Several readers have been considering the purchase of new high-end models of iMac, especially interested by the Quad Core CPU, aka Core i5 or i7. It also shows that one should not based its analysis only on the clock speed and one should look beyond figures. IT will be difficult to provide a definitive answer as by definition software solution evolves and what was true yesterday might be wrong at the end of the week. NEvertheless it is a good time to provide some additional information regarding the TurboBoost mode available only on Core i5 and i7. Intel is now calculating performance of its processor based on their thermal envelop and control. In other mode, if thermal specifications are respected, then the CPU could be overclocked to respond to a peak of requests. This is a dynamic system. Some examples:
- The Core i5 offer 4 cores clocked at 2.66 GHz. Depending on working load, this CPU can on-the-fly overclock its all 4 cores to 2.8 GHz. If the application required only 3 CPU, they could be overclocked at 2.8 GHz too. If you are running a mono or double threaded application, then the CPU will be able to overclock one or two cores to 3.2 GHz.
- For the Core i7 also available at 2.8 GHz, it can ramp up to 2.93 GHz with 3 or 4 cores. If only 2 cores are used, the clock speed could reach 3.33 GHz, and if you are using a mono-threaded application, it will jump to 3.46 GHz.
So, despite lower than initially thought clock speed, Core i5 or i7 iMac could provide a serious gain of performance, and one should look carefully of the type of application being used before choosing a CPU able or not to dynamically changed its clock speed according to needs. You can consider that the Core i5 or i7 will never be slower than the current Core 2 Duo. In addition, you should also remember than the Core i7 support hyperthreading, so it offers 8 logical cores, making multi-CPU aware applications able to benefit from such raw power.
