These benchmarking guys are not typical Windows uses. Regular users probably appreciate NTP updates.
This has nothing to do with NTP.
Windows 8 Benchmark Records No Longer Accepted
21–30 of 31 posts
Re: Windows 8 Benchmark Records No Longer Accepted
#22Earlier quoted context omitted.
Windows only reads clock at startup and writes it shutdown.
And so does my Fedora install (let's not blame Redmond unnecessarily). My Android phone is even worse - it drifts by about 5-10s a day. Not a nightmare but it's still a lot more than my (probably unrealistic) expectations of 21st century hardware.
Here Redmond is blamed for not providing any API to access the physical RTC chip and for switching old APIs to use CPU cycle counter even on RTC-equipped systems.
You can still run hwclock on your Fedora box and get genuine RTC readout if you need it.
Re: Windows 8 Benchmark Records No Longer Accepted
#23I'm a little confused. Does Windows 8 initially use the real time clock and the MHz as reference without checking if the MHz does change over time?
The Time Stamp Counter on modern CPUs runs at the same speed regardless of the CPU frequency or idle state, providing that the base clock isn't modified. Under normal use, that's absolutely fine - the OS can calibrate its internal clock against a wall clock timesource at boot time, and then use the TSC (which is very cheap to read, unlike the actual RTC) as a reliable time source. The problem here is (apparently) tha…
> So yeah, Windows 8 appears to use the CPU TSC without recalibrating when there's a change in TSC tick rate, but that's because the TSC tick rate isn't supposed to change.
Right - I'd say that the problem they're having is just a bug in the program they use to change the tick rate at runtime, that is, not making the kernel aware of the change. The article is written as if there is something fundamentally wrong with clock implementation on Win8.
Re: Windows 8 Benchmark Records No Longer Accepted
#24Earlier quoted context omitted.
My car also has a drifting clock without a dynamic CPU, losing two minutes every three months. It also doesn't have the ability to sync with NTP so it can't correct itself. Apparently clocks are hard.
Clocks are easy. Even accurate clocks are easy. However, accurate clocks are expensive which is where the problem is
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Re: Windows 8 Benchmark Records No Longer Accepted
#25Earlier quoted context omitted.
The Time Stamp Counter on modern CPUs runs at the same speed regardless of the CPU frequency or idle state, providing that the base clock isn't modified. Under normal use, that's absolutely fine - the OS can calibrate its internal clock against a wall clock timesource at boot time, and then use the TSC (which is very cheap to read, unlike the actual RTC) as a reliable time source. The problem here is (apparently) tha…
> So yeah, Windows 8 appears to use the CPU TSC without recalibrating when there's a change in TSC tick rate, but that's because the TSC tick rate isn't supposed to change. Right - I'd say that the problem they're having is just a bug in the program they use to change the tick rate at runtime, that is, not making the kernel aware of the change. The article is written as if there is something fundamentally wrong with…
Because the TSC speed is never supposed to change at runtime, I would guess there is no API to notify Windows that you changed it.
Re: Windows 8 Benchmark Records No Longer Accepted
#26Earlier quoted context omitted.
And so does my Fedora install (let's not blame Redmond unnecessarily). My Android phone is even worse - it drifts by about 5-10s a day. Not a nightmare but it's still a lot more than my (probably unrealistic) expectations of 21st century hardware.
Here Redmond is blamed for not providing any API to access the physical RTC chip and for switching old APIs to use CPU cycle counter even on RTC-equipped systems. You can still run hwclock on your Fedora box and get genuine RTC readout if you need it.
hwclock will only give you 1second resolution, because the RTC chip can't do better. But querying the RTC directly is dog slow by todays standards, it's accessed via 8-bit port IO where one access eats up thousands of cpu cycles on a modern chip.
The really old way of timekeeping was to basically advance the system time by a constant amount, in an interrupt routine which might have been triggered by the ancient timer chip, and interpolation done between those ticks using the cpu TSCs.
And actually hwclock accesses /dev/rtc* which is just an arbitrary character devices (which the kernel indeed can use to initialize its notion of time on boot up), it's never accessed with the standard syscalls gettimeofday() or clock_gettime().
So while I really like MS bashing from time to time, in this case it's probably not too negligent of them, there might even be a standard way of informing the OS kernel about a change in TSC speed?
Re: Windows 8 Benchmark Records No Longer Accepted
#27This has been a significant issue on the windows 8 machines I've handled. It's mitigated somewhat by creating your own scheduled task to more frequently do ntp updates. I like this guide: http://www.pretentiousname.com/timesync/
You modify the BCLK regularly whilst booted into Windows on the different Win 8 machines you handle? Even when overclocking you'd normally not mess with the BCLK unless you are really wanting to push your overclock.
Windows 8 keeps terrible time on laptops or anything else which is trying to power save by varying the clock. I'm not overclocking shit. The OS just doesn't time sync frequently enough. This is why I posted a link about increasing the frequency of time syncs.
This has not been a problem with Windows 7, or XP on the same equipment.
Re: Windows 8 Benchmark Records No Longer Accepted
#28So this only affects you if you change BCLK at runtime. Which is something that basically never happens unless you do it yourself explicitly. Dynamic CPU speed only modifies multiplier which does not cause this issue. This is a non-issue for 99% of people, it's only an issue if you are measuring your manhood on an internet website.
It's also an issue for anyone who's overclocked their gaming rig, as the computer won't keep accurate time anymore. See this video for a demonstration of that:
http://www.youtube.com/watch?v=brkDKgvXKko&feature=player_em...
Re: Windows 8 Benchmark Records No Longer Accepted
#29Earlier quoted context omitted.
You modify the BCLK regularly whilst booted into Windows on the different Win 8 machines you handle? Even when overclocking you'd normally not mess with the BCLK unless you are really wanting to push your overclock.
Windows 8 keeps terrible time on laptops or anything else which is trying to power save by varying the clock. I'm not overclocking shit. The OS just doesn't time sync frequently enough. This is why I posted a link about increasing the frequency of time syncs. This has not been a problem with Windows 7, or XP on the same equipment.
That is not how the power saving works. It does not vary the BCLK rather it alters the multiplier. If it varied the BCLK by such large amounts to achieve typical low power frequency levels then you'd likely run into some catastrophic stability problems as the BCLK is also used by the integrated memory controller and QPI.
Re: Windows 8 Benchmark Records No Longer Accepted
#30So this only affects you if you change BCLK at runtime. Which is something that basically never happens unless you do it yourself explicitly. Dynamic CPU speed only modifies multiplier which does not cause this issue. This is a non-issue for 99% of people, it's only an issue if you are measuring your manhood on an internet website.
It's also an issue for anyone who's overclocked their gaming rig, as the computer won't keep accurate time anymore. See this video for a demonstration of that: http://www.youtube.com/watch?v=brkDKgvXKko&feature=player_em...
Why are you overclocking at run-time vs the simpler BIOS time overclock?
Sure while you are testing stability making run-time changes is nice, but once you know what your system can handle it makes sense to just set that permanently.
Also hopefully a fix will come out soon, since it is already well known that the ratio is allowed to change.