Timing Not Being Constrained?

--- Quote Start ---

OK, I tried to post as little as possible since I didn't want it to get too complicated. The clock grouping goes;

set_clock_groups -asynchronous -group {real_clock}

set_clock_groups -asynchronous -group {real_clocka}

set_clock_groups -asynchronous -group {real_clockb}

There's no reference to the virtual clock in my grouping. What you're saying is perhaps that's the problem?

--- Quote End ---

Yes, that is the problem.

The first command sets all paths between real_clock and all other clocks as a false path.

The second and third to the same for real_clocka and real_clockb.

You probably need something like this

set_clock_groups -asynchronous -group {real_clock virtual_clock} -group {real_clocka} -groups {real_clockb}