How is flash speed set

[eyal]

I have a few esp-07 (512KB flash) and esp-12 (4MB flash). The former run fast while the latter are slow - consistently. The difference is drastic, for example using nodemcu-firmware (lua) compiling my modules takes about 1s on the esp-07 and about 6s on the esp-12. Formatting the fs takes less than 1s on the esp-07 but 35s on the esp-12.

All the modules report a 40MHz speed and quad i/o capability.

How is flash access set? Is it done by the sdk when it boots up or is it fixed and stored somewhere in the flash? This is critical as the esp-12 uses about 4 times as much power as the esp-07 to run my application.

TIA