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By intern
#82781 I used esptool to dump some firmware: --port /dev/tty.usbserial-A908574Z --baud 115200 read_flash 0x00000 0x400000 backup.img

When I look at the header:

E9 01 00 40....

This tells me QIO, 40MHz, 4MB flash

When I look over the firmware dump, there are multiple copies of the program repeating 3 more times, and the header appears in the file 4 times. I feel like I'm misunderstanding something - does this mean the entire firmware file is only 1MB?
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By eriksl
#82826 How about you're seeing remaining parts of code that has been flashed earlier? Flashing of the ESP8266 doesn't erase all of the flash, that would be unnecessary and harmful to the flash.

Another explanation would be that your ESP has had a multi-slotted firmware at one time.