Choose About This Mac from the Apple () menu in the upper-left menu bar
Note the Processor ( Intel ____ )
| Processor Name | 32- or 64-bit |
| Intel Core Solo | 32 bit |
| Intel Core Duo | 32 bit |
| Intel Core 2 Duo | 64 bit |
| Intel Quad-Core Xeon | 64 bit |
| Dual-Core Intel Xeon | 64 bit |
| Quad-Core Intel Xeon | 64 bit |
| Core i3 | 64 bit |
| Core i5 | 64 bit |
| Core i7 | 64 bit |