AMD’s first hybrid core processor, also known as big.LITTLE in Arm terminology has been spotted for the first time, courtesy of 金猪升级包. Codenamed Phoenix 2, these APUs will comprise the Ryzen 7040 family with a smaller die area and improved power efficiency. In the below shot, you can see vanilla Phoenix on the left and Phoenix 2 on the right. Thanks to the smaller Zen 4c cores, the latter is ~23% more compact than the former:
As reported multiple times, AMD’s approach to a heterogenous core architecture is much simpler than Intel’s. Instead of using a completely different ISA (like Intel’s Monts), AMD has decided to shrink its existing Zen 4 core. This confers the same advantage: reduced die space and improved power efficiency without the challenges of maintaining a second ISA.
According to @BusAlexey (Twitter), the Phoenix 2 top-end die is dual-sourced. This means some will consist of fully enabled Phoneix 2 dies, while the rest will be derived from cut-down Phoneix dies. The Zen 4c cores on the Phoenix 2 dies are simply stripped-down Zen 4 cores running at lower clocks. It’s unclear whether the L3 cache has been further reduced or the floorplan optimized for die space.
Regardless, this arrangement allows AMD to downclock some of the cores on the Pheonix chips and brand them as Phoenix 2. The Ryzen 5 7540U will be the top-end Phoenix 2 chip. It will feature two Zen 4 cores capable of high-core clocks and four Zen 4c cores running at tame clocks for power efficiency.
It’s worth noting that these likely aren’t the same Zen 4c cores we saw on the Epyc Bergamo chips. Each of those CCDs consists of 16 cores, twice as many as normal Zen 4 CCDs. The Phoenix 2 CCD is likely just a repurposed 8-core CCD. In the future, we may see similar designs for mobile Ryzen parts with a mix of 8-core and 16-core CCDs, but we can’t confirm anything.
In addition to the 6 cores and 16 threads, the Phoenix 2-based Ryzen 7540U will consist of 4 RDNA 3 Compute Units. That’s a fraction of what the top-end Phoenix chip sports (up to 12 CUs), but it makes sense considering the reduced die area.
The AMD Ryzen Phoenix 2 mobile processors will land close to the holiday season. Expect a limited volume, with some earmarked for handhelds and custom OEM notebooks.