If the information
in what appears to be a slide from Intel is indeed correct, then the X48 chipset looks to have a lot of limitations that weren't expected. However, we know that some of the information isn't correct, as the slide states that the X48 chipset doesn't support DDR2, although we know that there are motherboard manufacturers working on DDR2-based X48 boards.
The interesting part here is the fact that the slide claims that the X48 chipset can only use one DDR3-1600 DIMM per channel, which seems strange. It also mentions that the memory voltage has to be 1.8V, instead of the standard 1.5V, for DDR3 memory if DDR3-1600 modules are going to be used.
But worst of all is the fact that it seems that DDR3-1600 will only work with 1600 or 1066MHz FSB, with no support for 1333MHz bus CPUs. This seems a bit of a problem for Intel, since those with 1333MHz FSB processors won't be able to use this chipset with fast DDR3 memory.
You can find the slide here