Wel­come to Is­sue 168

SUP­PLIER www.over­clock­ers.co.uk


When In­tel’s Broad­well-E CPUs were re­leased a year ago, they didn’t of­fer any­thing par­tic­u­larly new, aside from the 10-core Core i7-6950X, along with its ridicu­lously ex­pen­sive price that broke the £1,500 bar­rier. Charg­ing that much money for a 10-core desk­top CPU isn’t wise now though. This year, March saw the in­tro­duc­tion of AMD’s Ryzen CPUs, which were not only just as quick clock-for-clock as their In­tel coun­ter­parts in many tests, but also of­fered more cores for the same or less money. Now it’s In­tel’s turn to hit back, with its brand-new Skylake-X range of chips, start­ing with the sub-£1,000, 10-core Core i9-7900X.

That 50 per cent drop in price could be due to sev­eral rea­sons. There’s com­pe­ti­tion from AMD, of course, with its new high-end desk­top (HEDT) plat­form and Thread­rip­per CPUs due to launch later this sum­mer. How­ever, there’s also a more ef­fi­cient 14nm man­u­fac­tur­ing process in play now, and the Core i9-7900X and Core i7-6950X are also quite dif­fer­ent un­der the hood, much more so than the main­stream ver­sions of Broad­well and Skylake.

There’s an­other rea­son, though, which is the fact that this 10-core CPU, un­like its pre­de­ces­sor, is a long way from be­ing the flag­ship of In­tel’s new HEDT plat­form. In­tel has branched out above and below the usual three or four CPUs we nor­mally see at the high end. The real rea­son you’d splash out on In­tel’s HEDT plat­form is clearly to get more cores, and maybe ex­tra PCI-E lanes too – the lat­ter are even more use­ful these days with PCI-E based stor­age be­ing more pop­u­lar.

For any­one who wants the full num­ber of PCI-E lanes, which now sits at 44 – a rise of four over the X99 plat­form’s max­i­mum – you now need to stump up a grand to buy the Core i9-7900X. Not even the 8-core Core i7-7820X has the full num­ber of PCI-E lanes.

Clearly, then, Core i9 is the new nam­ing scheme for CPUs with the max­i­mum PCI-E lanes, but amaz­ingly, the 7900X is the cheap­est of the five CPUs in the range. In­tel will also be re­leas­ing 12, 14, 16 and 18-core CPUs for the new X299 plat­form – the 12-core CPU will ar­rive in Au­gust and the rest in Oc­to­ber, with the new flag­ship be­ing the 36-thread Core i9-7980XE, which is set to cost $2,000 US, with no UK pric­ing an­nounced yet.

The Core i9-7900X sports less L3 cache than the Core i7-6950X as well, but more L2 cache, which could make it more ef­fi­cient in a range of tasks. Both CPUs have the same 140W TDP, but the new chip sports sig­nif­i­cantly higher clock speeds across the board. It has a 300MHz higher base fre­quency and all its cores can boost to a hefty 4GHz, which is 500MHz higher than the older CPU’s turbo fre­quency. There’s also a 500MHz ad­van­tage for the chip’s 2-core Turbo Boost Max Tech­nol­ogy, mean­ing that two of this CPU’s cores can boost to 4.5GHz, com­pared to 4GHz for the Core i7-6950X.

There’s a more ef­fi­cient 14nm man­u­fac­tur­ing process in play


As you’d ex­pect, there wasn’t much of a dif­fer­ence be­tween the Core i7-6950X and new Core i9-7900X in our Gimp im­age edit­ing test, which mainly re­lies on sin­glethreaded per­for­mance.

How­ever, when all ten cores (and 20 threads with Hyper­Thread­ing) kicked in, the Core i9-7900X pro­duced some fan­tas­tic scores. It was more than 100,000 points faster than the Core i7-6950X in our heav­ily multi-threaded Hand­brake video en­cod­ing bench­mark, with the higher all­core turbo fre­quency clear­ing hav­ing a big im­pact, as well as the re­struc­tured cache.

The older CPU was a lit­tle faster in our multi-tasking bench­mark, but that did lit­tle to dent the Core i9-7900X’s huge lead, with an over­all sys­tem score of 230,352 com­pared to 205,205. Mean­while, the 8-core Ryzen 7 1800X man­aged a re­spectable 174,195, which wasn’t far be­hind, de­spite cost­ing half the price – a 10-core Ryzen CPU will likely be com­pet­i­tive here. In Ashes of the Sin­gu­lar­ity: Es­ca­la­tion, the older CPU had a lead, with a min­i­mum frame rate of 45fps com­pared to 44fps, but in ev­ery other test, the Skylake-X CPU was ut­terly dom­i­nant. It was 12 per cent quicker in Ter­ra­gen 4 and recorded a much higher score in Cinebench too.

When all ten cores kicked in, it pro­duced some fan­tas­tic scores

We then wanted to see how far we could overclock this 10-core mon­ster, and we man­aged to hit 4.6GHz with a vcore of 1.24V, which is 200MHz higher than we man­aged with the Core i7-6950X, and with sig­nif­i­cantly less volt­age too. How­ever, the fact that In­tel has used ther­mal paste and not solder be­tween the CPU and heat­spreader was very ev­i­dent, as the new CPU got hot­ter much more quickly than the Broad­well-E CPU, even at lower volt­ages. Still, tem­per­a­tures were eas­ily tame­able at 4.6GHz across all ten cores with an all-in-one liq­uid cooler, mak­ing for an awe­somely pow­er­ful CPU.

This overclock saw the sys­tem score rise over 12 per cent to 258,546, which was over 5 per­cent faster than the over­clocked Core i7-6950X. The Cinebench score rose by nearly 300 points too, giv­ing it a near 200-point lead over the older CPU at 2,476 com­pared to 2,215. How­ever, Ashes of the Sin­gu­lar­ity re­mained stub­bornly low – once you get to this level of CPU power, it looks like you won’t get any faster per­for­mance. Un­der heavy loads, the new CPU was a good deal more power-hun­gry, though, draw­ing 270W from the wall com­pared to 196W for the Core i7-6950X, although the two chips’ power con­sump­tion was sim­i­lar once over­clocked, de­spite the new CPU en­joy­ing a 200MHz clock speed ad­van­tage.


There’s no doubt that, de­spite some toasty tem­per­a­tures and a higher power draw, the Core i9-7900X is a much faster CPU than the Core i7-6950X in nearly ev­ery area – sig­nif­i­cantly so in some cases. The all-core boost to 4GHz at stock speed is mas­sively pow­er­ful, although in value terms, AMD’s Ryzen chips of­fer su­pe­rior bang per buck, cost­ing half as much money for just a 2-core deficit. That said, thanks to the re­designed cache and higher fre­quen­cies, In­tel’s Skylake-X ar­chi­tec­ture looks like it could be faster than Ryzen, aside from just core counts.

Still, the new CPU isn’t twice as fast as the Ryzen chip, de­spite cost­ing twice as much money, and if AMD gets its pric­ing right, we can ex­pect a tan­ta­lis­ing bat­tle at the high end be­tween Thread­rip­per and Core i9. In­tel’s Skylake-X CPUs also ap­pear to be able to get to higher over­clocked fre­quen­cies than their pre­de­ces­sors, and a solid 4.6GHz fre­quency will mean you’re only a lit­tle be­hind what a Core i7-7700K would man­age. In short, the Core i9-7900X is a mon­ster CPU that’s over­clock­able, and the po­ten­tial for a 4.6GHz 10-core CPU is likely to make any en­thu­si­ast drool. That said, if you have the money, and you want as much multi-threaded CPU power as pos­si­ble, we rec­om­mend hold­ing out a few months to see what the other Core i9 CPUs can of­fer, as well as AMD’s Thread­rip­per chips.

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