The CPU can run, but at a slower speed. It’s designed for a speed of 1.92 GHz using an FSB speed of 333. So in that case it’ll run at a speed of 1.5 GHz (using an FSB of 266). A CPU usually runs stable if it runs on or lower than the stock clock speed, so that should be fine. So on your motherboard, it’ll run at about 79% of the stock clock speed.
Yes, the 512kb one will be faster because it can store twice as much instructions in the cache. You can expect slightly better performance, but It’ll mostly be an improvement in numbers only
I would also like to add something on this theme. What is the FSB of the Phenom II X4 955@ 3.2, I’m hoping its 1333mhz becuase thats the ram speed i’m looking at purchasing