According to Kodak's website, 12-1/2 minutes. The page with the development chart for TMX and TMY in Kodak's developers is at:(posted 9294 days ago)http://www.kodak.com/cluster/global/en/professional/support/techPubs/f 32/f32b.shtml#051
I've used Kodak's time for TMX (100) in D-76 1:1 with good results, so this is probably a good place to start. (And in a bizarre little coincidence, I just loaded my first roll ever of TMY [400] in my Olympus Pen half-frame camera yesterday... and I intend to develop it in D-76 1:1 when it's finished!)