Here we have a very quick look at the Core i7-7800X, in the proverbial flesh. Both top and underside are similar in appearance to its Broadwell-E predecessor, to the extent that without the SKU code on the front it would be difficult to tell the difference between the generations visually. But dont take our word for it.
The Skylake-X CPUs packs in still more components to the underside of the CPU package, in keeping with the stark progression from Haswell-E to Broadwell-E. A few differences in pad layout may be enough to tip you off, but the different locations for those notches will ensure that you dont accidentally try to use the CPU in a motherboard for which it isnt intended.
The same appearance is expected for other Skylake-X CPUs up to the Core i9-7900X, but the jury it still out on the 12-core and greater models. An increased CPU die complexity of the on these designs may mean that the component and pad layout varies just slightly.