High Precision Event Timer

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10-19-2010, 03:11 AM
Carfax

High Precision Event Timer

Can anyone explain to me what HPET does exactly?

A guy on another forum claimed that by disabling it, his DPC latency plummeted and his gaming performance improved; most notably the microstuttering.

So I tried it myself, and the difference to my astonishment, was very noticeable. First off, my DPC latency dropped big time. Not that it was high to begin with, but now it hovers below 10 for the most part.

Second, I noticed that general windows performance felt snappier. I know I'm not imagining things, because like many, I scrutinize my system so I'm sensitive to even minute changes in performance.

And last but not least, gaming performance is definitely smoother. Anyone with SLi will tell you that occassionally when playing a game, you experience a bit of lag or stuttering for no apparent reason whatsoever. Most people attribute these minor discrepancies to SLi, but what if it's something else?

Because I can tell you, that my overall gaming experience has improved since turning HPET off :yepp:
10-19-2010, 05:41 AM
CrazyNutz

HPET is High Precision Event Timer. It's exactly that..
It can be used by software or the os for very accurate timing, however when it's "ON/Enabled" then windows will use it as the main clock source instead of the other options like the cpu TSC (time stamp counter).

The HPET can provide more precise timing, however the OS has to reference it via a memory address, or I think the HPET can raise a interrupt,
so therefore it's slower.

The TSC may be less precise, however it's a register in the CPU so this is the fastest possible way to access a clock source.
10-19-2010, 05:58 AM
zalbard

Disabling it is a great tip. I couldn't figure out why my DPC latency was so high before. It shouldn't cause high latency, though... :\ Needs fixing by EVGA.
10-19-2010, 06:10 AM
chuchnit

Carfax can you run some benches to see how much difference it makes? Say Vantage and 03?
10-19-2010, 06:29 AM
ezgonzo

very interesting, i would also be interested in seeing if it makes any difference to benchmarks.
10-19-2010, 08:30 AM
Carfax

Quote:

Originally Posted by CrazyNutz

HPET is High Precision Event Timer. It's exactly that..
It can be used by software or the os for very accurate timing, however when it's "ON/Enabled" then windows will use it as the main clock source instead of the other options like the cpu TSC (time stamp counter).

The HPET can provide more precise timing, however the OS has to reference it via a memory address, or I think the HPET can raise a interrupt,
so therefore it's slower.

The TSC may be less precise, however it's a register in the CPU so this is the fastest possible way to access a clock source.

Great explanation dude, thanks :up: If the TSC runs from the CPU register, then that could definitely explain the performance increase I'm seeing..

BTW, I opened up a similar thread on Nvidia forums and some of the replies are interesting.

Quote:

Originally Posted by zalbard

Disabling it is a great tip. I couldn't figure out why my DPC latency was so high before. It shouldn't cause high latency, though... :\ Needs fixing by EVGA.

Do you have an Nvidia card? It's possible that Nvidia drivers may have issues with HPET.

Quote:

Originally Posted by chuchnit

Carfax can you run some benches to see how much difference it makes? Say Vantage and 03?

I'm waiting for my monitor to return from repair before I start running benchmarks. It's supposed to be here tomorrow, so if I have time, I'll run them then..

I can run some Everest benchmarks to see if there are any differences in bandwidth and latency in the mean time however..
10-19-2010, 08:37 AM
chuchnit

Quote:

Originally Posted by Carfax

I'm waiting for my monitor to return from repair before I start running benchmarks. It's supposed to be here tomorrow, so if I have time, I'll run them then..

Thanks :up: I'm waiting on my CPU to get here or I would test myself.
10-19-2010, 08:47 AM
Kain665

I'll test tonight. This actually makes sense, but I need to see how high my DPC latency is in the first place.
10-19-2010, 08:50 AM
Carfax

Quote:

Originally Posted by Kain665

I'll test tonight. This actually makes sense, but I need to see how high my DPC latency is in the first place.

Use this tool to see what it is.
10-19-2010, 08:57 AM
zalbard

Quote:

Originally Posted by carfax

do you have an nvidia card? It's possible that nvidia drivers may have issues with hpet.

5870.