strange behaviour when using dictionary

Hi folks,
I am trying to use the cuda version of hashcat to hack a WPA/WPA2 cap file (from my own router). So I create a basic dictionary with 100 words amongst which is the password of the router. Then I try something like:
(the cap has been converted to hccap)

cudaHashcat64.exe -m 2500 output.hccap mydictionary.txt

goes through the dictionary and does not find anything.


Then I try

cudaHashcat64.exe -a3 -m 2500 output.hccap mydictionary.txt

and it works!!
But it is much slower and does not utilise all my GPUs. The first version is much faster and utilises all the GPUs.


BTW, aircrack-ng can perform the dictionary crack correctly.

Any ideas?

Thanks