tpr file format
Description
The tpr file extension stands for portable binary run input file. This file 
contains  the starting structure of your simulation, the molecular topology 
and all the simulation parameters. Because this file is in binary format it 
cannot be read with a normal editor. To read a portable binary run input 
file type:
% gmxdump -s topol.tpr 
or if you're not such a fast reader:
% gmxdump -s topol.tpr | more
You can also compare two tpr files using:
gmxcheck -s1 top1 -s2 top2 | more