I am trying to compare the methods mentioned by Peter Cordes in

You can see that for the 32 nops, the predecoder requires 8 cycles, and for the remaining instructions, it requires 5 cycles, which together corresponds to the 13 cycles that you measured.

You may notice that in some cycles, only a small number of instructions is predecoded; for example, in the fourth cycle, only one instruction is predecoded. This is because the predecoder works on aligned 16-byte blocks, and it can handle at most five instructions per cycle (note that some sources incorrectly claim that it can handle 6 instructions per cycle). You can find more details on the predecoder, for example how it handles instructions that cross a 16-byte boundary, in you can see that the instructions after the nops now require 6 instead of 5 cycles to be predecoded, which is because several of the instructions in g1b are longer than the corresponding ones in g1a.