I'm running an electronic photoframe based on a Pi Zero W running Stretch lite 2018-11-13. The photoframe boots the auto login and starts a script that run "fbi" in loop to display images found in a USB key, at a pace of one per ten seconds.
The setup ran for almost two years with a Pi Zero and then I changed it to a Pi Zero W to be able to update the image set via WiFi. So far so good. It ran fine for almost 2-3 months.
Some day I remarked that the picture froze and did not change any more. It can occur after many minutes to few hours of perfect running. Also, it can freeze on any image. It is not always the same one.
When the image is frozen, the display is "perfect" in the sense that it doesn't flicker neither show other artifacts. It just stays on the same image forever. When this occurs, it is not possible to connect to the Pi via SSH. So I guess the processor is hung.
Question: why, if the CPU is stalled, is the image still correctly displayed? Any clue on how to fix this? I must admit that I already got my replacing Pi... I won't waste many hours on this problem but I would like to know why this behaviour occurs...? Any suggestions?
Thanks in advance for sharing your knowledge!