Assassin's Creed Steam auto patching

[titaniumx3]

Is there anyway to stop Steam from automatically patching Assassin's Creed when you install it? How do I know whether or not it's been patched?

I'd like to see what difference the DX10.1 feature makes before it was patched out.

Thanks!

 

[Gimpymoo]

The version you download will be "pre patched".