Different memory usage in identical devices

[devnull]

Can't figure this out, I have 2 identical ESP12/8266 devices and have disabled boot.py and main.py and when I compare the memory usage of both devices they are different, one has about 5% less available than the other.

This is resulting in one of them not being able to run code that the other one can.

Immediately after reboot, they appear to be the same, but when I import a frozen file (import sh) which is identical on both systems, the available ram on 1 device is 5% less than the other one !

Can anyone suggest why this might be ?? - I have verified this several times.

Also, what do the various chars "=ABh." mean in the memory map ?

First Device

Code: Select all

>>> import micropython
>>> micropython.mem_info(1)
stack: 2144 out of 8192
GC: total: 36288, used: 5072, free: 31216
 No. of 1-blocks: 17, 2-blocks: 7, max blk sz: 263, max free sz: 1942
GC memory layout; from 3ffef2c0:
00000: h=AhhBMh=Dh=hDhB=BBBh===h====ABhhh==h===========================
00400: ================================================================
00800: ================================================================
00c00: ================================================================
01000: ===========================================h==h===h===h=B.....h=
01400: ....h=..........................................................
       (29 lines all free)
08c00: ............................
>>> import sh
>>> micropython.mem_info(1)
stack: 2144 out of 8192
GC: total: 36288, used: 12080, free: 24208
 No. of 1-blocks: 113, 2-blocks: 28, max blk sz: 263, max free sz: 1504
GC memory layout; from 3ffef2c0:
00000: h=hhhhMh=Dh=hDhB=BBBh===h====h==hh==h===========================
00400: ================================================================
00800: ================================================================
00c00: ================================================================
01000: ===========================================h=hhh=hhhhSh=hhBhAhh=
01400: =hhMhhDBh=h=BDBBBh=================h==h==hh=h=======h===========
01800: ================================================================
01c00: ================================================================
02000: ===============hhh=hhhh==hh====hhh=hhhh==hh======hhh=h======h===
02400: ====h==hhh==hh=hhh=hhhh==hh=hh============Shh=hhhh====hhh=hDhhhh
02800: ======hh===Shhh=BABBDBBh===h=h===BDBBh=h===BDTBh=B=h===BDBBhh=h=
02c00: ==BDBBh=h===hhhhhhh=h===TB=BBh===B.........h=h==============....
       (23 lines all free)
08c00: ............................
>>> 

Second Device

Code: Select all

>>> import micropython
>>> micropython.mem_info(1)
stack: 2144 out of 8192
GC: total: 36288, used: 5072, free: 31216
 No. of 1-blocks: 17, 2-blocks: 7, max blk sz: 263, max free sz: 1942
GC memory layout; from 3ffef2b0:
00000: h=AhhBMh=Dh=hDhB=BBBh===h====ABhhh==h===========================
00400: ================================================================
00800: ================================================================
00c00: ================================================================
01000: ===========================================h==h===h===h=B.....h=
01400: ....h=..........................................................
       (29 lines all free)
08c00: ............................
>>> import sh
>>> micropython.mem_info(1)
stack: 2144 out of 8192
GC: total: 36288, used: 10880, free: 25408
 No. of 1-blocks: 112, 2-blocks: 28, max blk sz: 263, max free sz: 1579
GC memory layout; from 3ffef2b0:
00000: h=hhhhMh=Dh=hDhB=BBBh===h====h=hhh==h===========================
00400: ================================================================
00800: ================================================================
00c00: ================================================================
01000: ===========================================h=hhh==hh=hh=hhBh=hhh
01400: hhhMh=DBShh=BDBBBh=================hh=======h=======h===========
01800: ================================================================
01c00: =====h==h==h=hhh=hhhh==hh====hhh=hhhh==hh======hhh=hhhh==hh=hhh=
02000: =====hhShhh==hh==h==h============h=hhhh====hhh=hDhhhh======hh===
02400: Shhh=BABBDBBh===h=h===BDBBh=h===BDTBh=B=h===BDBBhh=h===BDBBh=h==
02800: =hhhhhhh=h===TB=BBh===B.........h=h==============...............
       (24 lines all free)
08c00: ............................
>>> 

[dhylands]

See this thread:
viewtopic.php?f=2&t=3287
for a discussion of interpreting the mem_info output.

[Damien]

The firmware on the 2 devices are not identical. The heap on the second one starts 16 bytes later in RAM. See the 3ffef2c0 vs 3ffef2b0 numbers.

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