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I'm trying to understand the firmware on the Raspberry Pi.

My understanding was that firmware related only to persistent software not influenced by anything which is on any particular SD card, but it seems that's not the case on the pi and that firmware is also being used to describe low level boot states that are loaded from the SD card.

I would like to know are there any user upgradable firmware settings that do persist without reference to any particular SD cards contents? If so, which ones (in general terms)?

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As far as I am aware there is no user upgradeable memory or firmware within the Pi. There are a few bits of One-Time Programmable (OTP) memory once used to record usage which invalidated the warranty.

All state is held within the SD card.

  • Hi and thanks for the answer, I really was hoping for a different one but think I suspected as much. I can't make sense of a problem that I was having - the wireless network interface seemed not to exist on a Pi0W until I updated the SD card on another Pi and inserted it back into the 0W, when all was fine. I then re-imaged the card from the same .img file and expected the same problem to recur - it didnt. It seems the original problem (no wifi adaptor) and solution has occurred a few times and the Pi is working fine but why the problem didn't come back on the 2nd pass is an itch for me. More – nick soph Apr 13 '17 at 21:06
  • The Pi3 also uses OTP to control boot mode. – Milliways Apr 14 '17 at 1:09
  • @Milliways I didn't know that. What does it do? Control net boot or similar? – joan Apr 14 '17 at 7:39
  • @joan I haven't actually tried this myself (having no desire to netboot or boot from USB) but this came out of reading raspberrypi.org/blog/pi-3-booting-part-i-usb-mass-storage-boot and some of the following links which include "The flow of boot begins with reading the OTP to decide on the valid boot modes enabled." – Milliways Apr 14 '17 at 7:52
  • @Milliways Like you I have no desire to net or USB boot so am not familiar with the procedure. I suppose some reading is in order. – joan Apr 14 '17 at 8:04

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