Understanding how the iMac stacks up against the MacBook Pro requires two comparisons in one. First, there's the general issue of the differences between the Core i5 and the Core i7 processors. Then, there's the difference between the specific i5 and i7 models available. The bottom line is that iMacs, whatever their processor, generally outperform even the fastest MacBook Pros. This is because, as laptops, MacBook Pros lack the space necessary for the larger cooling systems that the fastest i5s and i7s require. However, some MacBook Pros come very close to performing on par with lower-level iMacs.
Threads are instructions that running programs command processors to carry out. Generally, a processor can only work on as many threads as it has cores. For instance, a dual-core i5 processor can handle two threads at a time, while a quad-core i5 can handle four. However, Core i7s include hyperthreading technology. This means they can handle two threads simultaneously per core. Thus, a dual-core i7 can handle eight threads. Applications written to take advantage of hyperthreading run more quickly on a Core i7 than on an i5, all other things being equal.
Cache is a form of memory located on the processor itself. As such it can deliver information more quickly than RAM. Both i5 and i7 processors use cache to store frequently used information. This saves them from having to wait for the data from the slower RAM every time they need it. The primary difference between the i5 and the i7 is that i7s contain more cache.
Core i5 Options
As of summer 2011 Apple provides three i5 options for the iMac. All of them have four cores and 6MB of cache. They differ only in terms of speed; 2.5, 2.7, and 3.1GHz, respectively. There is only one i5 option available for the MacBook Pro. This is a 2.3GHz dual-core with 3MB of cache. Here, the iMac processors are superior in every way. Even the slowest i5 iMac will boot faster, run applications more quickly and run more programs simultaneously without a drop in performance than the i5 MacBook Pro.
Core i7 Options
There are two i7 options for the iMac. Both are quad-cores, and both have 8MB of cache. However one runs at 2.8GHz, while the other runs at 3.4GHz. MacBook Pros can have one of four i7 configurations. The fastest runs at 2.7GHz but only has two cores and 4MB of cache. All the others are quad-cores. One runs at 2.3GHz with 8MB of cache. The others run at 2.0 and 2.2GHz and have 6MB of cache. While non of these can outperform even the slowest i7 iMac, the 2.3GHz i7 MacBook Pro will perform on par with the 2.5GHz i5 iMac, as it os very close in speed, has the same number of cores and has 2MB more cache memory.
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- Apple: MacBook Pro 17-inch Technical Specifications
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