Questions about Pistachio

[Gregory]

so far, i have figured out the problem with the interrupt problem, but 
i cannot seem to acknowledge the interrupt after i have received it. 
The problem apparently is that the MR0 doesn't seem to completely 
clear the 32nd bit always seem to be set. my code looks like this:

L4_LoadMR(0, 0);
L4_Send(root); //so i can actually see what value is sent out in the ipc

since we know there is no type or untyped words i simply check the 
label and i obtain this number :

decimal: 32768
binary: 1000000000000000

why is this so and how do i completely zero MR0?