| rax | 241 | set CPU-Core to use | 8 bit |
| rbx | pid | process identifire 0 for this calling process | 32 bit |
| rcx | cpumask | cpumask *in_mask, core=processor bits | n*32 bit |
| On return | rax |
| 0/errorcode |
| Errorcode | c++ name | Description |
| 1 | EPERM | Operation not permitted |
| 3 | ESRCH | No such process |
| 14 | EFAULT | Bad address |
| 22 | EINVAL | Invalid argument |