According to Digital Foundry, PlayStation 5’s APU/GPU will have three different modes to ensure backwards compatibility with the previous generation.
The console’s native mode (“Gen2”) will be blessed with a 2.0 GHz GPU clock, but under the PS4 Pro mode (“Gen1”), the APU will dial down to 911 MHz with 36 compute units (CUs), 218 GB/s of memory bandwidth, and 64 render output units (ROPs).
In PS4 mode (“Gen0”), the processor will reduce its performance even further to 800 MHz and run with half the CU (18) and ROP (32) count.
These metrics are consistent with the capabilities of Sony’s current consoles, which seems to confirm that “Gonzalo” is, in fact, the graphical muscle behind the PS5.
It also alludes to a highly customized contribution from AMD.
The indications are that back-compat is an integral part of the silicon, which in turn raises some interesting questions about the makeup of the Navi GPU and the extent to which older GCN compatibility may be baked into the design.