock (RTC) and how it behaves when the system is underclocked or overclocked. The issue was more likely to happen on Intel- rather than AMD-based systems, so HWBot decided to exclude AMD from the list. Well known overclocker Christian Ney further investigated the issue and actully found the underlying source of the bug as well as a fix for it.

In a cooperation with Franck Delattre, the guy behind CPU-Z, which reads four system timers in real-time (ACPI, HPET, RTC, and QPC) and how the actual DMI frequency (BCLK on Intel and HTT on AMD) is calculated based on each timer, they managed to find the actual problem and conclude that the system is not affected when the frequency is set via BIOS and forced to boot on that frequency but rather only when it is set "on-the-fly". This also means that Windows 8 does not actually use ACPI or HPET as previously thought but rather an internal timer.

Although it was suspected that AMD-based systems are excluded from the issue, it appears that they are also affected albeit with much less consenquences due to the fact that Windows 8 automatically set/add the "useplatformclock" parameter to "yes" after the second boot.

The fix for the issue is quite simple as it only requires to run the "bcdedit /set {current} useplatformclock Yes" in command prompt as admin. Of course, HWBot now needs to find a way to confirm if the system is running with the correct RTC.

More here.




Last modified on 27 August 2013
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