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GCN graphics scaled down
Kabini is the first APU to incorporate a graphics block based on AMD's GCN architecture, and this addition grants the SoC a rich suite of graphics- and compute-focused features, including support for the DirectX 11.1 graphics API and the OpenCL media and compute API. Also, crucially, the presence of GCN hardware makes Kabini compatible with the latest AMD Catalyst graphics drivers, which should translate into solid compatibility with the latest applications and relatively frequent driver updates.


Kabini's integrated graphics processor - logical diagram. Source: AMD.

As we've already noted, Kabini's graphics have been scaled down pretty massively in order to fit into the power envelopes in question. The chip has only two GCN compute units, or CUs, with a total of 128 shader ALUs and eight texels per clock of filtering capacity. A single render back-end offers four pixels per clock of blending throughput. For this class of product, these choices are sensible, but we've already established how much grander the scale is in this chip's console siblings. Compare, also, to the Radeon HD 7790; that $149 graphics card has 14 compute units, for a total of 896 shader ALUs, and 16 pixels per clock of ROP throughput. So, you know, don't expect the world from Kabini's graphics, even though they're likely to be the best in their class.

Heck, I'm a little surprised AMD was able to squeeze its full-fat desktop GPU architecture into a chip of this class in any form. AMD has made a few adjustments to adapt GCN to this sort of deployment. This is, in fact, a newer version of GCN than you'll find in most current Radeons; it includes some instructions to facilitate memory sharing between the CPU and IGP. Also, in Kabini, the number of banks in the local data share in each CU has been reduced from 32 to 16. Beyond that, as far as we know, the only other power-saving measures are at the physical design level, where transistor selection was optimized for low-power operation.

Power management
Power management in an SoC like this one is paramount. As AMD's Sam Naffizger told us, if all portions of Kabini were turned on at once in a typical system, it would drain the battery in less than an hour and probably melt part of the system case. These chips can only fit into their prescribed power envelopes by constantly adjusting themselves.

To that end, Kabini has a fairly sophisticated power management setup, similar in basic capability to what's built into AMD's larger Trinity and Richland mobile APUs. At its heart is an onboard 32-bit microcontroller with its own memory that takes inputs from a range of sources across the chip, including power monitors in the CPU cores, the GPU, the display interface, and the FCH. The power controller estimates total power use based on activity and can require an individual unit to ramp down its voltage and clock frequency in order to prevent the chip from exceeding its power budget and overheating.


Power sharing opportunities across the chip. Source: AMD.

Kabini includes power gates for each of its four cores and for its IGP, so power to these sections of the chip can be turned off entirely when one of those entities is idle. The combination of dynamic voltage and frequency scaling, power gating, and intelligent monitoring of power opens up opportunities to share power headroom between different portions of the chip via a mechanism AMD calls Turbo Core. The concept is straightforward: if the GPU is idle and the CPU cores have work to do, the GPU can be shut down and its power budget shifted to the CPU cores. With more headroom, then, the CPU cores can increase voltage and frequency beyond their usual limits.


The user experience is often dominated by the performance of a single core. Source: AMD.

Similarly, a single active CPU core could borrow headroom from its inactive neighbors to range up to higher clocks temporarily. This provision can increase single-thread performance and improve the user's sense of system responsiveness.

All good in theory, right? The strange thing here is that, at launch, only a single model of Temash supports Turbo Core: the 8W A6-1450 quad-core intended for tablets. None of the Kabini-derived parts do. They all can save power via Kabini's DVFS scheme, but they can't shift power around to extract more performance headroom.

AMD does have another trick up its sleeve, also named after forced induction, that may offset any loss of performance from the lack of Turbo Core: it's called Turbo Dock. This feature is intended for dockable tablets like the Asus Transformer series. When the tablet is detached from its keyboard dock, the SoC inside will operate under the burden of a relatively low power limit, to preserve battery life and reduce heat. Once the tablet is docked, the TDP limit is raised, potentially to twice the limit of slate mode. AMD expects to achieve up to ~30% higher performance via this trick. We'll have to see it in action in an actual product, of course, but the theory sounds good.

The products: A- and E-series APUs
Kabini and Temash are code names. Out in the market, AMD will use a different nomenclature to refer to these chips. The Kabini lineup will officially be known as the 2013 AMD Mainstream APU Platform, and it will include both A-series and E-series models, as outlined in the table below:

Model Radeon TDP CPU
cores
CPU
clocks
L2
cache
size
Radeon
ALUs

GPU
clocks

Max
DDR3
speed
A6-5200 HD 8400 25W 4 2.0GHz 2MB 128 600MHz 1600MHz
A4-5000 HD 8330 15W 4 1.5GHz 2MB 128 500MHz 1600MHz
E2-3000 HD 8280 15W 2 1.65GHz 1MB 128 450MHz 1600MHz
E1-2500 HD 8240 15W 2 1.4GHz 1MB 128 400MHz 1333MHz
E1-2100 HD 8210 9W 2 1.0GHz 1MB 128 300MHz 1333MHz

AMD says the A6-5200 will compete against Intel's low-end Core i3 processors, while the A4-5000 will go up against slower Pentium models, and the E-series offerings will stack up against even slower Celerons. The company claims Kabini "completely outclasses" those Pentium processor, and it expects the chip to "dominate" the low-end notebook market.

While those are bold words, AMD touted similar positioning with its original Brazos platform. That was two years ago, of course. Today's Pentiums and Celerons are faster, and Brazos is in no position to match them in a fair fight. Kabini's extra performance should be instrumental in helping AMD recapture lost ground there.

The Temash lineup is known as the 2013 AMD Elite Mobility Platform, and it only includes three A-series models:

Model Radeon TDP CPU
cores
CPU
clocks
L2
cache
size
Radeon
ALUs

GPU
clocks

Max
DDR3
speed
A6-1450 HD 8250 8W 4 1.0/1.4GHz 2MB 128 300/400MHz 1066MHz
A4-1250 HD 8210 9W 2 1.0GHz 1MB 128 300MHz 1333MHz
A4-1200 HD 8180 3.9W 2 1.0GHz 1MB 128 225MHz 1066MHz

In tablets, all three of the A-series chips above will sit between the Atom and the Core i3. In other words, Windows 8 tablets based on Temash should be faster and a little more power-hungry than Atom tablets, but they shouldn't be quite as big, bulky, or expensive as Core-powered slates like the Microsoft Surface Pro. That device isn't so much a tablet as the open-faced sandwich version of an ultrabook.

The A4-1200 has a tighter power envelope than both of AMD's existing tablet chips, the Z-60 and Z-01. Those offerings also have dual 1GHz cores, but they're rated for TDPs of 4.5W and 5.9W, respectively. They also have fewer shader ALUs (80) and less L2 cache (only 1MB) than the new A-series parts. Considering Jaguar's IPC improvements, it's fair to expect the A4-1200 to deliver better CPU performance, better graphics performance, and better battery life than the Z-60 and Z-01.

Temash will also appear in what AMD calls "small screen touch notebooks." In those systems, the chips will again slot in between the Atom and Core series, but they'll have direct competition from low-end Pentium and Celeron processors.