Processors are not usually measured in performance by how much cache they have.
Also, getting a virus is a user issue nowadays, not an OS problem. If you had decent anti virus software and took precautions, you won't get infected. I haven't gotten a virus on a personal PC of mine for at least 5 years (using Windows), and I am constantly torrenting, downloading porn etc. You need to not click on stupid shit.
Also if you run Windows on that Mac, you will get infected if you continue the same way you have. Running on Mac hardware will not magically make your Windows install invulnerable to infection.