SDC: forwarding clock with 90 degree offset

The reasons I can think of that might make it different.

- Logic on data path. (unlikely)

- IO registers not used. (pretty unlikely)

- Different globals used for the clock driving the data versus the clock. (I've sen this more than once)

- The IO delay chains are cranked up on the output path, or they have different I/O standards, one of which is much slower. If your data output is 4.449ns, what is the clock? In the fitter report, look at the IO Delay Chain Summary and see if the output chain is cranked up. This is usually due to I/O constraints that cause it to add delays. You would need to look at the hold analysis for this path too.