PC Bottlenecks Explained – CPU, GPU, Storage, RAM
|You’ve likely heard the term “bottleneck” before in relation to PC hardware, especially in connection with gaming. You might have even considered what components will be a bottleneck when building or upgrading your system, but what is a “bottleneck” exactly? To keep it simple, it’s when a part in your system is limiting the performance of the other parts. Let me give you an example.
This is a Ryzen 3400G, a quad core CPU using the Zen + architecture meaning it’s basically a 2nd generation Ryzen CPU. I’ve paired it with an RTX 3080, and we are playing at 1080p, using Watchdogs Legion as an easy example. It’s running at 55FPS average, which is decent, but I know this 3080 can do better. I’m going to swap in a 5900X, a 12 core 5th generation CPU using the Zen 3 architecture and runs much faster clock speeds. This is with the same GPU, even the same RAM running at 2800MHz for compatibility with the older 3400G and look, it’s now getting 97FPS average, almost 100% more FPS just by upgrading the CPU!
But it works the other way too, this is the same 5900X but now using an RX 470 4GB. Only 24FPS average, or over 50% slower than the 3400G with the 3080. Ouch. Here’s that in graph form, you can see the 470 is by far slower, despite having the much more expensive and faster CPU. The reason for this is; it’s a balancing act.
Pairing a really high end CPU with a really low end GPU will be dreadful for gaming, and pairing an awful CPU with a really high end GPU isn’t going to be a great time either. Finding the balancing point can be difficult, but let’s do another little experiment that I think will help explain what you should be looking for.
Now we’ve got what is a reasonable system, with an i5 10400F which is a £140 CPU these days, and an RTX 2060. Now this is pretty balanced, and it shows. We are getting 41FPS average in Watchdogs, and it’s a decent playing experience. This is our baseline result – now lets upgrade the CPU, nothing crazy sticking with 6 cores, but now slightly faster with the 11600K.
This is it in, again with the same RTX 2060, and back in watchdogs we are getting 39FPS average, two FPS slower. What? Well, now lets go back to the 10400F, but instead upgrade the GPU. Again, nothing crazy, we are moving up to a 2070 Super. It’s one and a bit tiers up.
So playing with this setup? Much faster. Its 29 FPS faster than our baseline, and 31 FPS faster than our upgraded CPU. The point here is that, for gaming, the GPU pretty much always matters more than the CPU. There are some key exceptions, games like CSGO are a lot more CPU dependant, our first setup with the 3400G and 3080 runs SLOWER than a 5900X with an RX 470! Admittedly, as Hardware Unboxed showcased the NVIDIA driver has a serious overhead with slower CPUs, but it shows there are circumstances where upgrading your CPU may make more sense.
That’s the crux of it – how you balance your CPU and GPU mostly depends on your budget, and your usage. If you only play games, the vast majority of the time your GPU is the thing that matters the most to upgrade, or to spend more on. Sure, if you’ve got a single or dual core CPU from 10 years ago and you are trying to run a 3070 with it, it’s probably time for an upgrade, but any decent CPU from the last 4 or 5 years is going to still be great with most mid range GPUs.
If you also do some streaming or content creation, you’ll need to put a little more emphasis on the CPU, so trading off one tier of GPU for a tier up on CPU might be worth it depending on how often you stream or edit. And if you only work on your machine, generally the GPU becomes relatively unimportant, so spending more on a powerful CPU with a more basic GPU is normally a better way to go.
There are of course plenty of caveats to that, some games are very CPU heavy, so you might find the balance is slightly more CPU – or GPU – heavy. In some creative workloads, GPU acceleration is key, so buying a strong GPU and a mid range CPU might actually make sense, but it depends on the programs you use.
There are also other components that can be bottlenecks in your PC, namely your RAM and storage. The former relates to CPU performance. The faster the ram, and tighter the latency, the quicker your CPU generally is. For Ryzen CPUs, 3600MHz is generally seen as the ‘sweet spot’, anything more and you are wasting your money, anything less and you are starting to give up performance. It’s not a massive gap though, but often the price difference between say 3200MHz and 3600MHz is relatively small, so worth splashing out if you can. It’s not something you would generally upgrade after building though as the cost really isn’t worth the added performance.
For Intel, their warranty says the max you can run on these new CPUs is 3200MHz, although the 10400F is capped at just 2666MHz unless you are on a Z series board and willing to void the warranty. So, if you want to stay “in spec”, those are your limits.
Storage can be a bottleneck too, and may become more prevalent as direct storage access becomes more popular, but for now as long as you aren’t using a 5,400rpm HDD you are generally pretty good. It’s rare that it’d affect FPS though, more things like loading times, which as SSDs are getting cheaper is getting easier to improve.
The takeaway from this video should be; you will always have a bottleneck. There is always something else you can change or upgrade to get more performance. Even with a 5950X and a 3090, when the 4090 comes out, you’ll get more performance out of that 5950X so technically the 3090 was the bottleneck. The point is to balance your system such that you are getting as close to 100% performance out of all of your parts when in use. Most 5th gen Ryzen CPUs perform almost identically in games, so you can happily pair them with any 30 series GPU from NVIDIA or 6000 series card from AMD without much fear of bottlenecking in games.
If you are worried about your setup, here’s a rough guide. If it’s a mid range CPU, so if it’s something like an i5 9400, maybe older i7 like a 4770K, or something like a Ryzen 1600 or 2600, pairing it with a mid range GPU like a 2060, or at a stretch 3060, is going to be a good experience. If it’s a low end CPU like an i3, especially if it’s a dual core, you’ll probably want to only use that with lower end GPUs, like an RX 580 or GTX 1650. And if it’s higher end, use what you like.