Unlike the quad-core Intel i5 and i7 desktop processors found in the Apple iMac, the mobile i5s and i7s in the new 15 and 17-inch MacBook Pros are two core processors. Both include Intel’s Hyper-Threading technology, so both can run four virtual threads.

First, some background. In 2009, Apple introduced new iMacs with Intel’s i5 and i7 quad-core desktop processors. That i5 differs from the i7 in that the i7 has Hyper-Threading, the ability to run two virtual threads per core. As a result, the i5 iMac can run four threads and the i7 iMac can run eight. If you look at the technical specification page for the iMacs, Apple clearly spells out “quad core.”

On Tuesday, April 13, Apple introduced new MacBook Pros. The 15-inch and 17-inch models are available with Intel’s mobile i5 and i7 processors introduced in 2010. Both of these processors have two cores and both utilize Intel’s Hyper-threading technology. And they use a smaller, less power hungry 32 nanometer process. The tip-off is Apple’s technical specification page for the new 15 and 17-inch Macbook Pros which makes no mention of the term “quad-core.”

As a result, each of these two mobile processors can run four virtual threads. The only significant difference is that the i7 has sightly more L3 cache (4 vs. 3 MB) and can Turbo boost to a higher clock speed: the i5 at 2.4 boosts to 2.933 GHz and the i7 at 2.66 can burst to 3.333 GHz.

Apple and Intel likely chose this route for good reason. The desktop i5 utilizes a 45 nanometer process and generates 95 watts of heat. The big brother i7 generates 130 watts. That’s okay for a well cooled desktop iMac, but unsuitable for the smaller, mobile MacBook Pros with limited cooling power.

On the other hand, the mobile i5 and i7 generate about 35 watts of heat each, yet with Hyper-Threading can still launch four virtual threads. Thread-wise, that’s as good as a desktop i5 that doesn’t have Hyper-Threading.

While we’d all like to boast “quad-cores” in our new MacBook Pros, the route Intel and Apple have chosen leads to, as reports coming in suggest, pretty good performance with a lot less heat generation. For now, we’ll just have to boast “quad threads” in our MacBook Pros.