A new chipset: the Z170
One of the biggest changes from Skylake to Haswell happens at the platform level with the introduction of the new 100-series chipsets. By "chipset," I mean "companion I/O chip," since Intel's platforms have consolidated things into a single chip for several generations.
Skylake's companion chip is built using Intel's 22-nm fab process, and the enthusiast-class variant of it is called the Z170. This chip supports 26 high-speed I/O ports, each one offering bandwidth equivalent to a single lane of PCI Express Gen3 connectivity. That's a huge upgrade from the eight PCIe Gen2 lanes in the Z97 chipset. The Z170's high-speed ports can be deployed by motherboard makers in various configurations. The possibilities include up to 20 PCIe Gen3 lanes, up to 10 USB 3.0 connections, and up to six SATA 6Gbps ports—though not all at the same time, since there are 26 high-speed ports in total.
The tremendous bandwidth available via the Z170 prompted Intel to upgrade the DMI link between the CPU and the chipset, as well. The new DMI 3 link offers bandwidth equivalent to four lanes of PCIe Gen3. That's not nearly enough to sustain simultaneous I/O operations across all 26 of the Z170's high-speed ports. Heck, it's not even close, which is kind of a big deal since the system's memory sits beyond that DMI link, hanging off of the CPU's integrated memory controller. If this were a server architecture, I'd be worried about that fact. For typical desktop PC use, though, I suspect DMI's new four-lane arrangement should generally be sufficient.
Although the Z170 doesn't natively support the higher-bandwidth USB 3.1 standard, Intel offers a chip code-named Alpine Ridge that supplies both USB 3.1 and Thunderbolt capabilities, and several motherboard makers are adopting it. As a result, you can expect to see quite a few Skylake boards with USB 3.1 support. A subset of those should be qualified to work with Thunderbolt, as well.
Desktop Broadwell caches in
I mentioned the desktop variant of Broadwell earlier, and here is the fastest model: the Core i7-5775C. This is a four-core, eight-thread desktop processor with 6MB of L3 cache, and like all Broadwell chips, it's built on Intel's latest 14-nm process. With only a 65W TDP, the 5775C isn't a speed demon; its base and peak clocks are 3.3 and 3.7GHz.
This poor devil has led a neglected life. Intel unveiled it at Computex in June, but we didn't get a review sample for weeks. Then our review unit sat for a while in Damage Labs, untouched, while I labored away on Radeon Fury reviews. Meanwhile, these chips still aren't broadly available in North America, and now the new hotness of Skylake has arrived.
Regardless, the 5775C is intriguing for several reasons. First, it drops into existing Z97 motherboards and could be an upgrade option for current Haswell owners. Second, it has built-in Iris Pro graphics, which are pretty potent as these things go. As a 65W chip with an integrated GPU, the 5775C could fulfill some unique missions. Last and definitely not least, the 5775C has 128MB of eDRAM situated in a separate chip on the CPU package. This eDRAM helps to accelerate the Iris Pro graphics core, but it's also just a big frickin' L4 cache for the entire CPU. Any application whose working data set will fit into a 128MB cache could stand to benefit from its presence. We saw hints of greatness from a similar chip with an eDRAM cache back when we reviewed the first Haswells, but we weren't able to use it with a discrete GPU. The 5775C has no such limitations, and you may be surprised by its performance.
One qualifier, though: you will pay for the privilege of owning a 5775C. The current list price is $366, 27 bucks more than a Skylake 6700K. Assuming you can find one in stock.
Since we have a Haswell, Broadwell, and Skylake on hand, and since Windows 10 is out, I figured we should test a whole range of Intel processors against one another—so that's just we did, spanning five generations back to Sandy Bridge.
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