Everything You Need to Know about APUs in Next-Gen Consoles

By Loyd Case

AMD may not be doing so hot in PCs, but they’re going to rule next gen consoles. AMD’s APUs are what gave them the wins.

As we inch closer to their official announcements, rumors and leaks are coalescing: Sony and Microsoft's next-generation consoles will be powered by AMD processors. More specifically, they’ll be using AMD APUs, aka Accelerated Processing Units. This comes as quite a shock, since both companies had used radically different CPU designs in their current-generation consoles. Sony’s PlayStation 3 incorporated the company’s own Cell processor coupled with an Nvidia-based graphics chip (GeForce 7000 series equivalent). The Xbox 360 uses a triple core CPU based on IBM’s PowerPC processor architecture and a separate AMD-based GPU. But a similar APU design in both next-gen consoles could mean interesting things for gamers. Let's explore the implications.

What’s an APU?

In essence, AMD’s APUs are an ambitious attempt to redefine what a CPU is and its role in a computer. Since AMD’s traditional x86 compatible CPU designs haven’t kept up with Intel on either raw performance or power per watt, AMD is integrating a much more powerful set of graphics cores on the die in an attempt to boost overall performance.

The term “APU” was coined by AMD to describe an x86 processor that includes additional processing capability. At first blush, any CPU that contains a graphics core could be construed as an APU – in other words, it’s an AMD CPU with an integrated graphics core based on AMD Radeon graphics. That’s not conceptually different from Intel integrating their HD series graphics core onto Intel CPUs. AMD argues that the current APUs deserve a different name because their integrated graphics are substantially more powerful than Intel’s.

But AMD’s long term goals are more ambitious. They eventually want to merge the instruction sets for the graphics processor and the CPU, though that will be a gradual evolution over a number of CPU generations.

An AMD APU has several key characteristics:

  • The CPU cores are x86 compatible, so run all PC code.
  • The GPU cores of current APUs are based on AMD Radeon “GCN”, or “graphics core next” architecture, similar to those used in AMD Radeon HD 7000 series graphics cards.
  • The GPU cores are fully DirectX 11.1 compatible, so can run all modern PC games, though with reduced performance compared to desktop CPUs. That means they also fully support all Windows 8 graphics features natively.
  • The desktop AMD APUs use a different socket than more conventional AMD CPUs, socket FM2.

Currently, APUs are used in lower cost PC systems. The top end, quad core AMD A10-5800K costs around $130, which is comparable in price to a dual-core Intel Core i3 [entry level] CPU. Outside of graphics, performance is about the same as that Intel dual-core processor. APUs also show up in budget laptops, like HP’s Sleekbook series, typically costing well under $700. AMD’s Hondo APU, which is targeted at tablets, is being used in Vizio’s upcoming MT11X tablet.

The graphics side of the equation is much different. As an example, that A10-5800K APU sports 384 stream processors (GPU cores). That compares favorably to the budget-priced desktop Radeon HD 7750, which has 512 stream processors. Of course, core clock speeds and memory speeds are different, so the integrated core doesn’t perform as well as a desktop CPU. But it’s still quite capable, especially when compared to Intel's current integrated HD4000 GPU (as found in most Ultrabooks and MacBooks).

The bottom line is that traditional CPU performance is pretty modest when compared to Intel CPUs, but graphics performance is pretty impressive for something built inside a CPU.

Jaguar: The CPU building block for next-gen APUs

Much of the speculation revolving around the new Sony and Microsoft consoles talk about the AMD Jaguar. Jaguar isn’t an APU, however. Jaguar is the AMD code name for the building block that will make up part of an APU – specifically, the part of the APU that looks like a normal, x86 CPU. Jaguar builds in improvements over the previous Bobcat x86 core, as you’d expect. Consequently, Jaguar will be faster in a couple of ways. The core will be able to run at higher frequencies, and more importantly, run more instructions per clock cycle. It also reduces power usage and supports some additional features, like 40-bit physical memory addressing and new instructions.

One of Jaguar’s most important features has nothing to do with its performance. Among AMD's key design goals for Jaguar is to “increase process portability.” What that means is that the ability of different manufacturing plants to take a Jaguar design and actually fabricate it is easier than with past AMD low power cores. This feature makes it attractive to companies like Sony and Microsoft, who will want to shop around for the lowest price for actually building their console processor chips.

AMD will be using the Jaguar core in its upcoming Temash and Kabini quad core APUs. Temash is designed for tablets and very low cost convertible laptops, while Kabini is aimed at budget ultraportable laptops.

The console APUs

The APUs used in the upcoming console designs will be more heavily customized by Microsoft and Sony than the ones you can buy in a PC. According to the rumor mill, both Sony and Microsoft will incorporate 8 Jaguar cores, though at different clock frequencies. The big differences are in the graphics core. Eurogamer posted an in-depth analysis of what’s known about the two different console processors. While raw performance will differ, there are some key differences between the two that may mitigate any performance differences, so that performance from the user’s perspective will be good enough.

First, the target displays seem to be current 1080p HDTVs. By today’s PC standards, 1920 x 1080 is pretty average, and even modest GPUs can drive many games at full resolution and high detail levels at 1080p, particularly if anti-aliasing is disabled. By comparison, the current Xbox and PlayStation render at a lower resolution and then upscale to 1080 using a hardware scaler.

Second, the memory will be radically different between the two systems. Sony’s console looks to have only 4GB of RAM, but it will be ultrafast GDDR5 memory – the same stuff used in modern, high performance PC graphics cards. Microsoft’s console, code-named “Durango”, will double up the memory to 8GB, but it will be slower DDR3 RAM, which will be similar to what’s used for main memory inside a PC. However, the Microsoft console reportedly couples 32MB of ultrafast EDRAM (embedded DRAM) to the GPU, mitigating the slower memory somewhat.

It would be a mistake to compare the GPUs inside next-generation consoles to those inside a desktop graphics card.

Finally, there are differences in graphics horsepower. AMD’s basic building block for its GPUs is the GCN cluster. (GCN, or “graphics core next” is AMD’s term for its latest GPU architecture.) Each GCN cluster contains 64 stream processors, which run graphics code in parallel. Sony’s system will incorporate 18 GCN clusters, or 1152 stream processors. This is comparable to AMD’s current midrange desktop GPUs, the Radeon HD 7850 (1024 stream processors) and the HD 7870 (1280 stream processors.) Microsoft’s system supposedly uses 12 GCN clusters, or 768 stream processors, somewhat more than AMD’s budget-prices Radeon HD 7770, which offers 640 stream processors.

However, it would be a mistake to compare the GPUs inside the consoles to those inside a desktop graphics card. For one thing, the internal GPUs will be closely coupled to the whole system, so overall throughput will likely be higher. Also, the GCNs build into the consoles will probably be customized somewhat, so performance per GCN will likely be different.

What gamers will see

Assuming these rumors are true, most gamers probably won’t notice any performance differences between the two next-gen consoles. That’s because game developers will build their games to target the strengths of an individual console while avoiding the weaknesses. I’m positive there will be differences in image quality between the two consoles running the same game title, but probably nothing radically different.

Maybe the most interesting aspect of these rumors, if true, is that this is the first time a new generation of game consoles will be shipping that offer notably lower CPU and GPU performance than modern PCs. So if you really want the best visual gaming experience going forward, the PC will be the king of the hill.

Is console technology even relevant?

It’s curious that Sony and Microsoft are both pursuing console designs that leverage commodity style PC parts. While the APUs inside the consoles are customized designs, they bear a strong similarity to current PC parts. So the new consoles will likely be cheaper to build at launch than the initial PS3’s or Xbox 360s were back when they arrived.

That may also reflect the changing nature of the game business. Mobile devices and free-to-play games on the PC have stolen much of the audience consoles used to command. On the other hand, the new consoles are look a lot like home theater PCs. That certainly plays into both companies desires to make the new systems stronger media hubs than the current generation. But as gaming systems, consoles will now have to share their audience with smart phones, tablets and even PCs. That’s a seismic shift in the game industry, and how it will shake out is anyone’s guess.

Images courtesy AMD