AMD’s upcoming codenamed Phoenix Accelerated Processing Units (APUs) are set to feature a so-called hybrid design that includes both high-performance Zen 4 cores and energy-efficient Zen 4c cores. Processor programming guide discovered by InstLatX64.
AMD’s Processor Programming Guide clearly shows performance cores marked with 01h and efficiency cores described with 1h. This clearly shows that AMD’s upcoming processors will feature two of his general purpose cores. Given the timing, you’d think we’re dealing with AMD’s codenamed Phoenix processors with Zen 4 and Zen 4 cores, but keep in mind AMD calls them differently.
This document reveals how AMD’s hybrid Big.Little-like design works. As previous AMD documentation pointed out, the company’s high-performance and energy-efficient cores have a different feature set. Therefore, software makers are encouraged to design their programs accordingly.
“Read-only. Reset: Fixed, Xh. Defines architectural feature differentiation (such as microarchitectural resources) per core that can lead to different performance, core clock boosts, and power characteristics,” says AMD PPR. Read the statement.
Of course, a hybrid CPU design would allow AMD’s variants to be more competitive with Intel’s Alder Lake and Raptor Lake parts in the laptop CPU market. Using a hybrid design that includes both high-performance and high-efficiency cores allows AMD to reach performance levels at wattages currently unattainable. Efficient use of low-power cores, on the other hand, depends on software in general and the operating system in particular.
A week ago, when we reported on AMD’s alleged hybrid Phoenix 2 processor, we wondered why AMD would use the same codename (Phoenix APU) for a completely different processor. Apparently, these CPUs aren’t all that different and both feature a Big.Little-like design according to AMD’s programming guide.
Anyway, AMD’s codenamed Phoenix processors are expected to hit the market this year, so expect independent testing of these units at Tom’s Hardware.
