Different CPU overload depending of which audio card I use

[jimax]

Hello guys
I sharing with you a bad experience with my setup.
Using Protools 12 with a RME Hdspe fx Madi card and 2 SPL Madison converters. I had that problem already when I was on PT 11, but didn't test with othet soundcards.

I cannot go under buffer size of 128 for recording with no cpu overload. Recording at 44.1k 24 bit on a 7.200 tr dedicated HD.

I tried with a Universal Audio Apollo FireWire Quad and can go at 64.

I even tried with the built in audio sound card of my Mac Pro mid 2012 and was able to work at buffer 32 !!

Already tried to turn off all the app in background / upadte system / re install protools.

It serms to be an hardware problem. Should my Rme madi pci card be broken ? Appart of the Cpu cliping if using very low buffer, no problem at all.

Whats the problem ?!