You mean the i7 920? It will be plenty for a 7870 in most games. Extreme cases like hectic firefights in BF3 multiplayer will bog it down, but in general it won't be an issue. Most games don't need very much CPU power, and any old quad core will do, or even a good dual core from the last year or so.
My old Xeon X3210 wasn't slow enough to bottlneck most games, even at its stock speed of 2.13 GHz.
yeah most games your sit, some rts games my cuase a slow down but nothing manageable
wow willard, is that your everyday clock speed