Intel's Core i7 notebook chips may all consume too much power to be used in anything but high-end notebooks, a late leak indicates. Also known as Clarksfield, the 1.6GHz and 1.73GHz quad-core parts were originally thought to use 35W of peak power, suitable for average and some thin-and-light notebooks, but are now estimated to use 45W and would be ruled out for all but larger, desktop replacement notebooks. The flagship 2GHz Core i7 Extreme would be even more demanding at 55W.
The power draw would be at least a 10W difference over Core 2 mobile chips, which even in quad-core form normally top out at 45W or less and with higher clock speeds. An explanation isn't directly available, but the difference may stem from the complexity of the processors, which integrate their own memory controllers and support features absent from Core 2, like Hyperthreading.
If borne out, Clarksfield may not be ready to use for most notebooks if it launches as rumored later this summer. Instead, the first portable Nehalem CPUs likely to be commonplace should be part of the Arrandale family, a dual-core design that will also use a smaller, more power-efficient 32 nanometer assembly process.