This is an optional exercise. You will learn more tricks of NAMD.
Use the tau value you are assigned in the NAMD input file echo.conf:

set tau 200	   ;# here you want to assign your tau value

Reassign the initial velocity according to 300K, 

set temperature     300
temperature         $temperature

Now you need to save this initial velocity distribution to a file
of so-called 300.vel, so that it can be used as input file for the
next simulation. To do so, use:

run 0

This command doesn't really run any simulation, but just initialize
the system. You can then save it as:

output	300

where 300 is the name for output.
After that, the simulation will run for tau time steps.

Get the temperature data by typing:

gettemp youroutputfile > temp2.dat
