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Posted at 5/7/2017 04:59:41
Only Author
9#
Update: I have received the heatsink from Firefly, and decided to run a relative performance test.
Methodology: I repeated the methodology above, thoroughly cleaning off the SOC with rubbing alcohol and lint-free cloth, before applying the same thermal paste. Note that the pressure on the SOC applied by both the stock cooler and the heatsink is less than on a typical PC, and so I applied some additional force in both instances to ensure that the thermal paste was distributed well. The ambient thermal environment is non-ideal (a closed cupboard), with almost zero airflow, and no precise temperature control; meteorological conditions including temperature and humidity almost certainly differed, as so there is likely some experimental error. Also, the system is operated headless, with modest background jobs, and the test involves running an intensive HandBrake software video transcoding job which utilizes almost the full capacity of each CPU core.
Idle temperature: I waited until temperatures had stabilized before starting the test, in order to ensure an accurate idle temperature. Previously, this was 50 C (CPU/zone 0) and 44 C (GPU/zone 1) with the stock cooler, operating at 408/816 MHz; In this instance it was 51/48 C with the heatsink, at the same frequencies. I do not account for the differences, which is likely within experimental error due to ambient conditions.
+0 min: Temperatures started to climb rapidly from starting temperatures of 51 C (zone 0) and 48C (zone 1). The CPUs were operating nominally at 1.99 GHz (A72) and 1.50 GHz (A53)
+1 min: The zone 0 temperature started to hit a threshold of 70 C, at which point the A72 processors started to slow, initially alternating between 1.99 and 1.60 GHz. Handbrake performance is impacted by about -6%. In the previous test it took about 3 minutes to reach this stage.
+4 min: Zone 0 now ~72 C range, with processor speed continuing to step down, looking fairly stable at 1.42 GHz. Zone 1 temperature continued to climb, eventually stabilizing at around 67 C. Performance impact is about -20%. In the previous test it took 15 minutes to reach this stage.
+6 min: Zone 1 now fluctuating between 73 and 74 C, A72 processors alternating between 1.42 GHz and occasionally dipping to 1.2 GHz. Zone 1 temperature remains stable at around 68 C. Performance hit consistently around -20%. This is about the same performance as was reached after 20 minutes in the previous test.
+10 min: No significant change, except temperature are now closest to 74/69, and the A72 processors are operating more consistently at 1.2 GHz. -24% performance hit. No major change after this.
Conclusion: The stock cooler used as a passive heat sink (unplug connector from board) offers no worse, maybe even better performance, than the purchasable heat sink. I would not recommend switching if you intend to run the RK3399 fanless; Simply unplug the connector from the fan to the board. A copper heatsink with a more complex vane structure might help, but I am aware of no available sinks that will work. Another approach might be a larger, more quiet fan providing flow across the board |
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