about the frequency.
in philips semiconductors datasheet ,power in 2.0V,25 degree the typ fmax is 30MHz.if in 3.3V power the fmax more then 30MHz.
what is "typ fmax" ,it means lots of this chip can reach parameter.
But strictly? power in 3.3V? the 74hc393 can not good work.
the best choose is 74vhc393 or 74lv393.
why did i choose 74hc393,because it is easy to buy and unexpensive.