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- Overall, regarding the effect on FPS, the differences I saw were so small that they can only be put down to margin of error, but this is the conclusion I've come to:
- Timers
- High Precision Event Timer is enabled or disabled in the BIOS
- bcdedit is configured via an elevated command prompt
- TSC+LAPIC - Seems to cause no latency or stutter, input and output are smooth (normally the default)
- High Precision Event Timer: Disabled
- bcdedit /deletevalue useplatformclock
- LAPIC - Seems to cause stutter but no latency
- High Precision Event Timer: Disabled
- bcdedit /set useplatformclock true
- TSC+HPET - Seems to cause latency and stutter
- High Precision Event Timer: Enabled
- bcdedit /deletevalue useplatformclock
- HPET - Seems to cause latency but no stutter, input and output are very, very smooth
- High Precision Event Timer: Enabled
- bcdedit /set useplatformclock true
- The following I've probably just made up:
- I think the TSC timers are relative to each processor, the LAPIC timer is relative to the system bus and HPET is external. TSC timers can't be used alone because they don't stay in sync hence why HPET and LAPIC are either used instead of TSC, or are used as well so that the TSC timer's very low latency can be taken advantage of without the issue of them going out of sync. I think that TSC and LAPIC derive their times from the same clock/crystal so they fit quite nice together but HPET doesn't and this is probably part of the reason why using HPET causes problems with latency and stutter since it's not going to be in sync with everything. The purpose of the really high frequency might even be just an attempt to mitigate the sync and latency issues with HPET, rather than any sort of performance improvement, but the high frequency actually causes issues of it own, especially when HPET is used on it's own, which is probably why it's not used by default.
- Times stamp counter synchronization policy
- Setting this to Enhanced either had no effect or caused stutter, from what I now understand Windows already picks the best setting for this so it should be left alone.
- To force setting to enhanced:
- bcdedit /set tscsyncpolicy Enhanced
- To remove the forced setting:
- bcdedit /deletevalue tscsyncpolicy
- Dynamic timer tick
- Neither had any noticeable effect but it's documented to have caused issues before, it also offers nothing of any real benefit and isn't used or needed in Windows 7 or previous so I've chosen to disable it.
- To disable:
- bcdedit /set disabledynamictick yes
- To enable:
- bcdedit /deletevalue disabledynamictick
- So in the end it would seem (at least in my case) that messing with these settings offers nothing of benefit other than the chance to correct the often overlooked and ignorantly misconfigured HPET BIOS setting. ^.^
- --------------------------
- What i did:
- TSC+LAPIC - Seems to cause no latency or stutter, input and output are smooth (normally the default)
- High Precision Event Timer: Disabled
- bcdedit /deletevalue useplatformclock
- Dynamic timer tick
- Neither had any noticeable effect but it's documented to have caused issues before, it also offers nothing of any real benefit and isn't used or needed in Windows 7 or previous so I've chosen to disable it.
- To disable:
- bcdedit /set disabledynamictick yes
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