[aseipp]

The ESP32 also uses an Xtensa, the LX6, which should have the same basic instruction encoding, etc (and I think they both use FreeRTOS, as well, but I only have an ESP32). Probably shouldn't be too hard. You can also stuff more functionality into it, too.[1]

[1] Related: I can't actually even find the documentation on what's precisely changed between the LX6 (ESP32) and the LX106 (ESP8266), other than the basics on the datasheets - I don't know of any documentation on e.g. any different architectural details. Maybe you have to ask Espressif. Or Cadence. Anyone have any idea?

[jakobdabo]

Their datasheets only mention the PIN definitions and electrical characteristics of the microcontrollers. Try to get the information from the reference manual[0]. Also there are these books[1][2] by Neil Kolban.

[0] https://www.espressif.com/sites/default/files/documentation/...

[1] https://leanpub.com/ESP8266_ESP32

[2] https://leanpub.com/kolban-ESP32

edit:

More information about the differences: http://www.cnx-software.com/2016/03/25/esp8266-and-esp32-dif...

[aseipp]

The ESP32 datasheet is really woefully inadequate for this part; it mostly describes the chip, but I guess what I'm really looking for is things like "A description of the ISA itself", i.e. the "LX6 datasheet", so to speak. So I want something like the the actual instruction encoding, instruction listing, etc for the LX6 series and what it supports precisely.

[MrBuddyCasino]

Most importantly, the ESP32 has register windows.

[aseipp]

Right, this is the kind of information I was looking for (maybe some actual ISA documentation; the instruction encoding method itself, etc).

But for this specific point -- I thought all of the Xtensa series used register windows? Or did they both have them but the ESP8266 never actually use them (somehow?)

[MrBuddyCasino]

The xtensa series is highly configurable, afaik the ESP8266 doesn't have them in hardware.

This is second hand knowledge though.