0 - 2 of 2 tags for swapping

How can I swap both column values using only update statement? No Alter table permitted.
Table: T1 
A B
1 2
3 4
5 6
 
After execution the table will look like:
Table: T1
A B
2 1
4 3
6 5

I was lucky enough to be able to attend Partners in San Diego last week.  As part of that, I did have an opportunity to speak a time or two and discussed a few performance issues.

I discussed swapping, SegIO Reads, and measuring I/O bandwidth but wasn't able to provide detail or queries, etc. at the time.

They are below.