Tom's Hardware Writes:
"When Intel released its mainstream P45 Express chipset, the biggest news was that it supported PCI Express 2.0. Formerly available from Intel only on high-end X38 and X48 motherboards, many of us still failed to understand the significance of this bandwidth-doubling technology to current-generation hardware. After all, the first-generation x16 slots found on P35 Express motherboards are still fast enough for any graphics card, so why bother updating?
In order to truly understand how important PCI Express 2.0 is to the (upper) mainstream gaming market, one has to consider the P45 Express northbridge's other key feature: its ability to split those sixteen lanes into two x8 pathways.
The ability to run two PCI Express graphics cards in x8 mode hasn't been available from Intel since the days of its 975X chipset. Dual-graphics P965 and P35 motherboards usually relied on x4 pathways for the second slot, starving the second card with a lowly 2 GB/s transfer rate. By allowing its 16 PCI Express pathways to be divided into two x8-mode slots, the P45 Express can now deliver the same 8 GB/s bandwidth to two graphics cards that its P35 predecessor could deliver to only one.
Other updates to the P45 Express technology, such as the ability to support a total of 16GB RAM rather than the 8GB of the P35 Express, are far less significant to the majority of its mainstream/performance market."