I wonder what they did cut as Cerny specifically mention the CPU had 256 bits operations support (was rewatching the Road to PS5 piece today of all days). I do not think they went with the old two cycle AVX256, 1x256 bits instruction executed as 2x128 bits ones, one per cycle.
Why it would consume a lot less power to process AVX256 with two 128 bits instructions in two cycles than single cycle 256 bits. Still, but confused I will be honest.
Because it means a lot less pressure for the system. But the thing with AVX256 is just a guess. Zen2 is fast, even without that. And AVX instructions are a nice to have. You can do everything even without AVX, but AVX support makes it faster/more efficient. More efficient doesn't mean it needs less power. It needs more in a short time. E.g. Intel CPUs clock themself down into <3GHz territory when AVX(256) is really used and the CPUs still need much power and generate a lot of heat. But you can do it with less power and less heat, but you also need more time.
Heat and power is essential for the PS5, because if the CPU needs more power, it is taken from the whole budget, which means the PS5 GPU must clock down because it has less power available.
If you remove AVX256 from the equation, you might need a bit longer on the CPU side to make your calculations, but you don't need a bigger chunk of the power budget.
AVX instructions are great, but can really hurt your power budget. Btw you need more than 2x cycles if you want to make 256 bit calculations with 128-bit support. But there is a high chance that games won't use those instructions to often, so removing them might be a great way to reduce the overall power-draw of the CPU.
But that is all speculation. And not some dubios insider info
