Intel Core i7-5775C Review – Intel’s fifth-gen desktop CPU, the Core i7-5775C, is finally in our test benches. So hey there, Mr Broadwell, what took you so long? If you talk to anyone at Intel, they tell you the 14nm architecture was released in 2014. And yet we’ve only just got our hands on the first proper Broadwell processors. By ‘proper’, we’re talking full-fat, quadcore desktop processors, with capable clockspeeds and overclocking potential.
Technically, Broadwell was released in 2014. Well, some of it. The Core M, a dualcore, Hyperthreaded mobile chip, was officially launched before Christmas, with some low-powered variants appearing in laptops in spring. So, is this a case of Intel de-prioritising desktops? And is it a worrying indication of what we can expect from the imminent Skylake family of desktop chips? In a word, no. Broadwell has always been about power saving, so those mobile parts were inevitably going to be the priority. And, as Broadwell has slipped further back along the schedule, barrelling into the next-gen Skylake launch, there really isn’t a need to produce a full range of different-socketed processors.
To be honest, we’d argue there’s almost no reason to have bothered releasing a socketed Broadwell CPU at all. Skylake is weeks away and that will bring us bona fide high-performance, low-power chips. As a teaser for what Skylake could produce, however, Broadwell is worth a look.
So what is Broadwell? It’s the tick to Haswell’s tock. That makes it a 14nm production process die shrink on what’s still essentially Haswell CPU tech. And with the shrinking of transistors to 14nm, Broadwell chips gain serious power efficiency. That’s why they’re first and foremost of interest to the mobile crew.
But they retain some interest on the desktop because you also get the very best in processor graphics. This is the first time the Iris Pro level of graphics has appeared in socketed form, and both this i7-5775C and the i5-5675C are rocking the muchimproved graphics core. Compared with the HD Graphics 4600 parts in the latest Haswell Devil’s Canyon chips, the Iris Pro 6200 has more than twice the execution units (EUs).
Elsewhere, you’re looking at classic Core i7 stats – four cores with eight threads. But, because this a ‘C’ class of chip, you’re only getting a clockspeed of 3.3GHz with a max turbo of 3.7GHz, though both these ‘C’ class chips are retaining unlocked multipliers to aid overclocking.
The top last-gen Haswell chip, the Core i7-4790K, incidentally, 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.
This is the meat of the matter. The i7- 5775C is technologically the top processor in Intel’s standard desktop lineup. For the next few weeks, anyways. But what does this £300 processor offer that makes it a relevant upgrade to the cheaper Devil’s Canyon Core i7? Cue steady intake of breath and teeth-sucking.
On the face of it, there seems to be no reason to upgrade from your current Haswell i7, and probably most existing i5 chips. The i7-5775C is a good chunk more expensive than the i7-4790K, and, in terms of straight clockspeed, and thus gaming performance, it’s a bit of a bust. The clear air regarding clockspeed is the real kicker. The 5775C theoretically maxes its Turbo clock at 3.7GHz, but in our testing, we never beat 3.6GHz. When the 4790K is hitting 4.4GHz at stock clockspeeds, that gives it a pretty hefty performance lead. It’s the same across our suite of benchmarks – X264 and Cinebench gave a landslide victory to the last-gen CPU.
The bright spot is in the memory bandwidth figures. The Broadwell chip shows big improvements, topping anything we’ve seen outside the server-bothering antics of Ivy Bridge-E processors. And what of overclocking? That die-shrink ought to deliver improvements, but whether it’s the limitations of the mobos we were using, the limits of our CPU review sample or merely immature board/chip drivers, we couldn’t hit the standard 1GHz overclock that Intel CPUs often offer. Boosting it from a 3.3GHz base up to 4.2GHz is no mean feat and does improve performance, but nowhere near enough to worry the existing top Haswell chip in straight performance.
But this isn’t where Broadwell is meant to compete. It’s a low-power i7 with highend graphics and limited overclocking. At stock speeds, the peak power we were seeing during Cinebench tests was just 104W, with the CPU only a shade over 50°C. Given the low clockspeed, that’s possibly to be expected. But even when overclocked to 4.2GHz, the CPU was still under 60°C and only drew another 50W at maximum.
That’s some seriously impressive efficiencies. This eight-threaded CPU is barely drawing the same power as last-gen quad-thread parts. It’s a shame our testing setup couldn’t push the overclocking further because there simply wasn’t any thermal throttling within eye-shot.
Unfortunately, some issues with our sample and our standard Asus RoG Maximus VII Ranger board meant it wouldn’t overclock, so we had to switch to the lessable ASRock Z97 Extreme4. That’s still a quality board, but not quite on the same level in the overclocking stakes. A little extra voltage gained us an OS boot at 4.4GHz, but nothing stable.
We haven’t spoken about graphics performance yet. Having more than twice the EUs of the Haswell regime’s HD Graphics 4600 – 48 plays 20 – the Iris Pro 6200 delivers a huge performance boost. Gaming at top 1080p settings goes from practically slideshow levels to genuinely playable. Importantly though, the i5-5675C has the same graphics core for cheaper – making that a far more tempting chip.
Going Iris Pro
As a preview of what we can expect from the next-gen Skylake family, this 14nm die shrink of the existing Haswell architecture is very welcome. Darned impressive even. But the thought of spending £300 on one is beyond the pale. Even with the excellent Iris Pro graphics finally hitting socketed CPUs, we struggle to see who would actually consider picking one up.
The argument from Intel is that it represents a technological upgrade from Haswell that doesn’t require a platform change. Update your mobo’s BIOS, drop in a chip and, hey presto, you now have new Broadwell architecture in your rig. Except that if you’ve upgraded from pretty much any i7 Haswell, you’re almost certain to get a performance drop.
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 Skylake, it’s very exciting.
This is a chip that might have looked impressive last year, and maybe even today if it had a higher clockspeed and lower price. But that’s not the case, so there’s little reason to consider it. Yes, it has an impressive GPU component. And yes, maybe the Core i5 version has a place as an upgrade from a low-end Core i3-based machine without a discrete GPU. But this expensive and low-performing chip will win few friends among anyone wanting tangible performance boosts over their Haswell.
- Excellent power efficiency
- Impressive low temps
- Great CPU graphics core
- Weak processing performance
- Really high price
- Soon outdated
- Last-gen is mostly quicker
Intel Core i7-5775C Specifications
- CPU cores/threads 4/8
- Process technology 14nm
- Clockspeed 3.3GHz (3.7GHz Turbo)
- CPU architecture Broadwell
- Socket LGA1150