Allwinner A20 cooling or power problem?

[PLyttle]

Hi all

Reading the various remarks on temperature problems with Allwinner A20 systems, I immediately suspected overheating when my boards started misbehaving . The symptoms were spontaneous reboots, with sometimes disk corruption, while there was no indication of the cause of the problem anywhere.

Somehow, increasing the cooling did not help, so I installed a kernel patch I found here: https://groups.google.com/forum/#!topic ... zoxTcepPVo
which gives access to the A20 temperature sensor which is internally wired to the resistive touch panel interface. You need to be a bit creative, applying the patch, because it does not really "fit". The first time I did it by hand, and then made a better patch.

Imagine my surprise when I noticed the chip never reached 40 degrees centigrade, with a minimal heatsink in use (22 K/W). Temperature clearly was not the problem.

I realized that the problems started at the same on both my Allwinner boards (a Cubietruck and a Phoenix A20), when I started using fast SD cards (Samsung EVO 16 GB). So I started to suspect the power supply,

Reading the current amps and voltages in $this->bbcode_second_pass_code('', '/sys/devices/platform/sunxi-i2c.0/i2c-0/0-0034/axp20-supplyer.28/power_supply/ac/current_now
and
/sys/devices/platform/sunxi-i2c.0/i2c-0/0-0034/axp20-supplyer.28/power_supply/ac/voltage_now ') (no need to whip out your multimeter) gives something like 500 mA at 5.1 volts. which is also no reason for alarm, but this doesn't account for surges.
Changing the 2 Amp "wallwart" for a 5 Amp "brick" made all the problems go away. It is nicely chugging away compiling a kernel with 2 cores at 1008 Mhz at a balmy 39.7 degrees centigrade, and no more sudden reboots.
(compiling a kernel this way takes just under 2 hours)

I assume the above is also true for Cubieboard-2 which gets a bad rep for overheating, Off course when you put it in a box, you can expect higher temperatures and you need to provide sufficient airflow. But in case of problems I would look at the power supply first. and the patch is a big help in locating the problem.

LP

[tomcheng76]

my cubietruck is fine, it is powered by ipad charger because it has 2.1A, did you check your power supply ?

[PLyttle]

My cubietruck was fine too, until I started using fast (read: power hungry) SD-cards combined with heavy duty dual core compiling. It is not so much the amps, but the reaction to power surges, or how fast the power supply is, that matters. In other words, how much does the voltage drop if the current all of a sudden jumps up.

I believe I said that I swapped the PS for a 5 amp brick? (used to be a 2 amp USB-hub power supply.)

My cubietruck is doing fine again (and I can read the core temperature now

My problem is solved already, maybe it can help someone else...

LP

[tomcheng76]

yeah, both overheat and power supply problem may happens...

thats why cubietruck comes with a "heatsink" in the "valued" pack, although the heatsink may not be enough, but mine is fine.

Also power supply is important, at least 2A for normal use, if you attach harddisk, 3A is required, i use a external 3.5" usb harddisk that comes with power supply, so the cubietruck is pretty stable.

We have trouble when finding a good power supply, i know, if we comment "this sdcard may not work, that power supply may not work", then this product may not be a good product.

But, bear in mind those ARM board are developer board, and they need to cut cost in order to keep the price cheapest, so those "side effect" are acceptable.

Although i really hope they bundle a workable power supply in their "valued" pack instead of "premium" pack

[tomcheng76]

btw, this is my reading
$this->bbcode_second_pass_code('', 'cat /sys/devices/platform/sunxi-i2c.0/i2c-0/0-0034/axp20-supplyer.28/power_supply/ac/current_now
256000
cat /sys/devices/platform/sunxi-i2c.0/i2c-0/0-0034/axp20-supplyer.28/power_supply/ac/voltage_now
4967000')

[PLyttle]

For normal use the cubietruck heatsink is good enough. With it the A20 runs about 20 degrees above ambient clocking 1 Ghz. (11 above ambient, idling at 360 Mhz.)
There are many serviceable power supplies, but you generally get what you pay for. Check ebay: http://www.ebay.com/itm/New-AC110V-220V ... 38ca48722V . I now use the 25 watt version. 12 dollar US plus free shipping (some assembly required.)

LP