Wireshark and single core CPU problem

Hi guys, i've installed on my old laptop a kali linux distro, it has a single core cpu, i'm trying to perform a arp poison + wireshark packets sniff, but when starting the arp poison script, in the wireshark gui i can't even select the interface to listen on because as i click on it, it deselect its self. It seems like while performing arp poisoning the interfaces appear busy to wireshark maybe due to my slow 1.6 ghz and single core cpu. i think it could be the cpu because when running only wireshark without any other tool it runs just like it should. So my question is, should I update my cpu because it's the main reason of the problem or it's just something else ? thank you for the help!!