Broadwell: Intel Core i7-5775C And i5-5675C Review

Introduction

The time has finally come for Intel to introduce its socketed Broadwell processors. They’re fabulously late, and you’re probably not going to want to buy them, what with Intel’s Skylake architecture close at hand. But they’re frankly fantastic little CPUs, particularly if you’re a history buff.

What do I mean by that? Well, exactly two years ago, the company was unveiling its Haswell-based desktop processors and Tom’s Hardware’s sentiment was captured somewhat succinctly, I think, by the title of our launch story, The Core i7-4770K Review: Haswell Is Faster; Desktop Enthusiasts Yawn.

Prior to that piece’s publication, I had just spent a couple of days with Intel in Santa Clara learning about its Haswell architecture. Most of the emphasis was (understandably) focused on the mobile effort. We talked about optimizations for power, the Iris Pro Graphics 5200 that’d propel high-end notebook performance forward without a discrete GPU and increased attention on x86 architectures that’d scale down to tablet form factors. It was all well and good. What we saw was exciting, and what we were promised pointed to a future filled with performance-enhancing integration driven by efficiency.

There was just one thing missing, though. Desktop users didn’t get the most exciting goodies. The highest-end socketed CPUs were stuck with decidedly mainstream HD Graphics 4600. Worse, perhaps, the company eliminated the “limited overclocking” previously available on non-K-series models.

What reason did we have to upgrade, then? A little more IPC throughput? Meh. We were underwhelmed, and not particularly subtle about letting Intel know.

Broadwell For Desktop: A Change In The Air?

Massive though the company may be, it isn’t deaf to feedback. Representatives readily admitted it’d be both difficult and time-consuming to incorporate the requests we were making into its stack during the Haswell generation. But it actually did. We wanted a more enthusiast-oriented flagship and it came up with Devil’s Canyon (Core i7-4790K Review: Devil's Canyon Tantalizes Enthusiasts). We asked for a multiplier-unlocked model able to compete against AMD’s affordable Athlon X4s and received the Pentium G3258 (Intel Pentium G3258 CPU Review: Haswell, Unlocked, For $75). Intel even threw HEDT enthusiasts a bone with an eight-core -5960X, plus an attractive six-core -5820K.

Two years ago, I distinctly remember asking about the possibility of a desktop-oriented part with Iris Pro Graphics 5200. This manifested as the Core i7-4770R, and it was great in platforms like Gigabyte’s Brix. But BGA packaging limited its utility to enthusiasts.

This brings us full circle. Intel’s Core i5-5675C and Core i7-5775C are the first socketed desktop processors with Intel’s most advanced on-die graphics engine, Iris Pro Graphics 6200. At last! Both CPUs are compatible with the LGA 1150 interface, supported by existing 9-series motherboards after a firmware update. They’re also multiplier-unlocked, appealing to power users with a penchant for pushing additional performance.

What’s not to like, then? Most pointedly, Intel’s Skylake architecture is expected in a few short months. That’s a “tock” in the company’s cadence, representing a new microarchitecture leveraging the 14nm manufacturing process adopted for Broadwell. Beyond the improvements rolled into Skylake-based processors, Intel’s 100-series chipsets introduce a host of upgrades that enthusiasts will most certainly want (a faster Direct Media Interface, PCIe 3.0 from the PCH and more flexible overclocking on K-series parts—more on all of that later). We typically don’t hold off on recommending hardware, hoping for more from the next generation. But in this case, a distinct lack of interest in Broadwell from most of the system builders we’ve talked to or from Intel itself, really, more than suggests something better is on the horizon.

Still, I can’t help but admire what Broadwell on the desktop achieves. If only for the sake of deconstructing technology and discussing its significance, let’s take a closer look at Core i5-5675C and Core i7-5775C.

Four Cores, Lots Of Graphics And 65W

Both models sport 65W TDPs, so it’s little surprise that Intel says Broadwell is optimized for all-in-ones and mini PCs (though perhaps the soldered-down BGA models will fit better in those environments). Enthusiasts, these aren’t going to replace the Devil’s Canyon processors in your gaming PCs (or even older pre-refresh Haswell-based CPUs). Existing H97 and Z97 motherboards will support Broadwell, provided they receive new firmware. But it’s difficult to imagine a situation where upgrading makes a lot of sense. If you’re on an older Ivy Bridge or Sandy Bridge platform, Broadwell would require buying a new board, doubling your reasons to wait.

In that 65W power envelope, however, Intel crams four Broadwell-based IA cores, a dual-channel memory controller, lots of cache, 16 lanes of third-gen PCI Express connectivity and, most notable, the Iris Pro Graphics 6200 engine, which Intel is confident will circumvent your desire for discrete graphics in the compact form factors it’s targeting.

As host processors, Core i5-5675C and Core i7-5775C should be marginally faster than Haswell-based CPUs at similar clock rates. The issue, of course, is that they employ lower frequencies than a number of previous-gen chips. So, they'll actually post lower scores in workloads that emphasize host processing (like the Sandra Arithmetic benchmark, above). We discussed Broadwell and the process used to manufacture it in Introducing Intel's 14nm Node and the Broadwell Processor. Briefly, though, IPC improvements are only claimed to be around 5%, so performance gains are going to be muted. This is expected on a “tick” cycle; Intel’s focus was on transitioning a mature design to 14nm, after all. The Core i7 does benefit from Hyper-Threading technology, addressing up to eight threads concurrently, while the Core i5 is limited to one thread per core.

The two new BDW-LGA CPUs bear tell-tale signs of a mobile-oriented die configuration (aside from their muscular graphics engines). One is a smaller last-level cache. The Core i5-5675C features 4MB, while the Core i7-5775C comes with 6MB. At least on the desktop, both brands would be expected to sport an additional 2MB.

Then there’s the memory controller with DDR3L-1600 support. Yes, we got away with DDR3 at 1.5V; however, Intel specifies 1.35V modules.

And then there’s the Iris Pro Graphics 6200 engine, Intel’s crown jewel, imbued with more rendering, compute and media horsepower. Architecturally, it’s still an evolution of the HD Graphics design. But the shift to 14nm manufacturing gives Intel room in its transistor budget, opening the door for extra fixed-function and programmable resources. Amazingly, the company more than doubles the shader count of CPUs like Core i7-4770K with Core i5-5675C and Core i7-5775C, while cutting max power by 20W. Iris Pro Graphics 6200 is the GT3e implementation of Intel’s biggest Broadwell die, meaning it’s also accompanied by 128MB of on-package L4 cache. Intel’s API support is extensive, too. The company lists DirectX 11.2 and OpenGL 4.3, adding that it’s DirectX 12-ready and supports OpenCL 2.0, OpenGL ES 3.1 and Renderscript.

As you can see, the Core i7-5775C’s base clock rate is 3.3GHz, and Intel’s Turbo Boost technology pushes the frequency up to 3.7GHz in single-threaded workloads. Again, the CPU includes 6MB of L3 cache and 128MB of eDRAM. Hyper-Threading allows the quad-core chip to schedule eight threads at a time, while official DDR3L-1600 memory support facilitates up to 25.6GB/s across two channels. In a nod to enthusiasts, Intel ships the Core i7-5775C with an unlocked ratio multiplier.  

The Core i5-5675C is also overclockable through an unlocked multiplier — convenient since a 3.1GHz base clock rate and 3.6GHz peak Turbo Boost frequency aren’t that aggressive compared to several existing Haswell-based parts. Still, four Broadwell cores should suffice for all but the most taxing workloads, even if the Core i5 lacks Hyper-Threading support. Intel further differentiates the -5675C’s graphics performance with a maximum dynamic clock rate of 1100MHz for its Iris Pro Graphics 6200 engine, compared to the Core i7’s 1150MHz ceiling.

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