I'm a bit confused with "Luckfox Pico Mini B" board specification. According to information from LuckFox Wiki this board has 64 Mb DDR2 RAM. But as I can see this board adopted RV1103G1 chip which has 512 Mb RAM according to the datasheet:

https://i.ibb.co/jPxSxfvs/image.png

Could you explain it ...

I've got LuckFox Lyra Plus SBC. My board has NAND flash with stock firmware, but I want to boot Ubuntu from SD card. I flashed Ubuntu image into my SD-card and inserted it into my board. But it still boot into NAND Buildroot image. How to choose which media will be boot (NAND or SD card)?

I've done the investigation myself via putting RV1103 LuckFox development board into thermal chamber for 45 minutes at -30 degrees and it stopped work. I have no idea what part the problem is: CPU, DDR memory, SD-card, but it obviously doesn't work at -30 in total.

Sad to hear this. I really need a processor with a realtime core.

That is not a "range", this is "absolute maximum" value. My goal is to know the minimum working temperature.

I found only recommended temperature range for RV1106 processor (0-80 centigrade) in a datasheet. What is the maximum temperature range? Are there chips with industrial temperature range (-40...+85 centigrade)?
What is the temperature range for RV1103 processor? I didn't find any information in the ...

I didn't find any information what MCU core is (even in a datasheet). Whare can I get this information? Also I wanna know how to develop applications for this core and examples for interprocessor exchange. Where can I get it?