We have noticed that the ongame poker client uses a huge amount of CPU. After testing several skins, the problem seemed to occur on every poker client of any ongame skin.

Searching the internet and testing different setups, it turns out that the holdem manager hud was the main problem. As soon as we shut down holdem manager, the performance of the client drastically increased and the cpu usage dropped. Of course, not running holdem manager is not a solution.

There is a better solution to solve the cpu hog of the ongame poker client:
turn of the option 'Pop table on Action' in the poker client settings.

The underlying problem has something to do with the interaction of the hud and the poping tables. The huds detects what table is visible so the statistics can be drawn.

After turning of the table popup option, multitabling should be possible again. Of course, this is just a workaround for this cpu bug. It should be fixed by ongame so that tables with an action can popup, with a hud, even for multitablers. Without any performance issues.