Closer Look at Intel P45
Even the block diagram shows that Intel P45 MCH (Memory Controller Hub) is a close relative of P35:
The only difference is the new PCI Express x16 2.0 graphics interface support. Just like in P35, it may be split between two graphics slots, each receiving 8 PCI Express lanes. As you know, only X38 and X48 support two complete PCI Express x16 2.0 busses. However, if you use two PCI Express x8 instead of PCI Express x16 for a dual-graphics card Crossfire configuration, it will not affect the performance that much. Especially since 8 PCI Express lanes supporting second version of the protocol provide the same bandwidth as PCI Express x16 1.0.
The new ICH10 South Bridge that replaced its predecessor, ICH9, is certainly very interesting. Especially, they will continue using it even in the post-P45 era, with the first Nehalem chipsets. However, bright future is probably the only thing it can actually boast. It even has the same pin layout as the old
As a result, if we compare the four discrete chipsets from Intel side by side, we will get a very strange picture:
Most users will consider the differences between these four chipsets to be of purely marketing nature. It is partially true. Moreover, all four chipsets works just fine with CPUs supporting 1600MHz bus and with DDR3-1600/1800/2000 SDRAM, despite the numbers listed in the official documentation. However, if we dig a little deeper, we will be able to see some completely different things:
Despite the fact that MCH is now manufactured with 65nm technology, P45 turns out a much hotter chipset than P35. It should be PCI Express 2.0 support that contributes to increased heat dissipation. That is why X38 and X48 are so warm that Intel tops them with a heat-spreader that neither P35 nor the new P45 have.