I don't claim to have the answers.
But my theory is next gen games are not going to be comparable to current gen games in terms of vram and the way it is using it.
Next gen games will be able to stream way more and at a much faster speed from the disk subsystem via technologies such as RTX IO (Direct Storage)
How this will affect vram requirement who knows.
For previous and current gen games which are not engineered to stream from disk and store all their assets in vram then yes vram is going to be a bottle neck.
But next gen games which stream from disk at speeds we currently cannot imagine may not need to store so many assets in memory.
There is an excellent article on the internet explaining how the PS5 does this. I will go and find it.
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Here you go:
"The PlayStation 5 features 16GB of GDDR6 unified RAM with 448GB/sec memory bandwidth. This memory is synergized with the SSD on an architectural level and drastically boosts RAM efficiency. The memory is no longer "parking" data from an HDD; the SSD can deliver data right to the RAM almost instananeously.
Essentially the SSD significantly reduces latency between data delivery and memory itself. The result sees RAM only holding assets and data for the next 1 second of gameplay. The PS4's 8GB of GDDR5 memory held assets for the next 30 seconds of gameplay.
"There's no need to have loads of data parked in the system memory waiting to potentially be used. The other way of saying that is the most of the RAM is working on the game's behalf."
The SSD allows Sony to keep RAM capacity down and reduce costs.
"The presence of the SSD reduces the need for a massive inter-generational increase in size.""
Article
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Also
this should be read as well.
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People thinking that we need 16GB of vram on a gpu to keep up with a next gen console are dreaming.
How do they think the console will power it's self, run it's os let alone run the game even before the topic of vram is even addressed?
The next gen X box has 10GB of FAST ram and 6GB of less fast ram.
My guess is the FAST ram will be used as vram and the less fast ram used for running the console and game ram.
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So it sounds like to me the consoles will be streaming in most of their assets form disk to ram.
And I see no reason why on the 3080 with RTX IO it wont be doing the same. In fact that is EXACTLY it's job and the entire reason it exists.