A few days ago Epic Games released the demo called Lumen which was running on it’s new Unreal Engine 5 on PlayStation 5. CEO of Epic Games, Tim Sweeney went on to explain on Twitter:
Bringing in data from high-bandwidth storage into video memory in its native format with hardware decompression is very efficient.
The software and hardware stack go to great lengths to minimize latency and maximize the bandwidth that’s actually accessible by games.
Those PC numbers are theoretical and are from drive into kernel memory. From there, it’s a slow and circuitous journey through software decompression to GPU driver swizzling into video memory where you can eventually use it. The PS5 path for this is several times more efficient. And then there’s latency.
On PC, there’s a lot of layering and overhead. Then you have the issue of getting compressed textures into video memory requires reading into RAM, software decompressing, then calling into a GPU driver to transfer and swizzle them, with numerous kernel transitions throughout.
Intel’s work on non-volatile NVDIMMs is very exciting and may get PC data transfer on a better track over the coming years.
Industry legend John Carmack, formerly of id Software and now Oculus VR, has agreed with Tim Sweeney:
Yes, being able to load GPU formatted data directly into GPU memory from an SSD is a Big Deal. The only quibble I have with @TimSweeneyEpic ‘s quote is that you can bypass kernel buffers on PC with unbuffered IO. The GPU driver overhead still dominates. https://t.co/lEsdyG8kLY— John Carmack (@ID_AA_Carmack) May 19, 2020
It looks like Cerny has taken the PS5 in a unique direction that PCs may not be able to emulate for a few years it seems. Exciting times!