AMD 7th-generation APUs focus on mobile performance

The big hype at AMD's Computex event was for the Polaris FinFET GPUs and the forthcoming Zen microarchitecture, of course. While we'll see those products eventually, another AMD product family was actually launched: the so-called seventh generation of AMD Accelerated Processing Units. These new APUs are the products formerly code-named "Bristol Ridge", which we've talked about before. APUs might not be as exciting as new CPU or GPU designs, but these products are a step forward for AMD's mobile offerings.

As it turns out, the 7th-gen APUs come in the dual-module (branded as quad-core) Bristol Ridge design, and a single-module ("dual-core") design called Stoney Ridge. The 6th-gen Carrizo APUs used low-power "Puma" cores for the entry-level Carrizo-L offerings, but this time around AMD is utilizing revised Excavator modules in the whole range. This keeps things simple, with no confusion over what CPU core prospective buyers are getting. Graphics technology in the 7th generation is inherited from Carrizo too, with the new APUs still sporting between 2 and 8 compute units (128-512 SPs) based on the third revision of GCN. That's the design used by the Tonga (R9 380X) and Fiji (R9 Fury X) GPUs, to be clear.

  CPU cores CPU base clock GPU cores GPU clock (max) TDP
FX-9830P 2M/4T 3.0 / 3.7 GHz 8 CUs (512 SP) 900 MHz  25-45W
FX-9800P 2M/4T 2.7 / 3.6 GHz 8 CUs (512 SP) 758 MHz 12-15W
A12-9730P 2M/4T 2.8 / 3.5 GHz 6 CUs (384 SP) 900 MHz 25-45W
A12-9700P 2M/4T 2.5 / 3.4 GHz 6 CUs (384 SP) 758 MHz 12-15W
A10-9630P 2M/4T 2.6 / 3.3 GHz 6 CUs (384 SP) 800 MHz 25-45W
A10-9600P 2M/4T 2.4 / 3.3 GHz 6 CUs (384 SP) 720 MHz 12-15W
A9-9410 1M/2T 2.9 / 3.5 GHz 3 CUs (192 SP) 800 MHz 10-25W
A6-9210 1M/2T 2.4 / 2.8 GHz 3 CUs (192 SP) 600 MHz 10-25W
E2-9010 1M/2T 2.0 / 2.2 GHz 2 CUs (128 SP) 600 MHz 10-25W

So what's new with the 7th generation? Well, a bit. AMD says Bristol Ridge represents a 56% improvement in CPU performance versus 2014's Kaveri, though that number shrinks to about 10% when you compare it to its direct predecessors. A stated graphics performance gain of 37% over Carrizo is likely in part the result of the move to faster DDR4 memory. Those refinements come along with an up-to-12% improvement in power efficiency over the 6th-gen parts. All-in-all, these are the generational improvements we've come to expect from new chips on the same process.

AMD said approximately half the efficiency gains on the new chips came from refinements to the 28-nm process on which they are built, and another 25% from architectural improvements. With Carrizo, AMD debuted a new power management system called Adaptive Voltage and Frequency Scaling, or AVFS. Rather than having to ballpark an acceptable margin for voltage scaling that accounts for variations in manufacturing quality to ensure stability across a product range, Carrizo APUs can test for stability and adjust voltage in real time to find values that suit each specific processor.

This technology is refined in Bristol Ridge with what AMD calls "shadow P-states". AMD's documentation doesn't go into a great amount of detail on the concept, but the gist seems to be that the APU will check itself at POST to determine its own quality, similar to the "ASIC quality" metric that is popular among GPU overclockers. Using that information, the AVFS system can tune both voltage and frequency scaling dynamically to ride the curve and find the highest frequency possible within a given power envelope for any given processor.

Bristol and Stoney Ridge also integrate AMD's "Skin Temperature Aware Power Management" originally developed for the Mullins and Beema low-power APUs. Cyril talked about this concept when those CPUs were revealed in 2014, but essentially the idea is that given a coefficient for how the chassis external temperature reacts to APU power, the APU's power management can regulate the chip's temperature to make sure the device's skin doesn't get too hot. 

On the graphics side, top-end clock rates have been raised to 900Mhz, and support for dual-channel DDR4 memory at speeds up to 2400MT/s will further alleviate some of the bandwidth famine that plagues high-end APUs. Otherwise, the GPU bits of these APUs have been changed mostly in the video engine, with support for hardware decoding of H.264 and H.265 codecs in 4K resolution, and VP9 up to 1080p. There's no word here on encode support, but as these APUs are meant for low-end and mid-range mobile devices, that's likely less of a concern.

Indeed, like Carrizo before it, the 7th generation family of APUs is targeted at laptops. To that end, all of the models have configurable TDPs within a given range. While we were told before that "Bristol Ridge" would be introduced with the AM4 desktop platform that later would see "Summit Ridge" processors based on the Zen microarchitecture, those products are completely absent from any of the material released today.

We won't speculate on why that might be, but part of AMD's presentation this morning was purportedly run from a Zen processor. Meanwhile, AMD says products based on 7th generation APUs should be available now, and indeed HP's Envy 360 convertible equipped with an FX-9800P APU is available now for $679.99. We're looking forward to seeing how the market takes to the new APUs.

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