Intel Haswell: everything you need to know

EXPLAINED Big on power efficiency and graphics, but no more cores

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The IDF Intel techfest is underway, so we can now bring you full details of Intel's next big processor architecture known as Haswell and due out early next year. And surprise, surprise, it's all about power efficiency for mobile devices.

The other big news is that Haswell, also styled as Intel's fourth generation Core processor, will not up the core count for mainstream Intel PC processors. Four is where we're at. Four is where we'll remain. But let's not get ahead of ourselves.

Intel Haswell: architecture

Haswell is a Tock in Intel's Tick-Tock product cadence parlance. That means it's a new architecture on an existing silicon production process. A Tick is a carry-over or only slightly revised architecture shrunk down to a new process.

That makes Haswell a 22nm chip, just like the existing Ivy Bridge family of CPUs, such as the Intel Core i5-3570K. In theory, that's where the similarities end, since Haswell is a brand new architecture, right?

Not quite. Part of the problem is that Intel has already picked all the low hanging fruit when it comes to the basics of its x86 processor architecture. You can only move the memory controller from the motherboard onto the CPU itself once, for instance.

The same goes for integrating a graphics core or adding hardware accelerated video encoding. All of those features appear once again on Haswell, along with HyperThreading, Turbo Boost and the ring interconnect that hooks all those bandwidth-hungry features together.

Intel Haswell: power efficiency

One of the really big differences, then, is power efficiency. Intel is targeting everything from desktop PCs right down to tablets. But it's the latter – the ultramobile market – that's really driving sales growth, currently. And that's what Intel has targetted with Haswell.

In fact, Intel is claiming up to 20 times better power efficiency over the Ivy Bridge generation. Overall, some mobile Haswell chips will creep in under the 10 watts barrier. Incredible stuff, so how is it achieved?

Part of the explanation is a new power state known as S0ix or active idle. It's a sort of hybrid between active and sleep modes. If you think of it as offering the responsiveness of active mode and the power efficiency of sleep mode, you'll get an idea of Intel's intentions here.

Intel says the chip will spend most of its time in this new active idle state, hence the significant impact on power efficiency. That said, we're not expecting battery life to increase by anything like 20 times.

Idle power consumption is just a small part of the overall battery drain on a mobile device. If Haswell improves real-world battery life by 20 per cent rather than a factor of 20, that will be some achievement.

Intel Haswell: CPU performance

Just how much faster will Haswell be than Ivy Bridge? For now, that's very hard to say. Certainly, the basics haven't changed. But some significant tweaks have been applied.

For starters, Haswell gets an extra integer ALU per core and thus can now handle two branches per cycle. Haswell also ups the operations per cycle from six to eight from Ivy Bridge.

Floating point performance also takes a big step forward with the arrival of the AVX2 vector extensions. Both single and double precision floating point operations per cycle are doubled, from 16 and eight to 32 and 16 respectively.

Intel has also cleaned up access to cache memory when executing floating point operations, leading to few cycles waiting for data. That's a change that benefits all floating point workloads, regardless of whether they are coded to support the new AVX2 extensions.

All told, the CPU side of Haswell actually feels more like a Tick or minor transition than a major architectural Tock. We'd be happy to be proved wrong, but we doubt performance on the CPU side will be dramatically improved.

There's no word as yet on clockspeeds. But again, we're not expecting anything hugely different from existing Intel Core chips.

Intel Haswell: graphics

At ground level, Haswell graphics is nothing new. It's pretty much the same design as Ivy Bridge's integrated graphics core. The difference is scale.

Haswell graphics will be available in three versions, GT1, GT2, GT3 and the difference comes down to functional units and performance. The GT3 core pretty much doubles up on everything when it comes to computational hardware.

We're still not clear on how many execution units GT3 in Haswell has, thought the strong money is on 40 versus 16 for the fastest Ivy Bridge chips. But Intel has been showing off Haswell at IDF running games at around twice the speed of Ivy Bridge graphics. And without any increase in power consumption.

Haswell still won't be competitive with high performance discrete graphics. But with Haswell, we could be at the point were integrated graphics is OK for most games. If that's the way it turns out, it will be big news indeed.

Intel Haswell: verdict

Slightly better CPU performance and dramatically better graphics combined with much improved power efficiency. That's the overall gist for Intel's Haswell chips.

Admittedly, we're a little disappointed about the CPU side from what we've learned. But not surprised. PC processors have been at or at least close to "good enough" for several years. It's power efficiency and graphics Intel needs to improve.

That's exactly what Haswell delivers. It's not hard to imagine a tablet convertible PC based on Haswell with performance to match a current mid-range desktop system becoming available next year. Definitely something to look forward to.