Discussion How much does the CPU really bottleneck the GPU (from i7-4790 to Ryzen 9 7900)

[Construga]

Hi.

Recently I had to upgrade my old computer and in the process I leaped several generations of processors.
I always wondered how much GPU performance would improve by upgrading the CPU.
On the test bench mark from The Division 2 it just jumped from 78 fps to 100 fps.

I'm happy but I wonder how much of the gain really comes from the CPU. I mean, I had to replace the MB and memory.
This means not only the CPU changed but also that it went from DDR3 to DDR5, PCIe 3.0 to 5.0 (altough the graphic card is only 4.0).

I did jump from an 4th gen Intel processor from 2014 to a current one, but it was an i7-4790 (non-K). Old hardware by technological standards, but I would not call it sluggish (3,6 Ghz, 4 cores + HT.)

Old setup
MB Asus H87-Pro - 2x16 DDR3, PCIe 3.0

New setup
MB Asus X670E-Plus - 2x16 DDR5, PCIe 5.0

 

[Nighthawk117]

It's not just the number of frames you get, it's the consistency between each frame. In your graphs there are fewer and much smaller spikes in the second graph. This would normally translate into smoother motion in games but how noticeable it can be is highly variable. I find it can sometimes be very obvious, in most cases it's more subtle.

The Division 2 also isn't the most demanding game available, run Cyberpunk with all the trimmings and the difference will be night and day. A R9 7900 would be multiple times faster and much smoother when paired with an appropriate GPU.

You chose your parts well, should last you a very long time.

 

[hotaru.hino]

The memory interface shouldn't really be considered, because as CPUs get more powerful, they're capable of churning more data. As a hypothetical, imagine a quad core processor can process say 6 GB/sec of data (which would require 12GB/sec, 6GB/sec each way). DDR3-1600 can certainly handle this. But then you wanted to upgrade to an 8-core processor 10 years later. Immediately you need double the bandwidth to feed the cores, otherwise they'll mostly sit around waiting for data to come to them.

PCIe version only matters if you're going to something like PCIe 1.x. The difference between say PCIe 4.0 and PCIe 3.0 is ~3%, while going to PCIe 2.0 drops it down to about ~10%.

In this case, as mentioned, you're not providing a use case where the new CPU could shine. Though if you really want to see how much the CPU's providing a boost, run with the absolute lowest graphics quality. This shifts the burden of processing more on the CPU than the GPU since the CPU is now forced to spend most of its free time telling the GPU what to do.

 

[geofelt]

Your playing resolution did not change(3440 x 1440)
The stronger processor allowed more frames per second to be generated, but your graphics card is now the limiting factor.
That is typically the case when playing at high resolutions and graphics.