The "Thorton" core was a variant of the "Barton" with half of the L2 cache disabled and thus functionally identical to the "Thoroughbred" core; the word "Thorton" is in fact a portmanteau of "Thoroughbred" and "Barton".
The "Thorton" core was a later variant of the "Barton" with half of the L2 cache disabled, and thus was functionally identical to the "Thoroughbred-B" core. The name "Thorton" is a portmanteau of "Thoroughbred" and "Barton".