Intel® Core™2 Extreme Processor QX6800 (8M Cache, 2.93 GHz, 1066 MHz FSB)
for detail http://ark.intel.com/products/30720
its best processor for DELL Optiplex GX620 because Optiplex GX620 use
Intel® 945G Express Chipset with Max
| Supported FSBs | 1066MHz |
more chipset detail http://ark.intel.com/products/27720/Intel-82945G-Memory-Controller