Phoenix2: AMD’s First Hybrid Processor Combines Zen 4 with Zen 4c in Stealth

"Phoenix2": AMDs erster Hybrid-Prozessor kombiniert heimlich Zen 4 mit Zen 4c

AMD appears to have quietly released another combination processor within the Zen-4 generation, but is keeping its existence hidden. Phoenix2 is the younger sibling of Phoenix, which is primarily used as Ryzen 7040H and 7040U in notebooks. The big difference is that Phoenix2 is likely AMD’s first hybrid processor with different core types.

Die-shots show two full Zen-4 cores, which are found in all other Ryzen processors. Additionally, there are four Zen-4c cores, which AMD only previously used in the server processor Bergamo. The four Zen-4c cores take up slightly more space than two Zen 4 cores. In addition, there are four RDNA3 compute units (256 shader cores), a 128-bit wide memory interface for DDR5 and LPDDR5 RAM, presumably 14 PCI-Express 4.0 lanes, and plenty of USB.

Despite the differences in cores, Zen 4c has the same functionality as Zen 4. Both types have the same number of internal compute units and the same size level-1 and level-2 caches. They also both support simultaneous multithreading (SMT). AMD achieves the reduction in size primarily through a more relaxed clock curve. Zen-4c cores have lower clock speeds, allowing for a more compact design with fewer filling transistors. AMD also uses more compact SRAM cells for the caches.

A member named “HXL” shared a die-shot from a Chinese messenger platform, which was then labeled in the 3DCenter-Forum. In July, a member on the Chinese Bilibili forum shared an image of a presumed Phoenix2 processor. Its size is estimated to be just under 140 mm², compared to Phoenix’s 178 mm².

First test results have been published by “David Huang” on the Chinese platform Zhihu. He claimed to have tested a Phoenix2 processor, which is said to be featured in the Ryzen Z1 handheld console, possibly Asus’ ROG Ally in a future, more affordable version. Allegedly, AMD plans to use both Phoenix2 and Phoenix, along with Ryzen 5 7540U and Ryzen 3 7440U, in the Ryzen Z1. The test confirms that Zen 4 and Zen 4c have the same clock speed. This supports AMD’s statement that the two core types are identical apart from the clock frequencies. A Zen-4c core reportedly requires less electrical energy than a Zen-4 core up to 2 GHz.

However, the voltage requirement increases significantly beyond 2 GHz, making Zen 4c less efficient. At its peak, Zen-4c cores can reach 3.5 GHz. It is important to note that the voltage curve is not set in stone and firmware updates could change its behavior. AMD’s communication regarding Phoenix2 raises questions. Even during the presentation of Ryzen Z1, Phoenix2 was not mentioned. The company also deflects inquiries about Phoenix2 or hybrid processors.

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