VR Zone explains how Intel will recycle its "broken" Ivy Bridge chips, you can read it over here. The site claims this repurposing is part of the reason for the delay of some Ivy Bridge models.
Intel has no less than seven different configurations for its Ivy Bridge processors, of which what is known as the 4+2 and 4+1 models, will be part of the initial launch. A 4+2 is a quad core CPU with a GT2 graphics core and a 4+1 is as such a quad core CPU with a GT1 graphics core. However, to create a 4+1 model, Intel has two different options, it can either make a specific chip or it can "harvest" a slightly failed 4+2 part and turn it into a 4+1 part. In this case Intel has the option to use models with both damaged GPU cores and damages cache, as the 4+1 models in general has less cache than the 4+2 models. As an example, something like a failed Core i7-3770 could be turned into a Core i5-3570 by disabling half of the GPU execution units and 0.5MB of cache per CPU core.
Things get a little bit more complex when we're moving on to the dual core models, as here we have 2+2 and 2+1 models, but these can either be made as intended, or once again "harvested". In the case of the 2+2 model it could only come from a 4+2 model, but the 2+1 models can be from a 4+2, 4+1 or a 2+2 depending on demand. Intel's internal marker for the "harvested" models appears to be a capital F, as in 4+1F or 2+1F.