Tech preview: Intel Core i9 Skylake-X processors

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Core i9 and Core X series processors

Core i9 and Core X series processors

So Intel has now announced Skylake-X processors. Where the previous and current Broadwell-E platform had up-to 10 core processors (Core i7 6950X), Intel will expand on that with an up-to 18-core and thus 36-threads processor. Intel markets the news series are the Core X series, and also is adding a new denominator, the Core i9 series. The new processors are paired with a new chipset X299 and socket LGA2066.


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Kaby Lake

Broadwell-E

Kaby Lake-X

Skylake-X

CPU cores

4

6, 8, 10

4

6, 8, 10, 12, 14, 16

Cache

8MB

Up to 25MB

8MB

13.75MB

PCIe support

PCIe 3.0 (16 lanes)

PCIe 3.0 (40/28 lanes)

PCIe 3.0 (16 lanes)

PCIe 3.0 (44/28 lanes)

Integrated graphics

Yes

No

No

No

TDP

95W

140W

112W

140W

Socket

LGA 1151

LGA 2011-v3

LGA 2066

LGA 2066

Chipset

Z270

X99

X299

X299

Memory support

Dual-channel DDR4

Quad-channel DDR4

Dual DDR4

Quad-channel DDR4


Architecture changes

The new Core i9 series processors are based up-on the Skylake architecture that you know from the socket 1151 parts, but merely scaled upwards. The processor series is fabbed at 14nm. Despite being based upon the Skylake architecture, there are some changes to address. IPC has been improved meaning the number of instructions per clock-cycle have been improved. According to Intel, Skylake-X will see an up-to 8% perfofmance increase in IPC. It’s always hard to tell how correct that number is, as Intel in the past simply increase clock frequencies and called that an IPC increase. That, opposed to expensive architecture changes in caches and so on. 
  

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A die-shot of the 18-core Skylake-X series processor

However Intel did change its caches, the L2 cache for example has been increased from 256 kB towards 1 MB per core, which really is significant.  However, relative to that the L3 cache was 2.5 MB and now is 1.375 MB per core, which thus is smaller compared to Broadwell-E.  

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In the above CPU-Z screenshot you can see the chaches on the 7800 (six-core) part. Intel thus tweaked and balanced out the L2 and L3 caches. With the new processors you will also see two Turbo modes dubbed 2.0 and 3.0. We’ll keep it simple, but basically with Turbo mode 3.0 less threads will clock higher. E.g. for a low threaded application a processor could boost with 2 cores to say 4.5 GHz. Whereas Turbo mode 2.0 kick in, it would do say 4 threads at 4.2 GHz. 

A New Processor New Socket

As always, Intel likes to change its socket as often as possible, as hey it’s good to sell more motherboard chipsets. The new Skylake-X processor series will bring Socket 2066 towards the new X299 chipset platform. Intel is to release Skylake-X and Kaby Lake-X at the same time. The difference is simple, Skylake-X can offer 18, 16, 14, 12, 10, 8 and 6 core processors (+ threads). The other (Kaby lake-X) remains to be a quad-core part. So Kaby Lake-X processors will physically fit onto the X299, it however ending up being just a dual-channel memory part. 


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Core i7 7740K

Core i7 7700K

Core i5 7640K

Core i5 7600K

Architecture

Kaby Lake-X

Kaby Lake

Kaby Lake-X

Kaby Lake

CPU cores

4

4

4

4

Threads

8

8

4

4

Base clockspeed

4.2GHz

4.2GHz

4GHz

3.8GHz

Turbo

4.5GHz

4.5GHz

>4GHz

4.2GHz

Cache

8MB L3

8MB L3

6MB L3

6MB L3

Integrated graphics

No

Yes

No

Yes

TDP

112W

91W

112W

91W

Socket

LGA 2066

LGA 1151

LGA 2066

LGA 1151

Chipset

X299

Z270

X299

Z270

Memory support

Dual/Quad channel DDR4

Dual channel DDR4

Dual/Quad channel DDR4

Dual channel DDR4


A  new socket, 2066-socket, and yes that means that once again you have to purchase a new motherboard. This chipset will be called X299, it will offer dual-channel memory for Kaby-Lake X processors, and for the Skylake X processors you get quad-channel support (up-to 2667 MHz). And yes, that means from the four to eighteen-core procs, they all will fit the (expensive) X299 motherboards. There are some changes that you will need to be aware of. First off the DMI interface (the IO interconnect in-between the processor and chipset) is getting  more bandwidth, roughly 4 GB/s. That means you’ll have more PCIe lanes available for other connections in the IO like SATA, M2, USB and so on-wards.


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This is needed as Intel still did not embed USB 3.1 or Thunderbolt 3 inside their processors and thus the motherboard partners rely on external 3rd party chips (and this connection) for such implementations. Kaby Lake-X procs will support dual channel DDR4 and only 16 PCIe 3.0 Lanes, this will be 44 PCIe 3.0 Lanes for the high-end Skylake-X models, not including the 6 and 8-core parts which will get 28 PCIe lanes. The new platform also offers support for Intel Optane. means that once again you have to purchase a new (X299) motherboard.

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