Although AMD doesn’t specifically call it a hybrid core processor, the 4 nm “Phoenix 2” monolithic APU silicon that powers the lower end of AMD’s Ryzen 7040-series mobile processors may very well be the company’s first such processor. When “Phoenix 2” was first hinted at back in July, it was said to be a physically smaller chip than the original “Phoenix.” In contrast to the “Phoenix” silicon’s 8 CPU cores and 12 compute units, it was known to only have 6 CPU cores and a smaller iGPU with 4 RDNA3 compute units. The large drop in device size from 178 mm2 to 137 mm2 at the time was attributed to the absence of 2 CPU cores and 8 CUs, but it turns out that “Phoenix 2” is much more than that.

On the Chinese social networking site QQ, a die photo of “Phoenix 2” was posted, showing two different types of CPU cores. There are actually six cores, but two of them stand out as being bigger than the other four. The logical conclusion from this is that the bigger cores are “Zen 4,” and the smaller ones are the compressed “Zen 4c.” The core machinery of the “Zen 4c” core is identical to that of the “Zen 4,” but it has been rearranged to favor lower area on the die. The “Zen 4c” core runs at lower voltages and clock speeds than the standard “Zen 4” cores, which is the trade-off in this situation. Both types of cores have the same IPC when running at the same clock rates. Additionally, the two have the same ISA, thus any software threads moving between the cores won’t experience runtime issues. AMD can employ a less complex software-based solution than Intel Thread Director to guarantee that the proper sort of workload is allocated to the proper kind of cores and prevent undesired migration between the two types of cores. As opposed to the hardware-based Thread Director, AMD’s technology is upgradable on a regular basis.