Temperature of set-top devices

So I’m experimenting with Raspberry Pi cases at the moment. The stock case comes with a fan which isn’t great, but typically it keeps the CPU temperature below throttle temperature. (80C)

The “active cooler”, which is a bigger fan that attaches directly to the CPU with a heat sink (and replaces the case fan) is better in that it’s quieter and keeps the temperature a little lower.

Both or these options do incur a little background fan noise when the machine is heavily loaded, and the do blow out a little hot air.

My latest test is an aluminium case with no fan. For the most part this seems to keep the CPU cooler than the fan based options. However as the case itself is the heat-sink, it does get quite warm (albeit by design).

Anyone have any thoughts / feelings re; how hot is too hot for the case on a set-top style box? (2.5" x 3.5" x 1")

Typically what would be your preference in a desktop Computer?

  • Prefer a cooler case, can live with a little noise
  • Prefer silence and can live with warm case
0 voters

I’ve now switched and am running my entire development desktop from a Pi with the standard Ubuntu Gnome Desktop (23.10), 2x4k screens @ 27". Whereas I’ve been waiting for NVMe / M.2 for speed, I’m finding a plugin-in USB SSD @ 350Mb/sec is plenty for a desktop (old hard drives used to do ~ 100) and the ability to just unplug my storage from one machine and plug it into another, is a whole new world :slight_smile:

Little bit more in terms of temperature profile, typically the CPU is idling at around 53C and goes up into the low 60’sC when I start to do things. If I hit it hard it might go up into the low 70’sC but doesn’t start there too long.

At idle it’s eating 4-5W, when I hit it hard, anything up to 11W, but typically it will fluctuate between 5W and 9W. This is stupidly low, I have some (granted maybe older) 4-core AMD machines here based on desktop boards that can hit up to 150W under load with the same sort of memory and storage.

How is Gnome in 8Gb?

So, I’m used to KDE running in 32Gb (!) so Gnome in 8GB is a little different. That said, there are some tricks available to effectively make more than 8G available on a Pi. I’ve found this quite interesting, although I’m sure it results in additional CPU which is probably increasing the heat a little;

So I’m using ZRAM as my swap-file, seems to do quite a good job, although even with two different browser running, VS code, a bunch of monitors and terminals, I still seem to have 2-3G of available RAM, so at the moment my ZRAM isn’t working too hard.

# zramctl 
/dev/zram2 zstd           31G  4.4M 100.7K  236K       4 /zram
/dev/zram1 zstd           31G    4K    59B   20K       4 [SWAP]
/dev/zram0 lzo-rle       3.9G 38.7M  38.7M 38.7M       4 [SWAP]

(so looking at the system monitor shot above, ZRAM swap presents as swap space)
There are some really nasty web adverts about which seem to cause some stuttering (but then I was also seeing that on my old box) , but other than this there seems to be quite a lot of juice in the CPU.

Many thanks for your detailed description of your experience of the Pi - keep it coming.
I am becoming increasingly persuaded to move in this direction when funds allow - perhaps in the winter.

Mmm, rather embarrassingly the fan-less case is running ~ 10C cooler today, and indeed the temperature is much steadier. There is a thermal pad that you stick to the CPU to interface between the case and the CPU. What occurred to me overnight was that the thermal pad was likely a double-sided sticky (!) , so this morning I peeled off the membrane on the other side of the pad :blush:

Temperature range with both sides of the thermal pad doing their job ...

(green in temp, blue is cpu)

We’ve all been there!

Mmm, so not gone over 64C all day today and mostly seems to hang around 52C.
(general / normal usage, 25 browser tabs, 10 terminal Windows and other random)

I reckon this room is ~ 18C, so under normal usage, so it looks like the case would top-out and the machine would throttle (at peak normal usage) when room temp hits 34C, which from experience is so hot working in this room is impossible.

Ok, so despite online commentary to the contrary, if you load up an RPi5 in a FLIRC case, it will eventually saturate and go into thermal throttle. At this point it automatically tweaks the CPU frequency to avoid the CPU temp going over 85C.

As soon as you remove the load, the temperature drop-off is pretty dramatic, so this is very much an artificial test. For “desktop” usage the case is fine, but if you want to load it up with intensive calculations over an extended period, and don’t want it to slow down at all, then you need a fan.

The stock plastic case however with the active cooler, doesn’t go above 75C under the same load. Reason; at 75C the fan switches up to max speed, which is enough to actually bring the temp down, even under max load. You can however hear it doing so and it’s not an ongoing noise I would want on my desk (!)

In terms of the FLIRC throttle, the clock speed will vary depending on load, but the normal (max) clock is 2.4G. During throttling, I didn’t see it drop below 2.1G, so it’s not a massive performance drop.