For AMX Mod X, we will be distributing a new hybrid compiler called AMXXSC.
Plugins compiled in this new compiler will be named ".amxx" instead of ".amx", although AMX Mod X can still read .amx files. This new format is for 64bit compatibility. 64bit AMX Mod X can only read the new format.
AMXXSC is a wrapper for dynamically linked versions of the Small 2.5.1 compiler, which is an unreleased version of 2.5.0 that has many bug fixes. This compiler is a hybrid of a 32bit compiler and a 64bit compiler, and outputs files in a new format called ABL (A
Abstract Ball is a format for storing multiple architectures of AMX plugins. It can hold the bytecode for 8, 16, 32, 64, 128, and 256 bit plugins. For AMX Mod X 0.20, the 32bit code is stored with compact encoding and the 64bit section is stored without compact encoding. Both sections are compressed with Lempel-Ziv-Oberhumer-1 compression.
For those interested, it is structured like this:
MAGIC (0x[RLEB]) [long/uint32]
# of Architectures [byte]
Stack size [long/uint32]
File offset [long/uint32]
LZO(CellBytecode) - 
Surprisingly, even though the amount of data is essentially doubled, plugins will often decrease in size under the new format.
The format for 0.20 versions >= TP3 is now "AMXBall". The magic is AMXB and the compression is gzip.