In an odd turn of events, Windows 8 has been banned from HWBot, one of the world’s top benchmarking and overclocking communities. All existing benchmarks recorded by Windows 8 have been disqualified. This is due to a fault in Windows 8’s real-time clock (RTC), which all benchmarking tools use as a baseline.

HWBot is a massive online database of benchmark records, covering most of the major benchmarking tools, such as 3DMark, PCMark, and SuperPi. Users submit their benchmarks, moderators check their results, and then people are awarded points or trophies depending on how they rank. It’s a useful site for seeing how your system/components compare against other setups, but also — as always with such sites — there’s a large number of enthusiast overclockers who rule the charts. Some people take it very seriously: Andre Yang, one of the world’s best overclockers, currently holds the record for the highest CPU frequency (8709 MHz with an AMD FX-8150) and the highest 3D Mark 11 score (37263, with four Nvidia GTX Titans).

In almost every modern computer, there’s a real-time clock (RTC) that keeps accurate track of the time even when the computer is turned off. Usually this is done through some kind of package on the main logic board that just sits there, quietly ticking away the seconds. In modern computers, the RTC is often built into the southbridge. In standalone RTCs, the package usually contains a built-in power source (a battery) that keeps the RTC going, so that the device still shows the right time after experiencing a power cut or being relocated; in the case of your PC, there’s probably a button battery or supercapacitor on the motherboard that keeps the southbridge powered. (As for why your microwave doesn’t contain an RTC to prevent that the Blinking Clock of Doom, who knows…)

The RTC, due to its implemented-in-hardware nature, is very useful for providing a baseline for benchmarks. Unlike software, which can be easily meddled with or affected by outside influences, the RTC in your PC — as the name suggests — is designed to keep pace with real-world time. For every second that ticks by on your quartz-powered wristwatch, a second ticks by inside your PC. Thus, to generate accurate results, benchmarking tools use the RTC to work out exactly when the benchmark started and finished. This is how most benchmarks have always operated, and it’s how every major benchmark operates today.

Unfortunately, though, Windows 8’s RTC isn’t reliable. According to HWBot, Microsoft made some changes to Windows 8’s timekeeping routines to allow for low-cost devices and embedded systems that don’t always have a conventional PC-compatible RTC. HWBot doesn’t give specific details (presumably we’re talking really low-level kernel stuff here), but it proves its point with some damning empirical evidence. Basically, if you change your CPU base clock (BCLK) frequency in software (not at boot time), it has a massive impact on Windows 8’s ability to keep accurate time. By underclocking the BLCK of a Haswell system from 130MHz to 122MHz (-6%), Windows 8 loses 18 seconds over a five minute period (see video above); and the inverse applies to overclocking, too.

Of course, this might be a big deal and it might not.

This is a problem for benchmarks, because they trust your RTC implicitly — they assume that your system is still keeping accurate time, when in actual fact it isn’t. So, if you run a five-minute benchmark on an underclocked system, the benchmark actually runs for five minutes and eighteen seconds (6% longer). If you boost your multiplier to compensate for the lower BCLK, this means that your computer draws 6% more frames or completes 6% more floating point calculations, resulting in a 6% higher benchmark score. If you underclocked your BCLK by 20%, you would see a 20% gain in the benchmarks, and so on. You can see how this would be a bit of an issue for a benchmarking site like HWBot.

Moving forward, HWBot simply says that it’s “impossible to verify the veracity of a system performance” under Windows 8, and thus benchmarks performed under Windows 8 will no longer be accepted. The blog post also says that all previous Windows 8-based records will be disqualified, though some comments from the moderator suggest that they’re still deciding if this is the best course of action. The moderator also says they don’t think that this flaw in the Windows 8 RTC is being actively exploited, but it’s obviously a case of better-safe-than-sorry.

For Microsoft’s part, this issue can probably be fixed with a patch, though it might be difficult given Windows 8’s cross-platform nature. It will be interesting to see how quickly Microsoft responds, because benchmarking tools really have no recourse without an accurate RTC. Having an entire operating system outlawed from one of the world’s biggest benchmarking sites is a big deal. For now, PC enthusiasts have yet another reason to stick with Windows 7.

Follow up post: Windows 8 RTC overclocking issues are blown way out of proportion

