It keeps instruction sets. For maximum speed. Instead of doing this on the motherboard. Its on the cpu.
I take it you want this one. Because you have a motherboard that has a bios update. Then you wanted more "mhz" instead of the newer chip that your mobo supports.
Id take L3 cache over 200-400mhz anyday.
Then if you research. Youll see that the 9xx series. Has what that 840 has plus the L3.
A long time ago. When intel released their "extreme" chips. The cache was what made it faster.
Then Im pretty sure. Both are in same price range. Unless you have a stupid deal on the 840. Id get a 9xx one.
having L3 cache is better than having more ghz. one can always overclock a cpu to add more clockspeed, but not cache. L3 cache does have impact on cpu performance.