提高NIOS频率的技巧：
Turning on some optimizations in Quartus II may help increase it. Here are some you may want to try:
a.) Change the optimization technique to Speed
• Click Assignments -> Settings
• Select Analysis & Synthesis Settings
• For Optimization Technique, select Speed
b.) Turn on one-hot state machine processing
• Click Assignments -> Settings
• Select Analysis & Synthesis Settings
• For State Machine Processing, select One-Hot
c.) Turn off Multiplexer Restructuring
• Click Assignments -> Settings
• Select Analysis & Synthesis Settings
• For Restructure Multiplexers, select Off
d.) Turn on Physical Synthesis in the Fitter
• Click Assignments -> Settings
• Expand Fitter Settings by clicking the + symbol next to it.
• Select Physical Synthesis Optimizations
• Check Perform physical synthesis for combinational logic
• Check Perform register duplication
• Check Perform register retiming
• Select Normal for Physical synthesis effort
