Skylake: Intel Core i7-6700K

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Skylake: Intel Core i7-6700K

September 14, 2015 by Lawrence Lee

Product
Intel Core i7-6700K
LGA1151 Processor
Manufacturer
Street Price
US$350

Since the launch of Sandy Bridge in 2011, Intel's tick-tock microprocessor architecture upgrade cycle has been decidedly light on the tock, the distinctive thump corresponding to a more substantial update than the quieter tick preceding it. Despite the die shrink from 32nm to 22nm, Ivy Bridge represented a fairly minor upgrade in performance and efficiency. Its successor, Haswell necessitated a socket change but the level of improvement was more or less the same. The subsequent tick, Broadwell, was even more disappointing as it focused on the low-end embedded/mobile market.

"K" Chips Comparison (Haswell vs. Skylake)
Model
i5-4670K
i5-4690K
i5-6600K
i7-4770K
i7-4790K
i7-6700K
Socket
LGA1150
LGA1150
LGA1151
LGA1150
LGA1150
LGA1151
Memory Support
DDR3
DDR3
DDR3L
DDR4
DDR3
DDR3
DDR3L
DDR4
Cores / Threads
4 / 4
4 / 4
4 / 4
4 / 8
4 / 8
4 / 8
CPU Clock (Base/Turbo)
3.4 / 3.8 GHz
3.5 / 3.9 GHz
3.5 / 3.9 GHz
3.5 / 3.9 GHz
4.0 / 4.4 GHz
4.0 / 4.2 GHz
L3 Cache
6MB
6MB
6MB
8MB
8MB
8MB
Graphics
HD 4600
HD 4600
HD 530
HD 4600
HD 4600
HD 530
Execution Units
20
20
24
20
20
24
Max GPU Clock
1200 MHz
1200 MHz
1150 MHz
1250 MHz
1250 MHz
1150 MHz
TDP
84W
88W
91W
84W
88W
91W
Price (USD)
$230
$230
$240
$330
$300
$350

Skylake is the codename for this year's tock, built on the same 14 nm process as Broadwell, but offered to mainstream desktop users in a new socket with an extra pin, LGA1151. For the initial launch, Intel has chosen to put its best foot forward, presenting a pair of "K" series chips with unlocked multipliers aimed at enthusiasts first and foremost. As usual, the differentiation between Core i7's and i5's is the presence of Hyper-threading and the amount of L3 cache. The i5-6600K appears to be the direct analog of the popular i5-4690K while the i7-6700K is similar to the i7-4790K, except for an unusually low Turbo Boost of just 200 MHz.

The new processors are 91W parts, slightly higher than the last generation, possibly due to the upgraded integrated graphics. Intel Graphics HD 530, the successor to HD 4600, should deliver a noticeable performance increase despite having a slightly lower maximum clock speed. It's equipped with an additional four execution units, and in all likelihood, will be paired with faster DDR4 memory. For Skylake motherboard makers have the choice between dual channel DDR4 and DDR3L memory. Standard DDR3 is not officially supported as its voltage range is higher but there are a handful of models offering the regular standard.

Under the hood, the biggest change is the removal of the integrated voltage regulator, which improved efficiency and lowered costs but ultimately generated too much heat at high clock speeds, limiting the overclockability of Haswell/Broadwell chips. For Skylake, the responsibility of voltage regulation is returned to the motherboard, reducing the thermal load placed on the processor itself. The integrated graphics also now offers hardware decoding for the new HEVC/H.265 video codec as well as encoding through Intel's Quick Sync feature.


Z170 chipset block diagram.

With this release, you can expect another slate of chipsets, designated the 100 series by Intel, with the Z170 as the flagship. The main improvement over Z97 is faster DMI 3.0 interface between the chipset and processor, a modest increase in native USB 3.0 ports, and a large surplus of PCI Express 3.0 lanes which will be primarily utilized to facilitate faster storage and interface options.

Windows 7 users should take note that EHCI (Enhanced Host Controller Interface) has been dropped, a feature required for installing the O/S from a USB key. Windows 8 and 10 support USB installation through xHCI, so there are no issues there. If you're not ready to move on to Microsoft's newer operating systems, a fresh install of Windows 7 must be performed from a DVD, and during the install no USB interface devices will be usable, so a PS/2 keyboard will also be required (assuming the board even offers one).


Our Core i7-6700K sample.

The Gigabyte Z170X-UD5.

The motherboard for this review, the Gigabyte Z170X-UD5 takes advantage of the added PCI-E lanes, sporting two M.2 slots, three SATA Express ports, and a USB 3.1 controller with both a 3.1 and Type-C connector at the back. Rounding out the main features of this US$190 ATX model is support for 64GB of DDR4 (running up to 3466 MHz via overclocking), three PCI-E x16 3.0 slots supporting 3-way CrossFire and 2-way SLI, and an ASMedia SATA chip bringing up the total number of SATA 6 Gbps ports from six to eight.

While the socket is new, it uses the same mounting hole spacing as the rest as previous LGA115x platforms so aftermarket heatsink compatibility is preserved.



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