Calculating flash size

[geo.espressif]

Could someone explain the flash size characteristics of the ESP8266. So, I can see when I flash that it is detected as an '8MBit flash', which is indicated as '512KB + 512KB' using the flash tool in info when you hover over. This is also alluded to in the 1.4 SDK by the "512+512" folder containing 'user1.1024.new.2.bin'.

So the question is more specifically:

- What do the two parts '512' represent?
- Why don't they add up to 8MBit?
- What is the actual maximum flash size of an image I generate?

I might have missed a section in some document so please do refer if appropriate. Many thanks!

James

[blubb]

2 * 512 kB == 1024 kB == 1 MB == 8 MBit

[geo.espressif]

Yeah got that, but why are there two? e.g. does my flash image have a maximum size of 512 or 1024?

[blubb]

The OTA feature uses two images. While one is running, the other one can be flashed safely.

If you do not need OTA flashing, you can use the whole space for a single image.

This is all explained in the pdf files.