Max Speed for altshift_taps in a M9k

[Altera_Forum]

I'm trying to run an altshift_taps module at 400 MHz, but Quartus is telling me that it is restricted to 375MHz. My setup for the altshift_taps module is : M9K, 3 taps, tap distance 4, width 12 and a target device EP3SL150F1152C2. The datasheet for the EP3SL150 -2, indicates that TriMatrix memory can operate up to 600MHz, but the -I4 flavor is limited to 375MHz. Is there a glitch in Quartus mixing up the -2 & -I4 speed settings or is there truely a limit with the altshift_taps?

[Altera_Forum]

looks like there are a couple of modes where even the SIII -2 M9K runs at 375MHz if the read-during-write option is set to "Old Data". i'm not sure that altshift_taps should be using that mode, or how to tell that is it from a mapper or fitter report.