ESP8266 Memory Configuration

[P. Short]

Probably a dumb question, but how is the ESP8266 memory laid out, particularly in an OTA setup? My naive impression is that the code/data downloaded over the air ends up being initially stored in the external serial flash chip typically located on the 8266 module. Does the processor execute instructions from that memory (presumably with the aid of the CPU data/instruction cache)? It's also my understanding that the external serial flash chip is at least one order of magnitude slower than the internal CPU instruction memory, so any implementation must depend on good cache design to obtain any decent performance.

Is any of my code able to reside in the main CPU instruction memory along-side the OTA code, or is that memory completely dedicated to OTA functionality?

Where does 'my code' reside when I use the serial port to download code?

Thanks,

[P. Short]

Doing more searching, I'm beginning to wonder if I misunderstood things and that the ESP8266 has any internal program (flash) ROM at all, and if the only place that code is stored (apart from cache) is in the external serial flash chip.

[MartinMueller2003]

As far as I know, there is no internal flash. It is all external to the core.

[P. Short]

Thanks. I found most of the answers that I wanted in the Kolban book.