Booting, cooling and other "Novice's" questions

AlexNT

Hello, guys!
I'm really new to Orange Pi Plus 2 (but some years ago I played with Raspberry model B, then I've bought an Orange Pi Plus 2, which seems interesting, but I had no free time to play with it), so I want to ask you a couple of questions:
1) I know, that orange Pi Plus 2 has an overheating problem, which can cause damage to chip and to board. So, I decided to place a cooler, but the problem is that it doesn't cover all the chips: only CPU, and a half  every DRAM chip. So, is it OK? How should I pose the heatsink? What should it cover?
And should I cool the EMMC and SATA chips?
2) Is there any pre-installed OS in the onboard EMMC storage of Orange Pi Plus 2? What should show LED'S? (My board turns red led on, then blinks with green, turns of the green and turns on the red). Monitor displays Allwinner LOGO.
3) When the board in the state, so monitor shows allwinner logo, what does it mean? Does it have configuration setup (like BIOS)?
4) Is there any CPU overheat protection, while even the OS hadn't booted yet? Isn't it dangerous to power it on for ~5 minutes without the heatsink/cooler?
5) What is the logic level of Debug UART? 5V or 3.3V?
6) What the USB-OTG port can be used for? It means, that I could plug a USB-flash disk (through the OTG-adapter) to use the OPI as HOST and if i plug it to my PC, will the Orange Pi Plus 2 work as a DEVICE? Or what does it mean "USB OTG Port" on Orange Pi Plus 2?

Yes, I know, that I had to ask these questions earlier, when I acquired my Pi and to search the forum for answers. But sorry, I couldn't find the full answers to every question (maybe, because I didn't have the time - I forgot about that board for more than a month).
And yeah, thanks to everybody, who'll answer me!

shooreg

Well, here goes:

1) The overheating is mostly a problem of SoC, the other chips - DRAM, eMMC, USB-SATA bridge are not getting that hot.
2) Alwinner logo is usually displayed at the start of pre-installed to eMMC Android. But if you plug in an SD-card with correct linux image, it should start first.
3) If it doesn't go any further from the logo - looks like it is stuck at a bootloader. Might be a corrupt OS installed to eMMC. However, debug uart should be accessible even earlier than logo is shown.
4) With linux image, there is a cpugovernor, which shutdowns CPU kernels one by one when temp gets critical. But it is a far-from-perfect protection. Use a heatsink and an OS image that has correct voltage and clock speed configured in boot script.
5) Debug uart has a 3.3V TTL voltage
6) The OTG port is used mainly in Android like with Android phones, and as far as I know, for flashing image to eMMC directly from PC.

AlexNT

shooreg replied at 2017-1-20 22:28
Well, here goes:

1) The overheating is mostly a problem of SoC, the other chips - DRAM, eMMC, USB-S ...

Well, big thanks!
And what type of heatsink will work nice? Does the raspberry-like (small aluminium) heatsinks suit?
I found a chipset heatsink, 3x3 cm, which covers both CPU and DRAM chips. Won't the heat from CPU damage the DRAM chips, if they're covered by one heatsink?
Again, thanks for your answer!

shooreg

I have been using a 15x15mm heatsink from RasPi that covers just SoC (on OPI One) and a heatsink from x86motherboard south bridge (45x45mm) on OPI Plus. In second case it partially covers DRAM, but there were no issues in my case.
Just FYI, I'm using OPIs mostly as headless devices, and when NOT using a hdmi monitor SoC is much cooler - I guess GPU is producing fairly a lot of heat, at least with linux kernel/modules.

AlexNT

shooreg replied at 2017-1-23 19:28
I have been using a 15x15mm heatsink from RasPi that covers just SoC (on OPI One) and a heatsink fro ...

Thanks! I've bought some heatsinks, will try...