1. Disable EIST (Intel Speed Step) and all c-states in the BIOS, e.g. C1, C3, C6, C7, etc. The theory is you don't want the CPU to down clock or go into wait states, this increases latency I believe.
2. Set Windows Power Profile to "High Performance".
3. Disable Pagefile (if you have enough RAM for your workload). RAM is pretty cheap, having a pagefile I find is laggy even if you have more than enough ram for what you're doing.
4. Install all the latest drivers for your devices, unless you have an issue that requires an older driver.
This includes intel chipset, gpu drivers, network drivers, etc.
5. Run an elevated CMD.exe and type "bcdedit /set disabledynamictick yes" - With dynamic tick enabled, the system will typically have 1,000 microseconds of latency when the cpu is not under load. It makes it difficult to measure system latency, since to undo the effect of dynamic ticks you have to increase load, but increasing load on the cpu typically raises latency too. It's a power saving feature added to Windows 8, and the reason DPC Latency Checker explains it does not work on that OS I believe.
6. I have a couple of reg files that tweak things for lower latency. First one stops Windows from updating a time stamp in the registry that's really not useful, but causes the C: drive to be accessed every couple of seconds:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Reliability]
"TimeStampInterval"=dword:00000000
6. b. Second one disables auto-play for optical media, this also causes the C: drive to be accessed a lot for some reason, and this is supposed to be the only way to disable it that eliminates the accesses:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\cdrom]
"AutoRun"=dword:00000000
7. Disable useless audio devices, under control panel -> sound. Just right click any audio device you don't use and microphones in the microphone area, and select disable.
8. For knowledgeable and/or patient users, find a guide for disabling services you don't need in services.msc. There are many, I'm aware of one by a guy calling himself "black viper" that you may want to start with however. His guide tells you what a service does, and under what situations you need it, so you can decide to disable it if you want to possibly reduce some latency.
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