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0 pointsgreycol2d ago0 comments

The PCIe lanes are the worst. You have x16 slots that run x1, you need to check slots with m.2 to make sure an x8 doesn't become x4 if you insert storage. Wait if I plug something into the thunderbolt port my 10g network card runs at half speed? Obviously these are actual physical limitation from PCIe lane counts, but it makes it impossible to search. Just painfull.

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chainingsolid2d ago

My advice to anyone doing motherboard shopping is to read the manual off the manufacture's site before deciding. The pcie lane tradeoffs tend to be in the block diagram next to the contents page.

post_break2d ago

This is exactly why my comment goes over the head of people who cry just get the basic boards. No, this is why the basic boards for $100 don't cut it. You now need to dive into the technical data and realize that the $100 board seems like a deal for a reason, and suddenly the $300+ category is your only option if you want to get a PC that doesn't run on fake specs.

dangus2d ago

I'm just struggling to figure out how many people actually need the PCIe lanes for anything more than GPUs and storage, though.

Like, what are you actually connecting your desktop to?

The only reason laptops depend on Thunderbolt is because they have limited internal expansion and need high performance external I/O.

If you need more things than gaming boards offer then obviously you have very advanced needs and can go pay for a workstation board, something like an sTR5 socket Threadripper board.

_factor2d ago

They exist to partition capability so that enterprises can’t connect all of their peripherals and some ECC memory to get the same functionality for 1/10 the price. It’s not a physical limitation.

greycolOP2d ago

Obviously market tiering is part of it and you can play tricks with north and south bridge and pcie switches (which adds cost), but a ryzen board that advertises a pcie 5.0 x16 gpu slot and 5.0 x4 m2 slot only has 4 lanes left to work with from the cpu (i.e the cpus only have 24 usable lanes). Which while you can play with generations to get more lanes it's effectively still 16gb/s. That needs to cover network, extra m2 slots, usbs, as well as the extra PCIe slots.

I don't mind having to work within those physical limits but I do want to be able to search for boards that support N components. i.e 1x 4.0x8, 2x 3.0x8, 4x 5.0x4 . But the best you can search for is physical sizes of pcie slots and then dive into a spec sheet for each one, only to find that the 6 x16 slots only have 1.0x1 of bandwidth each.

dangus1d ago

I think the biggest aspect is that there’s so little demand for the configuration that you’re looking for.

Most people only need the PCI lanes for graphics cards and storage. There aren’t many other internally installed devices out there that actually need that kind of bandwidth, and a lot of those use cases are already covered by alternatives like Ethernet or USB, or they’re already on your board (m.2 slots, fast Ethernet ports).

The 6x16 slots with 1.0x1 bandwidth are there so that people can plug in stuff like sound cards and other random stuff that generally has pretty light bandwidth needs.

If I just search for “PCIe card” on Newegg most of the resulting products max out at x4, and most of the ones that do are already on the board (m.2 cards, additional USB/Thunderbolt).

The one use case that seemed useful and unusual in my search results was a quad port HD video capture card which seemed to require x4 bandwidth.

If you had a scenario like you describe where there isn’t a single x16 slot, you’ve instantly annoyed 95% of the market that needs that full bandwidth for a GPU, whether it be for gaming or for professional applications.

Some solutions that avoid expensive workstation boards and CPUs include getting a higher end chipset to get gaming boards that come with 2x x16 slots, or you can use accessories and adapters that just plug into m.2 slots.

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