Stuttering - FPS suddenly low (1 Viewer)

[HTPCSourcer]

Hi,

I recently set up a Baytrail 3735-based mini-PC as MP-Client. All was good until yesterday, when I suddenly realized that the picture on the new HTPC2 (see sys specs) was choppy, particularly on Sky 1080i channels:



Despite the supposed 50 Hz, all I get is 30fps. No surprise that the picture is crappy. Even a standard 720p produces just 40fps. The CPU load when running TV in windowed MP is ca. 20% and hardware acceleration is obviously operating.

I can't tell for sure when this occurred the first time. Unfortunately I have been doing some extensive work on the system the last two days, e.g. optimizing TV settings, running .Net updates, etc.. Windows Update history shows .Net 4.5.2 and the respective language package as newly installed but for some reason it's not listed under software...

Given that two other clients have no such problems, I think that the server side can be excluded as the source of the problem. Unfortunately I also cleaned up the log directory and therefore can't really say much. I will collect new logs, but wanted to ask in the meantime if anybody had an idea in which direction to search.

 

[HTPCSourcer]

Here are debug logs taken for a Sky 1080i channel. 30fps with almost one of 2 frames dropped.

The same frame rate is showing when playing an otherwise perfect 1080i recording. I also had he impression that shutting the PC off and then restarting would give me 50 fps for a some minutes or so before it drops back to 30. However, as I have no keyboard connected, I can't easily activate Shift-1.

 

[Owlsroost]

I also had he impression that shutting the PC off and then restarting would give me 50 fps for a some minutes or so before it drops back to 30

Could it be getting too hot (and throttling down the GPU clock in response) ? - that might explain why it runs OK for a few minutes after a restart.

If GPU-Z supports the Z3735, you could use that to check on the GPU performance while playing TV in MP.

 

[HTPCSourcer]

Thank you Owlsroost,

This seems to be the right direction.

After reading your posting I powered the Justop back on and started to play a 1080i recording and monitored the CPU speed (CPU-Z). Frequency was oscillating between 500 MHz and 1000 MHz, occasionally going up to 1350 MHz for a short time. Multipliers were changing as well from 6 to 14 (I believe). The movie was playing nicely for about 5 min at 50fps with the red curve being nicely flat. Then, after about 5 min, things changed and the frame rate went down to 40 fps. After a few more minues CPU-Z showed a constant frequency of 500 MHz with a then stable multiplier of 6.

The bottom of the Justop was really hot then. It looks as if the thermal design of the device is not well thought. As it stand, the Justop is not usable as a HTPC client.

And now?

 

[Owlsroost]

Better passive heatsinking ?
A quiet fan to circulate air within the box?

You have to accept that these PCs are basically tablets-in-a-box, and can have heat-versus-performance issues like tablets and phones do.

 

[HTPCSourcer]

You have to accept that these PCs are basically tablets-in-a-box, and can have heat-versus-performance issues like tablets and phones do.

Yeah, I am nonetheless frustrated about it.

This is what it looks inside.



I also removed the four screws that hold the board, but it still sticks to the case. I assume that the case itself is used as a heatsink, which would explain why the bottom is getting so hot. This suggests that CPU/GPU are at the other side of the board, in which case a fan would not be very efficient. Maybe adding an 8mm aluminum plate at the bottom of the case. I would need o take the board off - at the risk of braking it.

 

[Owlsroost]

I assume that the case itself is used as a heatsink, which would explain why the bottom is getting so hot.

I agree. You could try glueing (with heatsink glue) a finned heatsink to the outside bottom of the box (after removing the paint from around the area where the chip is - i.e. the hottest part of the bottom). Then stand the box on tall feet or stand it vertically to get better airflow over the heatsink.

Just to check if it's worth trying a heatsink on the outside, try running it with a fan (or hairdryer on 'cold') cooling the base of the box. If that keeps it running properly then you might be OK, if not then there is probably not much you can do.

 

[RonD]

if you look in WindowsEventViewer > WindowsLogs > System, you probably have a bunch of "Microsoft-Windows-Kernel-Processor-Power" events. Like they said in the movie Jaws, "Your gonna need a bigger heatsink/fan". The following is text save of 1 of the error events from my Win8.1 laptop.

Level Date and Time Source Event ID Task Category
Warning 1/10/2015 1:05:21 PM Microsoft-Windows-Kernel-Processor-Power 37 (7) The speed of processor 0 in group 0 is being limited by system firmware. The processor has been in this reduced performance state for 71 seconds since the last report.

 

[HTPCSourcer]

The solution appears quite simple:

I took the heatsink of an old graphics card that was still lying around and just placed it on the bottom (case upside down). No thermal paste or anything applied.



Then I put a 720p TV station on, which presents little load for the GPU. The heatsink immediately started to get warm. After 45 min the fps was still at 50.
After that I switched to a 1080i station. The fps quickly dropped a little bit, but pressing the heatsink to the surface of the case brought it back to 50 fps.

This lets me believe that a correct mounting of the heatsínk by using heatsink glue will solve the issue without having to completely unmounts the device. Screwing it to the case would obviously be better, but drilling a holes into it with the electronics still in it, is probably not a good idea. I am also thinking of adding a small heatsink on the big metal cover on the board (see picture of the open case above) and also drill a series of venting holes into the top of the case cover. There would even be enough space left inside the case to add a small fan.

In fact the case design is close to being stupid:

• There are venting openings at the bottom of the case, but it comes without spacers.
• There are no venting openings on the top of the case.
• The removable top part of the case, which is painted black, has practically no thermal connection with the bottom. While the latter gets hot, the top stays cold.

 

[HTPCSourcer]

I have opened a new dedicated Justop thread here: https://forum.team-mediaportal.com/threads/justop-g-pc-quad-core-windows-8-1-mini-pc.131388/