AMD Allegedly Testing Hybrid Processor with Zen 4 and 4c Cores

An unannounced AMD processor identified as Family 25 Model 120 Stepping 0 recently showed up in the MilkyWay@Home database. The CPU can process 12 threads simultaneously and the CPU expert @InstLatX64 believes that this is AMD’s codenamed Phoenix 2 processor, packing two high-performance Zen 4 cores and four energy-efficient Zen 4c cores. 

AMD Eng Sample processor marked 100-000000931-21_N [Family 25 Model 120 Stepping 0] features 12 logical cores (i.e., six physical cores with simultaneous multithreading) and reports about 1MB of cache, which indicates that the MilkyWay@Home client cannot correctly determine the amount of cache featured by the chip. The listing itself does not prove that we are dealing with AMD’s hybrid Phoenix 2 processor with Big.Little-like core configuration, but six physical/12 logical cores featured by an unknown CPU gives us a hint that this may match the rumors.

AMD’s Phoenix 2 processor (which does not have a lot in common with the company’s Phoenix APU) is rumored to feature two ‘big’ Zen 4 cores with 2MB L2 and 4MB L3 cache as well as four ‘small’ Zen 4c cores equipped with 4MB L2 and 4MB L3 cache, which is a rather surprising cache configuration. The APU is also said to pack an RDNA 3-based integrated GPU with 512 stream processors and has a DDR5/LPDDR5X-supporting memory subsystem, according to 3DCenter@InstLatX64 claims that AMD’s Phoenix 2 APU has an A70F8x CPUID, whereas CoelacanthDream asserts that the CPUID of the processor is 0x00a70f80. 

For now, any information about Phoenix 2 in general and the 100-000000931-21_N [Family 25 Model 120 Stepping 0]processor in particular should be taken with a grain of salt since AMD has loads of products in the pipeline. 

The alleged Phoenix 2 processor with two Zen 4 cores and four Zen 4c cores has been running MilkyWay@Home client since early March, which indicates that someone within AMD or even outside of the company is test driving the chip. This may be a sign that the CPU will be released in the foreseeable future, though it is unclear when exactly. Meanwhile, based on unofficial information, AMD is set to release its Phoenix 2 APUs in the second half of 2023.