AMD Ryzen 4000 mobile APUs already arrived this year, but according to a tweet from hardware detective @_rogame, it's possible we'll soon see AMD Ryzen 4000 APUs make their way to the desktop with AMD's Zen 2 microarchitecture.
AMD has pretty much flushed out its processor product stack with 7nm parts. Only the desktop APU hasn't received the Zen 2 treatment. AMD's current desktop APUs, (codenamed Picasso), are still on the Zen+ microarchitecture and GlobalFoundries' 12nm manufacturing process. The transition to Zen 2 and the 7nm process node would bring some significant improvements to the segment.
The unidentified processor's core and thread count is currently unknown, but it reportedly runs within the 35W envelope. Given the TDP rating, it could be an Athlon or one of those Ryzen 3 or Ryzen 5 GE-series parts that are optimized for efficiency. For context, existing Ryzen desktop APUs span up to four cores, while Athlon chips are stuck at two cores. The hardware sleuth seemed to think that the processor could be the Ryzen 3 4200GE or Ryzen 3 4100GE.
According to the tweet, the CPU features a 3 GHz base clock with performance somewhere between a Ryzen 5 4600U and Ryzen 7 4700U. The hardware detective didn't share the exact design of the iGPU; however, it was seemingly operating with a 1.2 GHz clock speed. Graphics performance was allegedly slower than a Renoir chip with six Vega Compute Units (CUs).
The desktop AMD Ryzen 4000 APU was reportedly tested with a system using an AMD motherboard that appeared under the "Artic" codename, which could point to an unreleased chipset. The processor was paired with DDR4-3200 RAM, so there's no doubt that it's a desktop processor. In any case, the APU should be backwards-compatible with AMD's 300-and 400-series motherboards with a mere firmware update.