Discussion How beneficial would it be to have a CPU dedicated on the GPU?

[Gamefreaknet]

Hard to put simply but currently our systems are:
CPU
(assuming its bought) - GPU with vRAM
RAM
Coolers
Case
PSU

However imagine this. A GPU with an inbuilt CPU. Of course this hasn't been done already as both components separately generate a lot of heat however (I personally think) with the high performance AIOs and Air coolers it would be possible to sufficiently cool a GPU that has an inbuilt CPU. On the GPUs backplates for example and a fair few setups would have the room to mount a second AIO or Air cooler and currently (ignoring liquid cooled GPUs) we've only gone so far as triple fan (almost always the fans just facing all one direction).
Since the CPU on our current build isn't directly communicating with the GPU and having to quickly send and receive data which in some cases currently can cause lag in games, rendering etc... (when the CPU has to wait on the GPU to render the frames) a CPU onboard I believe would to an extent improve performance.
To clarify I mean have the CPU on the mobo stay but also have an extra CPU dedicated on the GPU

I am no expert at this so... views on this???

 

[hotaru.hino]

If you're talking about having the main CPU on the video card itself, just so the CPU can talk directly to the GPU, barring the issue that there needs to be a communication standard implemented between them (although pick your flavor between AMD's IF and whatever Intel's is), there wouldn't really be much of a benefit to this. The amount of actual data going between the CPU and GPU, and mind you it's mostly lopsided in the CPU -> GPU direction, is a small amount. The only thing the CPU is doing is telling the GPU what to do.

The only reason why there's lags or latency spikes in a game is there's something else in the system that was so important that the CPU (or maybe the application) had to wait for it, assuming a sufficiently fast enough CPU to keep the GPU busy most of the time.

EDIT: Also fun fact, the Nintendo 64 and Xbox 360 was designed like this. The CPU and GPU were tied directly together, but this led to the problem that the CPU had to go through the GPU to access anything else in the system.

 

[TerryLaze]

Also basically that's what an APU is, both consoles for two generations now have a single chip that is both the CPU and the GPU and shares one pool of ram so that the CPU doesn't have to send the data to the ram first for the GPU to be able to use it.

CPU/GPU in the middle and RAM all around for fastest access.

 

[IDProG]

Hard to put simply but currently our systems are:
CPU
(assuming its bought) - GPU with vRAM
RAM
Coolers
Case
PSU

However imagine this. A GPU with an inbuilt CPU. Of course this hasn't been done already as both components separately generate a lot of heat however (I personally think) with the high performance AIOs and Air coolers it would be possible to sufficiently cool a GPU that has an inbuilt CPU. On the GPUs backplates for example and a fair few setups would have the room to mount a second AIO or Air cooler and currently (ignoring liquid cooled GPUs) we've only gone so far as triple fan (almost always the fans just facing all one direction).
Since the CPU on our current build isn't directly communicating with the GPU and having to quickly send and receive data which in some cases currently can cause lag in games, rendering etc... (when the CPU has to wait on the GPU to render the frames) a CPU onboard I believe would to an extent improve performance.
To clarify I mean have the CPU on the mobo stay but also have an extra CPU dedicated on the GPU

I am no expert at this so... views on this???

What you ask already exists. It's called an APU.

The problems with a desktop APU:

1. It needs a bigger socket size.

2. Desktops don't really need/can't really do it, especially for high-end ones, because it will require MASSIVE die size (even bigger than workstation/server socket)

3. It poses problems with modularity. The beauty of DIY PC building is that you can use any CPU/GPU/RAM that you want. Combining the CPU with the GPU removes modularity, which is not only a negative for the consumers, it is also a negative for manufacturers: It reduces efficiency.
If you notice, the entire Zen 4 architecture only requires ONE type of 8-Core chiplet. This means for a 16-Core, they only need to add 2 chiplets to the CPU die. This is a positive for manufacturers because they don't have to design multiple CPU designs for Ryzen 9, 7, 5, Threadripper, EPYC. Just combine chiplets together. This also makes manufacturers able to repurpose chiplets from less successful products to more successful ones. If the chiplets cannot be repurposed, the less successful products either become e-waste or a bad look for shareholders.

My opinion is that laptops need APUs SO MUCH MORE than desktops do.

I have a feeling that you ask this because of the next-gen consoles narrative. Don't believe it. The difference is in the nanoseconds (and very low milliseconds for the worst case). It won't affect performance by much.

 

[hotaru.hino]

Another alternative interpretation I was thinking of is if there were a CPU in front of the GPU to offload some of the processing the main CPU does.

It still wouldn't help, since the main CPU has to tell the secondary one what to do and it'd make things more complicated on the application side.