Here are the controls that I use:

Keyboard:
cursor keys (forward,backwards,rotate left and right)
Ctrl,Alt (strafe left and right)
Space (Fire)
0/ins (Use)
Lshift (Speed)

  I'm running a Gateway 2000 486SX/33 w/8mg here at work and a Datel 486DX/33
at home. (.lmps were recorded at work :] )
 
  I really like the chainsaw. While I was recording E1M5 for this I tried
to finish with just the chainsaw from the time I got it. It was very difficult 
and so I decided to do it for my FREE.LMP.  The only thing I missed was the
short cut through the dark room at the end.  But, hey I was pretty much worn
out at that point and had killed every one, anyway you should try it sometime
The chainsaw has some peculiarities that make it very challenging to use.