The problem is, that HBM2 + DDR4 has not the same bandwidith.
24GB GDDR6 RAM 14Gbps on a 386bit bus has a total bandwith of 672GB/s
HBM2 in a 2 stack (2*4GB) configuration at 1000MHz on a 2048 bit bus has a total bandwidth of 512GB/s
So you still need 160GB/s bandwidth with your DDR4 RAM solution to match GDDR6
And that would be a 256 bit interface with 5000MHz DDR4 RAM (8* 2GB)
HBM makes sense. HBM in combination with DDR4 does not make sense, unless you're okay with less total bandwidth.
And only in that case would you save any significant power savings over GDDR6 only.
But that's the point. You can take a marginal hit in total bandwidth if there are other benefits, like less bandwidth contention from the CPU, lower overall power, etc. And technically speaking, you are ignoring scenarios where the HBM could offer up to 1TB/s bandwidth with very little additional power use, in which case the GDDR6 would be at a significant bandwidth disadvantage. Not saying that is likely in the PS5, but your claim that you can't get the same bandwidth at the same power cost is just false.
Gonzalo was said to have Navi 10 lite.
So 36-40 CU with ~1800 mhz.
That being said the addition of RT and the rumors of high tfs in PS5 makes me doubt Gonzalo was PS5.
We've never confirmed anything about "Navi Lite", let alone any details on how many CUs that Gonzalo would have.
I just randomly saw that on Twitter. Anybody knows what this means?
Just speculation, but I don't doubt it.