126.96.36.199. Fast Input, Output, and Output Enable Registers
If the fast I/O setting is on, the register is always placed in the I/O element. If the fast I/O setting is off, the register is never placed in the I/O element. This is true even if the Optimize IOC Register Placement for Timing option is turned on. If there is no fast I/O assignment, the Intel® Quartus® Prime software determines whether to place registers in I/O elements if the Optimize IOC Register Placement for Timing option is turned on.
You can also use the four fast I/O options (Fast Input Register, Fast Output Register, Fast Output Enable Register, and Fast OCT Register) to override the location of a register that is in a Logic Lock region and force it into an I/O cell. If you apply this assignment to a register that feeds multiple pins, the Fitter duplicates the register and places it in all relevant I/O elements.
For more information about the Fast Input Register option, Fast Output Register option, Fast Output Enable Register option, and Fast OCT (on-chip termination) Register option, refer to Intel® Quartus® Prime Help.
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