High temp reading with Xtemp - 95

[AndyC]

Hi Guys,

I have my Parallella 16 Z7020 setup here. New one with large heatsink installed as per instructions on site.

Just running vncserver and Xtemp so basically ideleing but the reported temp is 95.

This seems a little high! Ambient here is about 25 at the moment.

Any ideas?

Andy

[FHuettig]

Hi Andy,

95 is much too hot, you want to keep the xtemp readings below 70 or as close as possible. By any chance are you running your board inside a case or other enclosed space? The heat sink, _any_ air-cooled heat sink, is only good at transferring heat to the surrrounding air and then the hot air must be replaced with cooler air. This replacement can happen by convection or be forced by a fan, but if there is nowhere for the hot air to go it will just continue to heat up. The large heatsinks are only "fanless" if operated in the open, any enclosure will require a fan. HTH

[AndyC]

Hi, Thanks for the reply.

It is just sitting on the desk.

I turned it off and let it cool down till the heatsink was cool to the touch.

Then I started it up and used the script on the forum to display temp using watch. Cpu load is around 10% using top.

Started at 65 and is gradually working its way up, currently at 77C after maybe 5 minutes. The heatsink is nowhere near that hot though, I can hold my fingers on it with no problem.

[AndyC]

Ok, it stabilised at 77.

So I loaded up the two cores and left it running.

It seems pretty stable at 79C, I must have misread 95 on the temp display, it was a bit garbled!

I'm going to shut it down for an hour or so and try it again....

[AndyC]

Ok, I really don't understand this temp readings.

I have run tests with HDMI and Headless

HDMI idle : 77C
HDMI 200% CPU Load 80C

Headless idle: 76C
Headless 200% CPU load: 79C


So basically the difference I see between idle and 200%CPU is only 3C

Surely this must be a bad temp sensor?

[FHuettig]

[AndyC]

Ok Thanks.

So what would you say my issue may be?

I fixed the thermal tape as per the instructions, the heatsink does get pretty hot after a while.

Do you think it is worth removing the heatsink and reapplying it with new tape or does the big heatsink require a fan as well?

Thanks for any help

Andy

[AndyC]

ok, I got a 6cm 12V pc fan and laid it on top of the heatsink drawing air up.

Running this at 5V keeps the heatsink very cool, and at 200% cpu load the temp is 57C

So this maybe looks like my solution.

[deviantlamb]

do you have access to a temp probe of some kind to validate the temps on? mainly the base of the heatsink.
Secondly are you sure your chip (both of them!) are in fact well contacted to the heatsink?

[AndyC]

Nope, using the temp sensor on the zynq.

My bet is the chips are well contacted to the heatsink as the heatsink gets extremely hot when the fan is not used, but of course I have no proof.