I have just dug out my old Canon 35mm EOS with a Tokina lens AT-X 24-200.
I didn't expect it to work but gave it a whirl on the EOS 40D and it puts up Error 1.
After much searching I cant find where I could send it for a Re-chip if its worth the bother and expense or even if it can be done.
I had no problem with Sigma lenses.
I believe it would increase to 38x320. X-1.6