Why does the RTX IO in the Nvidia GeForce RTX 30 Series use any CPU at all even though the information flow from the storage to the GPU?

Question

I saw in the 2020-09-01 Official Launch Event for the NVIDIA GeForce RTX 30 Series that the RTX IO in the Nvidia GeForce RTX 30 Series allows the GPU to directly access the storage (SSD) without having to go through the CPU, as shown in the flowcharts below.

In the Nvidia GeForce RTX 20 Series and before, the information from the storage goes through the CPU before reaching the GPU (flowchart from the Official Launch Event linked above):

In the Nvidia GeForce RTX 30 Series, the information goes straight from the storage to the GPU:

How ever I see on the same slide "20x lower CPU utilization":

Why does the RTX IO in the Nvidia GeForce RTX 30 Series use any CPU at all when information flow from the storage to the GPU, since according to the flowchart the information goes straight from the storage to the GPU?

Answer 1

According to the flowchart the data goes straight from storage to the GPU?

CEO Jensen Huang didn’t go into much detail, but Nvidia’s RTX IO technology puts the speed of PCIe 4.0 storage to more efficient use, sending some loading and texture data over the PCIe 4.0 connection of the GeForce RTX 30-series GPUs to tap into their blazing-fast onboard memory--rather than routing all that information through the CPU first, "

^{(emphasis mine)}

Note he says some not all.

Source Nvidia GeForce RTX 30-series GPUs: 5 things PC gamers need to know | PCWorld

There is a lot more information in the Nvidia Developer Blog. See GPUDirect Storage: A Direct Path Between Storage and GPU Memory | NVIDIA Developer Blog

Note also that:

RTX IO and DirectStorage will require applications to support those features by incorporating the new API’s. Microsoft is targeting a developer preview of DirectStorage for Windows for game developers next year

Source GeForce RTX 30 Series Community Q&A: You Asked, We Answered

So the whole concept relies on Microsoft releasing the Direct Storage API sometime next year. Then the game developers have to start using it. Right now it is just marketing hype.