LILYGO® TTGO T-Display ESP32 4M available RAM less than expected

[robertoseno]

CircuitPython version

Adadruit Circuitpython 9.2.1. Board LILYGO® TTGO T-Display ESP32 4M

Code/REPL

import gc
print(gc.mem_free())

Behavior

116768

Description

Despite the available amount of ram ( 520kB) with circuitpython the available ram is just 116768 kB (~22%). It seems a little weird to me as other boards like adafruit feather nrf52840 or raspberry pico w, with less than 300kB of ram, both show 137kB (>50%) of available ram in circuitpython.

I don't know if this gap, 23% (esp32) vs 50% (nrf52 or rp2040), is due to the different architectures or to something else but the lower amount of available ram on TTGO seems akward.

Additional information

No response

[dhalbert]

See https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/memory-types.html. The 520kB of RAM is not uniform but is divided up into different areas with different possible uses. E.g. one example of that from that page:

There is 520 KB of available SRAM (320 KB of DRAM and 200 KB of IRAM) on the ESP32. However, due to a technical limitation, the maximum statically allocated DRAM usage is 160 KB. The remaining 160 KB (for a total of 320 KB of DRAM) can only be allocated at runtime as heap.

[robertoseno]

Thank you very much for the explanation.