Over the last few Intel processor reviews, I have been getting a feeling that even though there are always new overclocker-oriented features, the CPUs themselves have been doing their best to thwart higher clock speeds. Broadwell-E continues down this path by offering up a plethora of options that will surely make enthusiasts drool and newcomers’ eyes glaze over but actually getting these processors to move past the 4.5GHz mark proved to be a bridge too far.
Broadwell-E offers up a bunch of options for wringing the most out of its processors, many of which still have that new car smell. All of these CPUs will be completely unlocked but Intel has now added core-by-core overclocking. That isn’t anything new but when used in conjunction with the “Best Core” indicator I mentioned earlier in the review, you will be able to directly target your OCing efforts towards the cores which are most likely to return optimal results. For example if (in my case) cores 9, 4, 8 and 3 were indicative as being able to reach higher Turbo frequencies than the others, I’d push them upwards first while also insuring Intel’s software prioritizes their use in key applications like games.
The next up is AVX Ratio Offset and after reading through dozens of pages of information, ASUS’ description is likely the most apt I have come across:
It is a given that each new processor architecture from Intel features enhancements for workload-specific performance. That quest continues with Broadwell-E, which features a mechanism called AVX Offset. The parent of this mechanism was first seen on server platforms a couple of years ago, although it was not available for user adjustment – server CPUs are usually locked, so no surprises there. The mechanism was introduced because AVX workloads consume a lot more current than ones that use the default instruction set.
The AVX Offset mechanism is designed to work in conjunction with Auto mode for voltage; when an AVX workload is detected, the processor reduces its frequency, which is followed by a reduction in core voltage via the on-die power control unit (PCU). These low-latency, on-the-fly changes, keep the CPU within Intel’s defined TDP limit. Ultimately, this allows higher processor frequencies for non-AVX workloads, which has obvious performance benefits.
Unlike on server platforms, the AVX Offset register is open for adjustment on Broadwell-E processors, which makes it possible for us to define the AVX workload ratio. The adjustment option is certainly welcome. However, the mandatory condition is that we have to leave processor voltage in Auto mode to reduce operating temperatures under AVX workloads, and this has implications for overclocking – more on this later.
On to the Results
So now with that out of the way, let’s talk about the trials and tribulations when it comes to overclocking the i7-6950X and i7-6900K. After spending about three hours with each processor (admittedly not much but I’ve only had these things in-hand for a few days now) it’s quite evident that they run relatively cool even when overclocked. However, I decided to limit my voltage options to points below 1.36V which is what I feel is safe for long term 24/7 use so it could very well be that folks who want to push things even further could do exactly that. Also note this was all done on ASUS very, very affordable X99 A-II motherboard.
Another thing to take into account is that “24/7” number. I don’t aim for suicide runs or to post results here that aren’t completely 3D stable for at least 2 hours of continual gaming. Maybe that limited achievable clock speeds as well but after talking to various motherboard vendors, their labs aren’t having all that much success breaking past the 4.5GHz barrier unless higher amounts of voltage are used. Nonetheless I was hoping for a bit more from these chips since they literally ran into a roadblock just north of 4.4GHz.
Starting off with the i7-6950X and it was able to hit a constant frequency of 4.43GHz on all ten cores. Unfortunately, pushing even a bit above that to 4.45GHz via a simple ratio increase or offset hard locked the system the moment a multi threaded application was launched. Even trying to get things going with the 45x multiplier proved to be a bridge too far.
When you consider this chip typically runs at up to 3.5GHz, a nearly 1GHz overclock isn’t bad at all though and the performance numbers were pretty impressive as well.
I was hoping for big things from the i7-6900X but it literally hit the exact same brick wall as its sibling. The 45x multiplier resulted in the system smashing face first into a hard lock the moment benchmarking began (though booting into Windows was never a problem). The end result was 4.46GHz which once again isn’t necessarily a bad result but I’m sure some expected better.
I do however have to emphasize that I’ve had very little time overclocking Broadwell-E before this review goes live and things will likely (hopefully!) change for the better once I get acquainted a bit better with the platform’s limitations and ultimate capabilities.
Intel’s i7-6950X and i7-6900K Broadwell-E processors are ridiculously fast, very efficient and are priced to such stratospheric levels that they’re going to be held up as perfect examples of unobtainium by the vast majority of gamers, power users and enthusiasts. Expensive though they may be, there’s obviously a market out there which is ready and willing to embrace these things. There are also people who just want to experience what cutting edge technology feels like and for them, Broadwell-E delivers.
I want to break this conclusion up into two sections before going any further; one for the i7-6950X and the other for Intel’s more affordable alternative, the still-costly i7-6900K. Unfortunately I wasn’t able to source the 6800K-series in time for this review but expect full benchmarks on those very soon.
We’ve all been talking about multi-tasking for years now but the i7-6950X may be the first processor that takes the term “mega tasking” to heart and then shows it who's daddy. If this thing was a maid, it would be cleaning your kitchen while doing the laundry, and washing the car….all while building you a new deck. Those ten cores and twenty effective threads bring new meaning to the words processing powerhouse. However, it takes a very specific subset of users to effectively utilize this kind of horsepower; they’re the ones who want to game while running high level processing tasks in the background without missing a beat.
As a matter of fact, due to its price, I wouldn’t even begin to consider the 6950X as a pure gaming-only CPU since its performance at 1080P and beyond is very good but simply too close to much less expensive alternatives. Yes DX12 may change this in some way -perhaps in situations where the 20 threads can obfuscate a given architecture’s lackluster asynchronous task management- but it would be quick sales suicide for a game designer to require more than a quartet of cores for a game to run optimally. Think about that before you take this particular plunge. Also remember that for the price difference between it and the i7-6900K, you could buy a GTX 1080 and still have a few bucks left over to treat your girl to a nice “I’m sorry I spent so much on a gaming rig” dinner.
Where the 6950X truly shines is within highly threaded processing environments. Scene rendering, video conversion, application streaming and other workloads are its natural habitat. The performance in CineBench brought it all home for me. With other processors I could press the Run button, head upstairs to grab a snack, throw in a load of laundry and make it down to the office before the benchmark completed. This time I was barely able to make it out of my chair before the application spat out an obscenely high result. I’m sure my expression of open-mouthed wonderment right then would have made for a perfect GIF image.
The i7-6900X may take a Tonto-like sidekick position relative to the i7-6950X’s Lone Ranger but it still packs an almighty performance punch. Yes it is still be priced at near-insanity levels but it still boasts some noteworthy improvements over the also-expensive Haswell-E flagship. If anything Intel’s Turbo Boost Max 3.0 makes its presence known here at least from a comparative standpoint against a very similar CPU which doesn’t include support for this new feature. Though the technology could obviously “accelerate” a limited number of applications and synthetic benchmarks it nonetheless provided an eye opening peek into what’s possible with adjustable core affinity.
I feel the i7-6900K strikes a very good balance for those who are looking for extreme output without ponying up the cash for an i7-6950X. While it may not be a purebred mega tasker and I can’t imagine a situation where a gamer would require more than eight threads, it grants enough flexibility for usage in a multitude of diverse situations. It’s that Swiss Army Knife approach which could make the $1090 entry cost a bit more palatable for some potential buyers...or not.
That price will be something brought up again and again. We're obviously seeing the results of Intel operating without any competition in this price range and its becoming a scary thing. Even that "more affordable" i7-6900K is still almost $100 more than a processor launched almost two years ago and it doesn't offer substantially better performance. Meanwhile the i7-6950X dares enthusiasts to take the plunge and almost makes a mockery of their willingness to do exactly that. Intel knows they can charge what they want for these things and they're doing exactly that.
Perhaps the most impressive thing about these two processors is their relative efficiency. Yeah I know, lowered power consumption is the flavor of the month but don’t let that lessen Intel’s achievement in any way. We now have high speed eight and ten core processors which consume about as much or less electricity than their predecessors while offering –at times- significantly higher performance.
Overclocking will be for the most part disappointing on the i7-6900K and i7-6950X, at least for those who wanted to achieve Haswell-E like speeds on liquid cooling. After polling every one of the major motherboard vendors, 4.5GHz and 4.2GHz on the i7-6900K and i7-6950X respectively seem to be the average plateaus. As evidenced by the overclocking section, those numbers fall very much into my experiences as well. But with that being said there will always be outlier cases that will provide more or even less headroom than my engineering samples. Luckily it looks like a good AIO will be sufficient to achieve a reasonably high 24/7 stable frequency boost, even on the deca core chip.
While Intel’s new offerings represent impressive achievements in their own right, they are tied at the hip to a platform that’s really starting to show its age. Back when X79 was launched, I made the same observation about Ivy Bridge-E but the disparity between X99 and Z170 is an order of magnitude larger. The last two years have experienced an explosion in the storage market and yet Intel have saddled enthusiasts with an almost insultingly under-equipped chipset. The latest drives from the likes of OCZ, Samsung, Crucial, and even Intel themselves veritably gobble up PCI-E 3.0 lanes and yet X99 requires key processor-based lanes be used for those tasks.
On 40-lane CPUs like the ones in this review, the situation is somewhat mitigated but with a pair of GPUs installed, there’s just eight lanes left tertiary I/O needs. With new SSDs, Thunderbolt, USB 3.1 and other interfaces all looking for that same pathway, Broadwell-E users (particularly those with an i7-6800K) could soon find themselves wishing for a mainstream Skylake Z170 board.
Based on price alone Intel’s i7-6950X and i7-6900K certainly aren’t for everyone and their premium versus the previous generation may alienate some potential buyers. However, for those who see value in extreme levels of performance or just want the fastest desktop CPUs currently in existence, these processors represent the best (and only) solutions available. If anything, we all have to appreciate them since they represent a technological tour de force of epic proportions even though pricing has gone way out of wack.
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