PCIe 5.0 is almost four years old and is almost worthless in gaming PCs

Nick Evanson, Hardware writer

This month I’ve been testing: Not much, really! Well, a spot of hidden cable technology by Asus and one of Gigabyte’s latest laptops, but I’m mostly testing a new display panel colorimeter. It’s surprising how much your eyes distract you when looking at a monitor.

PCI Express has been the standard system for sending data and instructions around a computer for twenty years. The specification of how it all works has gone through regular updates, each offering twice the performance of its predecessor. PCIe 5.0 was released almost four years ago and is the latest version you’ll find in any gaming PC right now. It’s also almost worthless, thanks to the disappointing hardware that supports it.

For a computer to support PCIe 5.0, it needs one of two things, but preferably both. First up is the CPU – all of the latest processors from AMD and Intel have built-in PCIe 5.0 controllers. Ryzen 7000-series chips have 28 lanes of Gen 5 PCIe that are divided so that the first 16 are allocated to the graphics card slot, eight are dedicated to M.2 NVMe slots, and the remaining four are used to communicate with the chipset motherboard. (more on that obfuscating mess in a minute).

Intel and AMD’s 14th Gen Core processors have the same number of lanes, but it is divided completely differently. Only sixteen of them are PCIe 5.0 and the rest are the slower 4.0 spec; however, eight lanes are used for the motherboard chipset, leaving scope for one SSD to be directly connected to the CPU. Well, not quite, because the 16 Gen 5 lanes can be switched into 8 + 8 mode, half for the graphics card and half for SSDs (AMD chips can also do this).

Still, on paper, AMD has Intel thoroughly beaten when it comes to PCIe 5.0 support. However, things get more complicated with Ryzen processors because to access the full range of Gen 5 lanes, you need a motherboard that uses E-versions of the latest chipsets. For example, the X670 board will have a PCIe 4.0 graphics card slot and no more than one PCIe 5.0 SSD slot. Change to an X670E motherboard and the GPU slot will be 5.0 and there may be two Gen 5 M.2 slots (although it is usually only one).

If that sounds a little confusing, I can assure you that you’re in a better position than Intel’s current PCIe 5.0 support. Take the ASRock Z790 Nova motherboard, for example. It’s a beautiful board, well built, and has a total of six M.2 SSDs. Two of these are wired directly to the CPU, for best performance, and the one closest to the processor supports a PCIe 5.0 SSD. Unfortunately, if you put at all SSD into that slot, the CPU converts the graphics card slot to eight lanes (aka PCIe x8).

While that still leaves the remaining eight Gen 5 lanes available, they can no longer be shared and since M.2 slots always use four lanes, you’re wasting four PCIe 5.0 lanes by using remove that first SSD slot. Even if you use a Gen 4 or even a Gen 3 SSD. Not all Intel motherboards do this but those using the Z790 chipset and sporting a Gen 5 SSD slot will have this limitation.

But it’s not just the SSD slots that Intel messes up. A single PCIe 5.0 lane has a bandwidth of just under 4 GB/s, so eight of them aggregate to a total of 31.5 GB/s (let’s just call it 32). That’s the same as 16 lanes of Gen 4 so, in theory, fitting a Gen 5 graphics card into an eight-lane slot shouldn’t be a problem.

Except there aren’t any Gen 5 graphics cards – they’re all still using PCIe 4.0, which is better. The next round of new GPUs from AMD, Intel, and Nvidia may move to the newer spec but since they’ve only just switched to Gen 4 in their latest generation of cards, there’s a good chance they won’t.

So, if you’re like me, and you have that ASRock Z790 motherboard, no matter what GPU you use, if you stick an SSD into the first M.2 slot, then the card will be forced to run in PCIe 4.0 mode x8 (same as Gen 3 x16). Fortunately, no game comes close to maxing out the bandwidth of a PCI Express graphics card connection but who’s to say this won’t happen soon?

All these frustrations would be manageable if PCIe 5.0 SSDs were great and worth buying. The reality is that they are a waste of money. Sure, the peak performance in synthetic tests makes older Gen 4 drives look positive in comparison, but in real use, you’ll hardly notice the difference.

That might sound strange, given that one of the few PCIe 5.0 SSDs worth considering has a peak sequential read/write well over 10,000 MB/s – a basic Gen 4 drive will only be half that rate that. The reason is that games, applications, and even entire operating systems have been designed around moving small amounts of data and only when necessary, because most personal computers do not have very fast storage. Gen 5 SSDs can only show their true limits in very specific situations, and few have ever experienced gaming or general computer use.

Then you have price and heat to rub salt into the wound. Head on over to the likes of Newegg and see what real Gen 5 SSDs cost, ie ones that make full use of the connection’s performance. You’re looking at $150 or more for a 1TB PCIe 5.0 SSD and for that amount of money, you can get one of the best Gen 4 2TB drives and still have change.

All Gen 5 SSDs run hotter than Gen 4 ones and it’s not by a few degrees. you at you to use a decent cooling system, either a dedicated heatsink and fans, or a large metal heatsink on the motherboard to absorb and dissipate the heat. In the case of the former, that is an additional cost to consider and depending on the size of your graphics card, you may not have room for it.

It could be argued that this is simply an ‘early adoption’ problem and will only get better as technology advances. While that’s certainly true, it’s worth noting that the PCIe 5.0 spec was released almost four years ago, and AMD’s Ryzen 7000 series hit the market in the second half of 2022. So Gen 5 suffers in really from early adopter problems or is it a case of vendors not being interested in supporting it properly?

It’s a bit of both, to be honest. Each successive revision of PCI Express doubles the amount of bandwidth available to each lane and up to version 5.0, this was achieved by making the bus clocks run twice as fast. Try doubling your CPU or GPU clocks and see what happens. OK, it’s not quite the same thing, but increasing clock speeds significantly, even with a relatively simple system like PCI Express, is no easy task. Electrical tolerances must be extremely tight, which adds to the complexity and cost of everything.

This is especially true for SSDs. To be fully PCIe 5.0 compliant, the controller chip must run faster than a Gen 4 one and the NAND flash memory chips must read and write data at a much higher rate. At the moment, there are few companies that have chips that can do all this and those that can, unfortunately, generate a lot of heat. The market is for Gen 5 SSDs much less than that for Gen 4 drives, so the tiny demand means the relative costs are also higher.

That said, AMD and Intel haven’t done the best jobs in actually implementing PCIe 5.0 – in the case of the former, the Gen 5 graphics card slot is wasted, because no one sells a Gen 5 card, and is the intentional chipset limitation between E and non-E motherboards confusing. It’s also completely unnecessary, as there’s no physical difference between the chips used in, say, a B650 and B650E motherboard.

Intel clearly wasn’t all that interested in Gen 5 PCIe, as its implementation in its 14th Gen desktop CPUs amounts to a 700-series chipset and a PCIe 5.0 x16 slot, a maximum of only one Gen 5 M.2 slot, and a whole set of irritating configuration restrictions . It doesn’t look like Intel will be offering anything much better with Arrow Lake, either.

PCIe 5.0 is pretty much useless right now or at least useless, if that makes any sense. The support for it in the future does not seem much better, either, but fortunately for us, Gen 4 is more than good enough. That technology is coming up to seven years old now but we are still a long way from the point where gaming is limited. At some point, all desktop computers will be completely Gen 5, from top to bottom, but at the rate PCI Express is being implemented, we won’t have to worry about that for a long time.

Let’s hope we don’t have the same problems again but with Gen 7 or similar!