I'd say PCIe 4.0 arrived about on time. It came to consumer platforms 7 years after PCIe 3.0. NVMe SSDs were just starting to
near the limits of PCIe 3.0, as were GPUs.
When PCIe 4.0 hit, it took SSDs
more than a year to actually show a decent improvement from using it! Even high-end GPUs using PCIe 4.0 showed
maybe a couple % benefit. Even GPUs as powerful as the RTX 4090 were no exception.
When you look at 1% minimums, the assessment doesn't change much. Here's data from their testing of the RTX 5090 on PCIe 5.0:
If you compare the PCIe 4.0 and 3.0 speeds, in that graph, 4.0 is a
whopping 2.6% faster that PCIe than 3.0!
: D
I think we can safely say that PCIe 5.0
was not and
is not necessary, on consumer machines!
PCIe 4.0 arguably solves the problem of making it viable to use x8 or x4 lanes for a dGPU (depending on the performance tier), either because the manufacturer cut the lane count, or because you want to use another PCIe slot or two. However, we should consider that newer PCIe standards require more silicon die area for the PCIe controller, which makes this reduction of lane count a somewhat self-fulfilling prophesy.
The only reason I think we got PCIe 5.0 as soon as we did is that Intel was feeling butt-hurt from getting spanked by AMD and thought they'd up the ante. It's pure specsmanship. It's funny to me how, until
this year, there were no consumer PCIe 5.0 add-in-cards. The
only place consumers were using PCIe 5.0 was in the M.2 slots, which Intel ironically didn't even support until Arrow Lake. ...and the irony doesn't stop there, as Arrow Lake has its own PCIe issues!
In fact, I'd go so far as to say that the
only reason RTX 5000 even supports PCIe 5.0 is for AI! And AMD just added it to try and match Nvidia. Neither of them needed it, for gaming purposes.
If we extrapolate from what happened with PCIe 3.0 -> 4.0, I'd say we shouldn't have had PCIe 5.0 until
next year. That would push PCIe 6.0 out to 2033. Using the figure of 2030 puts us roughly half-way in between a 7 year follow-on from the
actual introduction of PCIe 5.0 and where it should've been. Sounds okay to me.
Then again, it's hard to know exactly what the computing world will look like, in 5 years. Maybe CPUs will all have on-package memory, by then, and CXL memory expansions will be all the rage. That would create a new need for faster PCIe/CXL speeds, and PCIe 6.0 / CXL 3.0 would be the antidote. It'll be interesting to watch.