Find complete results of compilation with v2.6.0 here - I will remove it after a week.

Looking at 8052.mem reveals, that "data" area (DSEG) is filled up to 0x77, leaving 8 bytes in this segment.

Unfortunately, the .map nor .sym files are not very informative as long as automatic variables are concerned - i.e. space the compiler allocates to local variables when it cannot locate them to registers, and "spills", i.e. space for intermediate calculation results (again if they won't fit to registers). You have to go to .lst files, to the DSEG description, to have detailed information on these.

Now take the 2.9.x, cut down from the buff[] array (I simply decreased BUFFSIZE to 16+1, but I don't guarantee it will work), which is the single biggest variable in "data", and comparing the DSEG in .lst you can see, where the newer version "looses space". It's slightly more than the 8 bytes "spare".

JW