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Week in Tech: AMD's new single-chip console killer

Kaveri. Heterogeneous computing. Mantle. What? I just want a decent CPU and graphics card, please. Don't know about you, but feels to me like you need a masters in integrated circuit design to keep up with PC processor and graphics tech at the moment. AMD has just outed Kaveri, its latest APU or CPU-GPU thingie. What with all this heterogeneous computing stuff, the promise of Mantle and an integrated graphics core that's not far off next-gen-console performance parity, Kaveri pulls together the tangled web that is AMD's current strategy in a single chip and puts a different spin on what's important in PC processors. It's also bloody confusing. Is Kaveri any good, what does it all mean, should you care, can you even keep up? Answers of sorts I shall provide. Meanwhile, a quick note on Dell and its alleged 30Hz 4K clanger.

AMD Kaveri, then. Let's muscle through the headline specs and features really quickly, just so we all understand what we're dealing with. Then have a stab at explaining what it all means. Some of this is slightly heavy going, but if you haven't already got your head round things like HSA and Mantle, now's the time.

Kaveri is the codename for AMD's latest APU or Accelerated Processing Unit. So, that's CPU and graphics on a single chip. Of course, all Intel's mainstream PC processors have on-chip graphics, too, right down to the poverty-spec models. So simply having on-chip graphics maketh not a revolution in PC hardware.

Significantly, however, most of Kaveri is new – or at least new for an APU. The CPUs cores are brand spanking and constitute a debut for AMD's Steamroller architecture. Then there's the graphics, which is based on GCN or Graphics Core Next.

The Troy McClure of computing
You may remember GCN from such consoles as the Playstation 4 and XBox One. It also stars in all of AMD's latest Radeon graphics cards for PC. It's one graphics architecture to rule them all, essentially.

As for speeds and feeds, we're talking four CPU cores (well, ish) and up 512 GCN stream processors. The latter is a pretty healthy number when you consider the shiny new XBox One has 768 of same. Yup, integrated graphics is edging towards console gaming parity.

AMD's Kaveri: Giving next-gen consoles a kicking. Kinda

Anyway, those new Steamroller CPU cores are claimed to be 20 per cent quicker per thread, per clock. Harrah. Sadly, however, Kaveri is clocked a bit lower than previous APUs – down from a peak of 4.4GHz to 4GHz - so the net result is more like 10 per cent. Haroo.

As for spotting Kaveri with a view to actually buying the bloody thing, you need to look out for an AMD Ax-7xxx chip, for instance the A8-7700K or A10-7850K. The previous generation has Ax-6xxx branding. Not exactly memorable, but there you go. Oh, and you'll need a motherboard with FM2+. Kaveri breaks compatibility with the FM2 socket, sadly.

Hello HSA
So, that's the CPU and GPU covered. Thing is, in some ways it's how those bit work together in Kaveri that is, in theory, the interesting bit. AMD is calling it the first true HSA or Heterogeneous System Architecture chip for PCs.

What on earth does that mean? In really simple terms, it's a chip with different internal components each designed to handle different types of work load. But here's the critical bit. That happens seamlessly and essentially invisibly to the end user. You run an app or a game, threads are generated and they sail through the most suitable part of the chip.

That ought to mean, for instance, almost any kind of floating point operation running on the massively parallel GPU rather than the CPU. Sounds a lot like general-purpose processing on the GPU, you might think. And there is some overlap.


But with Kaveri, AMD has taken it to the next technical level. As for what that actually involves, well, stuff like giving both CPU and GPU full and shared visibility of the entire memory space and interweaving different instruction types as they queue for executing. To be honest, the details probably don't matter. Just understand that there's more to Kaveri than simply sticking CPU and graphics on one chip.

The snag to all this is the requirement for software support. As a general rule, Kaveri's supposed HSA awesomeness won't make the slightest bit of difference to existing games and apps. They'll all need to be tweaked.

More about Mantle
You could say the same about the other big Kaveri-relevant AMD technology, namely the Mantle API or software interface. We've touched on Mantle previously and it remains a tricksy concept to fully pin down. But there are a few key elements to absorb.

Firstly, it's designed to help game developers code specifically for AMD graphics and simply make games run faster. Part of that means making it easier to cook up cross-platform games for consoles and the PC.


Think about it like this. The consoles now have the same graphics architecture as AMD PC graphics. So wouldn't it make a lot of sense if all the effort developers put in to get games humming on consoles paid off for the PC, too?

Mantle's final major feature involves reducing CPU overhead and improving multi-threading in games. It's complicated stuff, again, but take-home message involves the way Microsoft's DirectX D3D API generates CPU-intensive draw calls.

Put simply, with Mantle you can crank out an order of magnitude more draw calls and maintain playable frame rates. That's the claim. So, that might mean thousands instead of hundreds of characters being animated on screen. In other words, forget about the performance boost a really quick new CPU might serve up. You'd need a chip 10 times faster to give you what Mantle enables on your existing CPU.

Well, so the marketing men say. To be fair, early demos of Mantle have looked extremely promising. But just like HSA, the devil will be in the software development. Will enough developers bother to support Mantle to make AMD hardware the default option?

Will any of this actually matter?
In the end, it comes down to a hunch. Personally, I find it hard to believe there won't be some benefit to having AMD PC graphics when running cross-platform games. What I don't fully understand is how much overlap there is between developing for consoles and developing for Mantle. If it's mostly duplication, I doubt Mantle will take off. If much of the work is shared, things will get very interesting indeed.

As for HSA and heterogeneous computing in general, it's been a long time coming. In the long run, it will have a dramatic impact. I reckon that's a given. But I suspect we won't truly begin to feel the effects for a few more chip cycles.

Knee bone connected to the thigh bone?

Oh, as a final note, it's worth pointing out that Kaveri proves AMD's entire experiment with the Bulldozer architecture has been a failure. Kaveri's new Steamroller cores are improved, but not enough to really close the gap to Intel. In pure CPU benchmarks, the fastest quad-core model performs about the same as a similarly-clocked dual-core chip from Intel. Not great.

I'm actually left wondering what Kaveri would look like with some updated Phenom cores with better power gating and maybe a few tweaks to improve performance. Faster than Steamroller, I wager. Despite that, AMD's hardware in general and Kaveri specifically look promising. If HSA and Mantle come off at least in part, AMD hardware is going to look very attractive over the next few years.

I'll admit predicting how all this will shake out it's a very tough call. If I was buying right now, I'd ignore Kaveri or anything AMD and still go for an Intel CPU. But I'd almost definitely pick AMD graphics. They're very competitive as things are. And something spectacular might just happens if Mantle takes off.

4K clanger
Anywho, what about that end note re Dell and the 30Hz 4K clanger? Dell is planning to wheel out a new cut-price 4K monitor. The Dell P2815Q is a 28-inch item that will ship for just $699, which at first sounded bargainous-going-on-bonkers.

But then the realisation it was based on TN panel tech kicked in and it made a bit more sense. As it happens, Lenovo, Asus and Philips (at least, there may be others) have all announced sub-$1,000 (sorry no UK pricing on any of these at the moment) have also announced 28-inch TN ultra-HD screens and it seems likely they all use the same panel.

Anyway, the real killer isn't the TN tech. I'm open minded about that, TN has come on a lot in the last few years and if this new panel is the step forward it's claimed to be, it might be very decent indeed.

No, the real problem is the apparent revelation that the P2815Q is capped to 30Hz running at its full 3,840 by 2,160 pixel resolution. Yuck. I still think there's scope for this being some kind of misquote or cock up concerning the refresh rate running on HDMI 1.4 (only DisplayPort supports that resolution at 60Hz currently). But if it's true, it's a very surprising limitation given that Dell is pitching this screen at least in part as a gaming tool.

I've had a dig around the other brands who've committed to sell similar screens and as yet I can't find any 100 per cent reliable info re refresh on any of them.

Anyway, this curious episode acts as a reminder regards what is actually important in gaming. Is it millions upon millions of pixels? Or is it refresh? In practice, it's obviously both. But if you offered me 2,560 by 1,600 at 120Hz plus G-Sync or 3,840 by 2,160 at 60Hz (forget 30Hz, it's a total deal breaker), it would be a very tough choice. I'd probably take the former for gaming and the later for everything else.

As it happens, I've spent a bit more time larking about with 4K gaming in the last few weeks and I've come away pretty impressed by how the current top end GPUs cope with 4K. You have to be a bit reasonable about some of the IQ settings. But it's actually pretty viable with a single GPU already. I'm just not sure it's actually better than a lower(but still very high resolution) rendered at super-smooth frames rates.

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Jeremy Laird