Skylake-X And Kaby Lake-X Thread

[SteelCrysis]

http://techreport.com/review/32111/intel...part-one/8
http://techreport.com/review/32111/intel...part-one/9

At idle, the X299 platform paired with the Core i9-7900X sips only a bit more power than the Core i7-7700K. Under load, however, the 7900X system consumes the most power at peak load by a wide margin. Of course, peak power draw only tells part of the efficiency story.

To really get a sense of how efficient the Core i9-7900X is, we need to take the task energy consumed over the course of our Blender benchmark into account. Not only does the Core i9-7900X cut 94 seconds off the Ryzen 7 1800X's bmw27 render time, it does it while expending only just a bit more power to do so. That's impressive performance per watt.
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Our value scatter tells the entire story of the Core i9-7900X: if your workload scales to many threads, this chip is generally the one to run it on. The server version of Skylake delivers an unusually large performance boost for a modern Intel CPU revision in many tasks. Core for core and thread for thread, the already-beastly Core i7-6950X can sometimes lag the 7900X in the range of 10% to 20%. All that oomph comes for a jaw-dropping $724 less than the 6950X's initial suggested price, too. Competition is a wonderful thing.

In a milestone for Intel's high-end desktop platform, the Core i9-7900X mostly ends the tradeoff between single-threaded swiftness and multi-threaded grunt typical of some older Intel high-end desktop chips. For lightly-threaded workloads, the i9-7900X's improved Turbo Boost Max 3.0 behavior lets it trail our single-thread-favorite Core i7-7700K by only a few percentage points at most. In typical desktop use, then, the i9-7900X and its TBM 3.0-enabled brethren should feel about as snappy as their mainstream desktop cousins. I need to get the i9-7900X paired up with a GeForce GTX 1080 Ti soon to see whether that single-threaded performance translates to similar gameplay smoothness.
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We've always been loath to recommend the top-end CPU in Intel's high-end desktop family (and yes, that is this chip for the moment). Despite the Ryzen-inspired price reshuffling that's coming with Core X, the i9-7900X still isn't a great value. The star of the Core X lineup may actually be the Core i7-7820X, whose eight cores and 16 threads have clocks similar to those of the i9-7900X. You may lose a couple of cores in the bargain, but even so, the i7-7820X should perform better than a Ryzen 7 1800X for not that much more money. We hope to play with one of these more attainable Skylake-X CPUs soon.

Of course, the performance of the Core i9-7900X is beyond question: it's the fastest single-socket CPU we've ever tested. The X299 platform may need a little polish yet to let Core X chips really shine, but the performance bar the i9-7900X is already setting promises an exciting standoff this summer as AMD prepares its Ryzen Threadripper CPUs for launch. If you need as many cores and threads as possible from your desktop, times have never been more exciting. Stay tuned as we see whether the i9-7900X has got game.

http://www.tomshardware.com/reviews/inte...92-11.html
http://www.tomshardware.com/reviews/inte...92-12.html

As mentioned, we had to use Alphacool's Eiszeit Chiller 2000 to achieve usable overclocking results. More conventional thermal solutions just wouldn't cut it. All-in-ones like Corsair's H100i and Enermax's LiqTech 240 hit their limits at stock frequencies under Prime95. The custom loop threw in the towel at 4.6 GHz.

Why can't those liquid coolers keep up with a CPU like the -7900X? Back in the day, a normal all-in-one was good enough to keep the Core i7-5960X running cool, even overclocked to 4.8 GHz. We measured power consumption numbers of up to 250W back then. So, why did we have to force a constant 20°C in the loop to even start experimenting?

The reason that Skylake-X is so much harder to cool traces back to the thermal paste Intel chose to use instead of solder between the processor die and heat spreader. Although paste is cheaper, it's also less than ideal for cooling performance.

Intel’s digital temperature sensors report reliable results from 35 to 40°C and up, prompting us to only include values above that range in our analysis. The difference between the water cooling block's temperature, which is held at a constant 20°C, and the CPU temperature reported by Intel's sensors shows just how bad of a choice thermal paste really was.

We measured the CPU heat spreader’s temperature the same way we did when AMD launched Ryzen 7 1800X, by using a thin copper plate. The resulting curve shows very clearly that waste heat can't be dissipated quickly enough. A solution good enough for a thermal lightweight like Intel's Core i7-7700K just doesn’t work for Core i9-7900X.

This curve represents the temperature delta, which is to say the thermal difference between Core i9-7900X’s cores and the top of its heat spreader. The outcome is shocking:

In the end, the delta between the cores and top of the heat spreader reaches 71°C, and that's using one of the best cooling setups money can buy. Naturally, lesser thermal solutions start running into trouble at stock frequencies when you run a stress test.

To illustrate our point, we plotted the temperature for all of the Core i9-7900X’s cores at stock settings running Prime95 or LuxRender. A good custom water-cooling loop does fairly well, which shouldn't come as a surprise. However, no other thermal solution will be able to keep up. Even the motherboard manufacturers we spoke to agree, telling us about their all-in-one liquid coolers running out of headroom as soon as they ran Prime95 without limiting AVX.

A Tcore of up to 65°C and a heat spreader temperature of approximately 24°C make for a difference of more than 40°C. That's at 230W. Once the 300W line is crossed, even the Alphacool Eiszeit Chiller 2000 taps out. This isn’t even difficult to do: with a Core i9-7900X running at 4.6 or 4.7 GHz, using the voltages needed to get there, even simple rendering applications trigger those levels. The highest power consumption numbers we saw were just north of 300W, which had the CPU hitting its 100°C thermal limit consistently. An emergency shutdown followed soon after.

Next, we measured power consumption under a constant load using different coolers. For a temperature increase of approximately 40°C, power consumption increases by five percent. This isn’t just an acceptable result, but a really good one. The values above 100°C are not as reliable due to throttling. Consequently, we made an exception and used a low-pass filter that smoothed out the brief decreases.

Everything could have been great, if it wasn't for the thermal paste between Intel's die and heat spreader. Admittedly, most workstation or semi-pro users won't overclock, cutting down on the number of customers affected by this problem. But we all know that affluent enthusiasts attracted to Skylake-X's balance between high frequencies and core counts will have to face a significant cooling challenge. Your choices come down to high-end all-in-one packages or a custom water-cooling loop. Air cooling is completely out of the question if you expect the -7900X to run comfortably under full load.

Intel’s market dominance burdens the company with certain expectations when it launches new hardware. Naturally, we expect more performance. And although we're quick to deride incremental updates, forward progress is what we want to see. At no point is a step backward alright in our books, and we saw a handful of those in today's tests.
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As it stands, aggressive Turbo Boost frequencies and a re-balanced cache hierarchy go a long way to improving on Broadwell-E's minor weaknesses. When the Core i9-7900X does well, it really shines. Often, the chip beats every competitor we throw up against it, including Core i7-6950X. In other workloads, latency imposed by its mesh topology causes Core i9 to stumble. That isn’t to say performance falls off completely. But we do see anomalies unfitting of a $1000 CPU. If you're strictly a gamer, Core i9-7900X won't make you want to buy a new CPU, motherboard, and memory kit.

Enthusiasts also want to see robust overclocking capabilities, and Skylake-X does offer a higher frequency ceiling than Core i7-6950X. You're going to cope with a lot of heat in the process, though. Given Intel’s insistence on using thermal paste between its die and heat spreader for longer-term reliability, the processor can’t dissipate heat as effectively, so thermal performance becomes a limiting factor. Plan on investing in a beefy open loop if you want to push the Core i9-7900X much further than its stock frequencies.

Core i9-7900X performs well in our productivity, workstation, and HPC tests. The mesh-imposed disparities aren't as pronounced in those benchmarks. But we also have re-run Ryzen 7 1800X benchmarks to think about. Pressure to size up has pushed AMD's flagship down to $460, less than half of what a Core i9-7900X would cost. While Intel may capture the top 1% of high-end enthusiasts with Skylake-X, everyone else has to consider whether Ryzen may be the smarter buy.

Moreover, AMD's upcoming Threadripper CPU has to have Intel worried. How do we know? The X299 motherboards we used needed firmware updates to address very serious performance issues right up until launch. Intel didn't seem nearly as ready for Skylake-X's introduction as we'd expect. A number of Core i9s with even more cores won't be ready until later this year. However, it looks like Intel couldn't get the four-, six-, eight-, and 10-core models out fast enough. They'll ship later this month.

Unfortunately, this story won't be ready to wrap up until we have Threadripper to compare against. Given Core i9-7900X’s high price and performance caveats, enthusiasts should probably hold off on a purchase until we know more about the competition, even if Skylake-X looks like a bigger step forward than Intel's past HEDT designs.