Review: Intel Core i7-5775C

Introduction and features

Intel’s first 5th generation Core desktop CPU, the Intel Core i7 5775C, is finally in our test benches. So, hey there, Mr. Broadwell, what took you so long?

If you were to talk to anyone at Intel, they’d tell you the 14nm Broadwell CPU architecture was released back in 2014. After all, there is no delaying the classic Intel ‘tick, tock’ CPU design cadence.

And yet, here we are in the summer of 2015 and we’ve only just got our hands on the first proper Broadwell processors. By ‘proper’ I’m talking about full-fat, quad-core desktop processors, with capable clock speeds and the overclocking potential we know and love.

Technically though Broadwell was released in 2014. Well, some of it. The Core M, a dual-core, HyperThreaded mobile chip, was officially released just before Christmas with a few more low-powered Broadwell variants appearing in laptops the following spring.

So is this a case of Intel de-prioritising desktop processors and is that more worryingly an indication of the limited range we can expect from the imminent Skylake family of desktop chips?

In a word, no.

Power savings

Broadwell has always been about power saving, so those mobile parts were always going to be the priority. And, as Broadwell has slipped further and further back along the production schedule, barrelling head-long into the next-gen CPU launch of Skylake, there really isn’t a need to produce a full range of different socketed processors.

To be honest, I’d even argue there’s almost no reason to have even bothered releasing a socketed Broadwell CPU at all. Skylake is only a matter of weeks away now and that will bring us bona fide high-performance, low-power chips – that’s not something Broadwell in this guise can claim.

Though as a teaser for what Skylake could produce it’s definitely worth a look.

Architecture

So what actually is Broadwell? It’s the tick to the Haswell architecture’s tock.

Decoding Intel parlance that makes it a 14nm production process die shrink on what is still essentially Haswell CPU technology. And with the shrinking of the smallest transistors down from 22nm to 14nm that gives the Broadwell chips some serious power efficiency.

That’s why they’re first and foremost of interest to the mobile crew.

But they still retain some interest on the desktop for the fact that, along with the new 14nm lithography, you also get the very best in processor graphics in both of the new Broadwell desktop CPUs.

This is the first time the Iris Pro level of graphics has appeared in socketed form, and both this Intel Core i7 5775C and the Intel Core i5 5675C are happily rocking the much-improved graphics core. Compared with the HD Graphics 4600 parts in the latest Haswell Devil’s Canyon chips, the Iris Pro 6200 boasts more than twice the execution units (EUs), the Intel spiritual equivalent of Nvidia and AMD’s GPU ‘cores’.

Elsewhere you’re looking at classic Core i7 stats – four cores with eight threads – but because this a ‘C’ class of chip rather than the classic top-end ‘K’ series you’re only getting a clock speed of 3.3GHz with a max turbo of 3.7GHz. Though both these ‘C’ class chips are still retaining unlocked multipliers, to aid overclocking.

The top last-gen Haswell chip, the Core i7 4790K, on the other hand boasts a peak turbo of 4.4GHz. It also has a higher level of cache, but an 88W TDP as opposed to the 65W TDP of these latest Broadwells.

Performance

The actual raw performance is the meat of the matter, though, isn’t it? The Core i7 5775C is technologically the top processor in Intel’s standard desktop line-up. Well, for the next few weeks until Skylake drops anyways…

But what does this £300 (around $470, or AU$630) processor offer that makes it a relevant upgrade to the cheaper Devil’s Canyon Core i7?

Cue steady intake of breath and teeth-sucking…

That’s a tricky question because on the face of it there seems to be no reason to upgrade from your current Haswell i7 – and I’d probably say the same for most existing i5 chips too. The Core i7 5775C is a good chunk of change more expensive than the i7 4790K and in terms of straight clock speed, and thus gaming performance, it’s a bit of a bust.

The clear air between the two regarding clock speed is the real kicker right there. The 5775C theoretically maxes out its Turbo clock at 3.7GHz, but in our testing we never saw it go above 3.6GHz. That was with both the Asus or ASRock Z97 boards we tested with.

When the 4790K is hitting 4.4GHz at stock clock speeds that gives it a pretty hefty performance lead when it comes to standard gaming performance. It’s the same across our suite of benchmarks – both X264 and Cinebench give a landslide victory to the last-gen CPU.

The bright spot though is in the memory bandwidth figures. The Broadwell chip shows significant improvements in memory performance, topping anything we’ve seen outside the server-bothering antics of the Ivy Bridge E processors.

And what of overclocking? That die-shrink ought to deliver improved overclocking prowess, but whether it’s the limitations of the motherboard we were using, the limits of our CPU review sample or merely immature board/chip drivers, we couldn’t quite hit the standard 1GHz overclock Intel CPUs often offer.

Boosting it from a 3.3GHz base up to 4.2GHz is no mean feat however and does improve performance, but nowhere near enough to worry the existing top Haswell chip in straight CPU performance terms.

Power sipping

But this isn’t where Broadwell is meant to compete. Despite the crazy-high price tag this isn’t a high-end CPU, this is a low-power Core i7 with high-end graphics and some limited overclocking performance. That in itself is a rarity.

And if you’re desperately after a low-powered processor but still one with a bit of oomph behind it then this could be your chip. At stock speeds the peak power we were seeing during Cinebench testing runs was just 104W, with the CPU only a shade over 50 degrees.

Now, given the low clock speed that’s possibly to be expected. But even when overclocked up to 4.2GHz the CPU was still well under 60 degrees and only drew another 50W at maximum.

That’s some seriously impressive power and temperature efficiencies – you can see why it’s a mobile part in the main. It’s a shame our testing setup couldn’t push the overclocking any further because there simply wasn’t any thermal throttling within eye-shot of the Broadwell chip.

Unfortunately some issues with our sample and our standard Asus RoG Maximus VII Hero board meant it wouldn’t overclock, so we had to switch to the less-able ASRock Z97 Extreme4. That’s still a quality board, but not quite on the same level as the RoG in the overclocking stakes. A little extra voltage gained us an OS boot at 4.4GHz, but nothing stable.

Processor graphics

We haven’t spoken about the graphics performance yet though, but that is a massive improvement over the CPU graphics of the Haswell regime. Having more than twice the EUs of the HD Graphics 4600 – 48 plays 20 – the Iris Pro 6200 delivers a huge performance boost over the top socketed Haswell chips.

The difference at top 1080p settings means gaming performance actually goes from practically slideshow levels to genuinely playable. Adjust your visual expectations a touch and you’ll get decent 1080p gaming performance out of the i7 5775C.

Importantly though the Core i5 5675C has the same graphics core for a lot less – making that a far more tempting chip if you’re after quality CPU graphics performance without the price premium attached to an i7.

Benchmarks

CPU processing performance

Cinebench R15 – Index score: higher is better

• Intel Core i7 5775C: 763
• Intel Core i7 4790: 880
• Intel Core i5 4690K: 586

X264 v4.0 – Average FPS: higher is better

• Intel Core i7 5775C: 45
• Intel Core i7 4790K: 53
• Intel Core i5 4690K: 40

Memory performance

SiSoft Sandra – GB/s: higher is better

• Intel Core i7 5775C: 20.14
• Intel Core i7 4790K: 17.73
• Intel Core i5 4690K: 17.72

1080p gaming performance (w/GTX 780 Ti)

Metro: Last Light – (min) Avg FPS: higher is better

• Intel Core i7 5775C: (20) 44
• Intel Core i7 4790K: (11) 52
• Intel Core i5 4690K: (10) 52

Battlefield 4 – (min) Avg FPS: higher is better

• Intel Core i7 5775C: (58) 77
• Intel Core i7 4790K: (59) 94
• Intel Core i5 4690K: (53) 86

Power and overclocking

Peak platform power draw – Watts: lower is better

• Intel Core i7 5775C: 104
• Intel Core i7 4790K: 195
• Intel Core i5 4690K: 122

Maximum overclock – GHz: higher is better

• Intel Core i7 5775C: 4.2
• Intel Core i7 4790K: 4.7
• Intel Core i5 4690K: 4.7

Processor graphics performance

Cinebench R15 OpenGL – Avg FPS: higher is better

• Intel Iris Pro 6200: 54.35
• Intel HD Graphics 4600: 33.15

Bioshock Infinite – (min) Avg FPS: higher is better

• Intel Iris Pro 6200: (6) 20
• Intel HD Graphics 4600: (2) 11

Grid 2 – (min) Avg FPS: higher is better

• Intel Iris Pro 6200: (24) 30
• Intel HD Graphics 4600: (15) 19

Verdict

As a preview of what we can expect from the top end of the next-gen Skylake processor family this 14nm die shrink of the existing Haswell architecture is very welcome, darned impressive even.

The thought of encouraging anyone to spend £300 (around $470, or AU$630) on buying one though is beyond the pale.

Even with the excellent Iris Pro graphics finally hitting socketed CPUs – and down to the i5 level too – we struggle to see who these two processors are aimed at and, more importantly, who would actually consider picking one up.

The argument from Intel is that it represents a technological upgrade from Haswell that doesn’t require an entire platform change. Update your motherboard’s BIOS, drop in one of the new chips and, hey presto, you now have new Broadwell architecture in your rig.

Except that if you’ve upgraded from pretty much any Core i7 Haswell you’re almost certain to get a performance drop on anything you do with your PC. Gaming performance is way down – in fact if you upgraded from a Core i5 you’d be getting a performance hit in those terms.

But that 14nm die shrink has yielded a huge drop in the power requirements and in the heat of the relative chips. Right now that doesn’t translate into big overclocking numbers without some serious BIOS surgery and voltage tweaking, but as an indication of where we’re going with the soon-to-be-here Skylake, it’s very exciting.

We liked

The new Iris Pro 6200 graphics core is very welcome. With the i5 Broadwell you can create a tiny machine which doesn’t need a discrete GPU to hit playable, mid-range, 1080p gaming performance without it costing a fortune.

The high price of this i7 though makes that less of a selling point, but the fact remains the graphical speed hike over Haswell is huge. Let’s hope Skylake carries on this trend of high-end GPUs in more mainstream CPUs, but I wouldn’t hold my breath.

The most impressive thing about the Broadwell chip, however, is the low power and temperature performance. This eight-threaded CPU is barely drawing the same power as the last-gen quad-thread parts.

We disliked

That low clock speed means that this is no high-end part. The fact you get the low power and low temperatures when hitting 4.2GHz might indicate Intel could have clocked this chip higher out-of-the-box. Though that being our overclocking limit might also indicate it couldn’t really push things much higher and still remain 100% stable.

We also find the high price a real sticking point. The i7 5775C is priced well above the Devil’s Canyon i7 4790K, which is a bona fide high-end desktop CPU. And yet it can’t compete in anything outside of power and temperature efficiency.

We also don’t like the fact this chip is so late as to be almost entirely irrelevant. With the imminent release of Skylake we struggle to see why Intel even released a socketed desktop version at all.

Final verdict

This is a chip that might have looked impressive last year and might still have made a case as an upgrade today if it had a higher clock speed and a more reasonable price. But that high price tag, and the fact Skylake is but a matter of weeks away, means there’s little reason for anyone to consider this a worthwhile purchase.

Yes, it has an impressive GPU component and maybe the Core i5 version has a place as an upgrade from a low-end Core i3-based machine without a discrete graphics card. But this expensive, low-performing processor is going to win few friends with anyone wanting Broadwell to offer tangible performance boosts over their Haswell CPUs.