BTW - I think this figure is wrong. I don't have copies of MPR handy to look at. Can you double check what it says (or did you already do that)?
Yes I looked it up. It is 12 more than Athlon. Of course MDR is occasionally wrong but in this case I know the 400 number is absolutely wrong. I looked at AMD's own presentations but they didn't provide this info.
Instructions in flight is listed as 72 for Opteron, which implies more rename registers than you quote.
There is a separate reg file for FPRs, 88 in Athlon so likely at least as many in Opteron. So your instructions in flight number likely includes all types not just int ALU ops.