Haswell-Y isn't really suitable for a tablet imho. The base clock in LFM (SDP) mode is pretty low to achieve 6W or 4.5W SDP and it has only two cores.
The promise of the Y processor isn't just the lower TDP cap. It's the fact that the thermal control mechanism has the precision to run at multi-GHz speeds for brief amounts of time, giving you nearly the same performance as the 15W products, for most real-world operations. Think about it for a second. Most real work - such as loading a web page, or running an Excel macro, a Photoshop filter, ripping an mp3, etc - all take seconds to accomplish before the CPU returns to idle. During that time, these processors run at multi-GHz speeds, giving you the responsiveness of a higher performance CPU.
By the way, this same trick is how Snapdragon 800, Tegra 4, and Exynos 5410 all post record benchmarks, when in reality they would throttle just as much if the tiny little Android benchmarks were to be run in a loop enough times.
And don't worry about "just two cores". It's plenty. The same number of cores power most Core i7 laptops that end up with performance about 5 times faster than quad core ARM SOCs. I think Haswell "Y" will thoroughly embarrass the ARM SOCs in any workload scenario that doesn't aim for a long steady-state testing period.
Though at some point, capping the power at 4.5W or 6W is going to mean it has to run in LFM. For some things, it won't be well suited (i.e. don't try running Crysis or SPECfp_rate) - but for tablet workloads, it will kick butt and run circles around the ARM SOCs. Much to the contrary of your initial claim, Haswell Y is "perfect" for a tablet.
Market Data 
Markets 
AI
