Windows 8 overclock-related RTC bug isolated and fixed

By on August 26, 2013, 7:30 PM

Last week, a bug was discovered in Windows 8 that affects the real-time clock while overclocking, causing inaccurate benchmark results. This discovery prompted popular overclocking leaderboards site HWBOT to ban Windows 8 results from both Intel and AMD systems, as overclockers could use the bug to unfairly enhance their score.

Ocaholic's Christian Ney teamed up with CPU-Z author Franck Delattre to try and isolate the cause of the issue, using a utility that read four system timers (QPC, HPET, ACPI and the problematic RTC) in real time. At the default bus frequency of 100 MHz on an Intel-based system, each of the four clocks had the same readout, but when the bus frequency was adjusted down to 95 MHz from within Windows 8, the readout from the RTC and QPC clocks went off the rails.

Further exploration of the issue revealed that if you change the CPU frequency in the BIOS, the clocks are unaffected on boot-up, and although AMD systems are largely fine, the bug can cause issues in some circumstances. The team also confirmed that Windows 8 is the only operating system affected by the bug due to changes in the RTC's time sourcing methods.

Importantly, the bug can be fixed through a simple command line prompt. However, as the RTC is still very easy to fool in Windows 8, and it can't be guaranteed that all overclockers will apply the fix, Ocaholic believes that Windows 8 benchmarking results still can't be trusted.

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