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Intel Core i9-7900X X-Series Skylake-X CPU Review (Page 2)

By Steven Bassiri from Jun 19, 2017 @ 8:01 CDT
TweakTown Rating: 92%Manufacturer: Intel



The top of the CPU features a very large heat spreader like the one Broadwell-E used. The bottom is where we find the pads that fit into the LGA2066 socket. The new socket's mounting hardware allows for the use of LGA-2011 heat sink coolers; we are glad Intel decided not to change the cooler mounting.


To Skylake-X does have a chip on it labeled "642 X8", and it is a RFID tag. However, Intel confirms that is does nothing on consumer SKUs; it's just a holdover from the fact that Skylake-X CPUs are from the top of the stack, meaning they are lower-end equivalents of their Xeon counterparts.

New Additions


Skylake-X uses the Skylake microarchitecture, which is pretty much the same as the Kaby Lake architecture. However, while Kaby Lake-X is basically a transplant of its Z270 counterpart, Skylake-X is not. It has a few changes, but the core microarchitecture remains the same.

It has an improved front-end and increased bandwidth, but we have known this since Skylake launched over a year ago, so the slides above are just a rehash of the changes made in Skylake over Haswell. At the time, Intel called it their "Best CPU Ever," and it did provide roughly 7% IPC increase over Haswell.


Intel rebalanced the cache hierarchy, and now the L3 cache, which is half the size it was in the previous generation, acts as a victim cache and is filled with evictions from the L2 cache (which is private to each core). The L2 cache is quadruple the size it was in previous generations, bringing cache closer to each core. Intel has also shifted to a mesh architecture from a ring.

CPU interconnect layout is very important, and it can also account for anywhere from 15-30% of the CPU's power budget. The reason for this shift was not only to facilitate better interconnects for higher core count CPUs but also perhaps because of this change in cache policy and distribution.


AVX512 has also been added to Skylake-X, and the new library offers many different optimizations along with some very useful instructions that can be easily taken advantage of to improve performance. The types of optimizations are especially useful in workstation and above applications, which is one of the targets of the Skylake-X line of processors.

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