AMD has fully taken the wraps off its brand new seventh generation APU architecture Bristol Ridge, which it announced earlier this year. It promises users around a 20-percent boost in CPU performance and a 37-percent boost in GPU performance over Bristol Ridge's predecessor Carrizo, which launched in 2015. That's standard fare for generational updates, but what's most impressive is that AMD has squeezed this performance out of the exact same architecture as Carrizo: same 28nm transistors, same Excavator-based design.

At the high end are the quad-core AMD FX, A12, and A10 chips, which come in 35W and 15W variants. Base clock speeds are as low as 2.4GHz in the 15W A10 and as high as 3.7GHz boost clock in the 35W FX. The FX and A12 come with up to eight GCN cores in a Radeon R7 graphics package, while the A10 comes with Radeon R5 graphics. All support DRR4 memory up to 2400MHz (versus 2133MHz DDR3 in Carrizo), which should give the on-board GPU a nice boost given how dependent its performance is on system memory.

At the mid to low range are the A9, A6, and E2 APUs, all of which sport a 15W TDP and more conservative clock speeds. Graphics take a cut, too, with the A9 featuring Radeon R5, the A6 Radeon R4, and the E2 Radeon R2. Compared to Carrizo, these low-end chips still get a boost in performance, though, with AMD claiming clock speeds that are 1GHz higher and up to 50 percent more GCN graphics cores. There's also support for HDMI 2.0 (finally), PCIe 3.0, and built-in hardware decoding for MPEG, H.265, and VP9 video up to 4K resolutions.

Performance by process

The question is, if AMD hasn't changed the core architecture of Bristol Ridge compared to Carrizo, just where have the performance improvements come from? The answer lies in a series of subtle improvements rather than dramatic overhauls. According to AMD's Joe Macri, CTO of client products, half of the gains in CPU and GPU performance came from working with GlobalFoundries to improve the existing 28nm manufacturing process.

"We didn't change the shape of the transistor, but we changed transistor implant and gave the transistor much more mobility," explained Macri to Ars. "At any given voltage, we get more current out. It's typically what you'd call a process variant. GlobalFoundries did a great piece of work here. We basically got an extra 200MHz or so out of the core, for a nice 10 percent boost in performance, which is greater than what you typically get out of a simple process tweak. But this wouldn't have made a new product. I wouldn't be calling this a seventh generation product if all we did was get this."

Indeed, AMD also introduced several other tweaks to Bristol Ridge, each of which makes its own small contribution to the overall performance boost. There are shadow processor performance states (P-States), which are two extra P-States based on voltage frequency measurements taken by AMD at manufacturing that allow it to create more accurate clock speed targets. While this means some chips will be more responsive to voltage tweaks than others, overall AMD says that every chip will see some sort of performance boost.

There's a new reliability tracker that tracks how much the chip's transistors degrade due to heat and high voltages, which can cause the chip to slow down. This allows AMD to remove the limitations imposed on every chip in order to safeguard its reliability by tracking instances where heat and voltage are within safe limits, allowing the chip to boost at higher clock speeds for longer.

A new power management feature will use sensors in a laptop to monitor the user's skin temperature, again allowing for higher CPU boost frequencies so long as skin temperature remains within limits. There's even power calibration at boot time that removes the safety limitations associated with variations in consumer power supplies versus those in manufacturing.

The first laptop with one of the top-end Bristol Ridge APUs, the FX-9800P, is already on the market in some versions of the HP Envy x360 convertible. More laptops may follow in the next few months if AMD can secure the design wins.