Hey there,
Well that depends on what your definition of backwards is ........

Some people consider backwards upside down. J/K though

To tell the truth........it is possible with some heatsinks. Some just
won't fit if you try it and you could break the board or the HS.
This is definately a bad thing. The raised part of the bottom of the HS should
match up with the raised portion of the CPU socket.
That should help
Slade