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>Fortunately, those extra PCIe lanes tend to get repurposed as additional M.2 holes. Or unfortunately, for the unlucky people who didn't do their research, so
by viccis 2y ago
>Fortunately, those extra PCIe lanes tend to get repurposed as additional M.2 holes.
Or unfortunately, for the unlucky people who didn't do their research, so now their extra M.2 drives are sucking up some of their GPU's PCIe bus.
- Numerlor 2y agoThe vast majority of people run just one gpu, which motherboards have a dedicated direct to CPU x16 slot for. Stealing lanes comes into play with chipset connected slots
- doubled112 2y agoThe real PITA is when adding the NVMe disables the SATA ports you planned to use.
- creatonez 2y agoDoesn't this usually only happen when you put an M.2 SATA drive in? I've never seen a motherboard manual have this caveat for actual NVMe M.2 drives. And encountering an M.2 SATA drive is quite rare.
- ZekeSulastin 2y agoI have a spare-parts NAS on a Z170 (Intel 6k/7k) motherboard with 8 SATA ports and 2 NVME slots - if I put an x2 SSD in the top slot it would disable two ports, and if it was an x4 it would disable four! Luckily the bottom m2 slot doesn’t conflict with any SATA ports, just an expansion card slot. (The board supports SATA Express even - did anything actually use that?) SATA ports are far scarcer these days though and there’s more PCIE bandwidth available anyways, so it’s not surprising that there aren’t conflicts as often anymore.
- toast0 2y agoNope, for AM5, both of the available chipsets[1] have 4 serial ports that can be configured as x4 pci-e 3.0, 4x sata, or two and two. I think Intel does similar, but I haven't really kept up. [1] A620 is cut down, but everything else is actually the same chip (or two)
- zten 2y agoI bought a Gigabyte X870E board with 3 PCIe slots (PCIe5 16x, PCIe4 4x, PCIe3 4x) and 4 M.2 slots (3x PCIe5, 1x PCIe 4). Three of the M.2 slots are connected to the CPU, and one is connected to the chipset. Using the 2nd and 3rd M.2 CPU-connected slots causes the board to bifurcate the lanes assigned to the GPU's PCIe slot, so you get 8x GPU, 4x M.2, 4x M.2. I wish you didn't have to buy Xeon or Threadripper to get considerably more PCIe lanes, but for most people I suspect this split is acceptable. The penalty for gaming going from 16x to 8x is pretty small.
- elevation 2y agoEven with a Threadripper you're at the mercy of the motherboard design. I use ROG board that has 4 PCIe slots. While each can physically seat an x16 card, only one of them has 16 lanes -- the rest are x4. I had to demote my GPU to a slower slot in order to get full throughput from my 100GbE card. All this despite having a CPU with 64 lanes available.
- nrdvana 2y agoYou're using 100GbE ... in an end-user PC? What would you even saturate that with?
- aaronmdjones 2y agoI wouldn't think it's about saturating it during normal use; rather, simply exceeding 40 Gbit/s, which is very possible with solid-state NASes.
- Dylan16807 2y agoOkay, but then I need to ask what kind of use case doesn't mind the extra latency from ethernet but does care about the difference between 40Gbps and 70Gbps.
- grw_ 2y agoI don't think Threadripper platform is to blame that you bought a board with potentially the worst possible pcie lane routing. Latest generation has 88 usable lanes at minimum, most boards have 4x 16x, and Pro supports 7x Gen 5.0 x16 links, an absolutely insane amount of IO. "At the mercy of motherboard design"- do the absolute minimum amount of research and pick any other board?
- viccis 2y agoAs some others have pointed out, there are some motherboards in which, if you use M.2 cards on the wrong slot, it will turn your 16x GPU slot into 8x.
- throwaway48476 2y agoNew chipsets have become PCIe switches since broadcom rug pulled the PCIe switch market.
- gruez 2y ago>broadcom rug pulled the PCIe switch market. What does this mean? Did they jack up prices?
- nyrikki 2y agoAvego wanted PLX switches for enterprise storage, not low margin PC/server sales. Same thing that Avego did with Broadcom, LSI, Brocade etc... during the 2010's, buy a market leader, dump the parts that they didn't want, leaving a huge hole in the market. When you realize that Avego was the brand produced when KKR and Silver Lake bought the chip biz from Agilent, it is just the typical private equity play, buy your market position and sell off or shut down the parts you don't care about.
- b112 2y agoWhen the LSI buy happened, they dumped massive amounts of new, but ptior gen stock into the distributor channel, then immediately claimed them EOL. Scumbags.
- crote 2y agoI wish someone bothered with modern bifurcation and/or generation downgrading switches. For homelab purposes I'd rather have two Gen3 x8 slots than one Gen5 x4 slot, as that'd allow me to use a (now ancient) 25G NIC and a HBA. Similarly I'd rather have four Gen5 x1 slots than one Gen5 x4 slot, as Gen5 NVMe SSDs are readily available and even a single Gen5 lane is enough to saturate a 25G network connection and it'd allow me to attach four SSDs instead of only one. The consumer platforms have more than enough IO bandwidth for some rather interesting home server stuff, it just isn't allocated in a useful way.
- Calwestjobs 2y ago
- Calwestjobs 2y agoyou can run your GPU in x4 and your eyes wont see difference, EDIT: yes.
- lillecarl 2y agoLuckily unless you're doing something odd with your GPU it isn't using the bandwidth and won't lose significant performance either way. Steve from gamers nexus tests new GPUs on older PCIe gens and the difference is negligible. And since PCIe always doubled bandwidth with generations it's effectively the same as running on half bus speed. I run an Intel A380 for Linux and a NVIDIA 3060 for a Windows VM (I'm a bit cheap). I opted for using some Intel SATA6 datacenter drives we decommissioned from work over using more PCIe for storage, but the performance is outstanding. Modern game engines don't need all those gigabytes per second. If you're doing AI maybe it matters, but then you probably hopefully maybe won't cheap out on consumer CPUs with 20 PCIe lanes either.
- wtallis 2y agoLow-end GPUs often only have eight PCIe lanes to begin with, sometimes because they're using chips that were designed more for laptop use than for desktop cards. Intel Arc A380 and B580, AMD 7600XT, NVIDIA 4060Ti and 5060Ti are all eight-lane cards.
- adgjlsfhk1 2y agoI do really think we're due for an expansion refactor. 75 Watts is an awkward amount of power and PCBs are worse than wires for data throughout and signal integrity. It feels like GPUs would be much happier if we just had a cable to plug into the motherboard that transferred data and no power and which didn't force the GPU to hang off the side of the motherboard and break during shipping