In our recent group test of 37 Haswell motherboards MSI's most high-end motherboard wasn't included. We've since had the opportunity to test the MSI Z87 XPower, a motherboard that's aimed at the most avid overclockers out there. We compared it to the motherboards we tried out earlier.
The XPower is positioned above the MPower and MPower Max motherboards from MSI, and its lineage is obvious, with the yellow and black colour scheme indicating that it's meant for serious overclockers. We'd argue that for motherboards in this price segment looks do indeed matter, and MSI has definitely succeeded in that department with the design and colour combination.
The MPower and MPower Max boards are also built for overclockers, but the XPower really begs to be used with phase-change or LN2. The board is supposed to be able to supply up to 1,920 watts of power to the CPU. That's just in theory, because MSI's own tests show that a Core i7 4770K Haswell CPU at 3.5, 4.4, 5.0 and 6.0GHz draws 100, 150, 250 and 500 watts, respectively.
When you compare the MPower Max to the XPower (click here for a comparison table) there are a number of differences. The XPower has more PCI-Express x16 slots, five instead of three. Four of them are connected to a PLX PEX8647 'lane duplicator' chip, which makes it possible to have two graphics card with 16 lanes each or four GPUs with eight lanes each. Unlike the other board, the XPower supports 4-way SLI. The fifth slot (physically the second) is connected directly to the CPU, circumventing the PLX chip. That's to prevent the very minor latency, which overclockers will appreciate. It could get you those extra few points in 3DMark. So you can either use a combination of slot 1, 3, 4 and 5, or slot 2 if you only have one graphics card. You can read the rest of MSI Z87 XPower preview on Hardware.info.