I’ve gotten a bit overwhelmed by all the block diagrams and shared resources on the X870E boards. Was hoping to get some guidance on what mobo (maybe X670E?) would be best for a setup that would allow for full 16x on the PCIE, 8x on another PCIE, and as much 3.2 gen 2 bandwidth as possible for external capture devices. Don’t think I’d need more than 2 M.2 slots.
was looking to eventually equip it with:
9950X3D
GTX 5090 (would require unshared 16x PCIE?)
ideally an 8X PCIE slot for a quad port HDMI capture card
and support for several 3.2 gen 2 devices that will probably saturate most of the bandwidth ( Elgato 4k X capture devices)
Not sure an X870E exists that has PCIE slots that can run both 16X and 8X at the same time, but maybe I can compensate for that if there’s a board with a bunch of lanes dedicated to USB bandwidth? I figure at some point in the future USB 4.0 might be useful, but it isn’t right now.
Two USB 4 USB-C ports that don’t share bandwidth with other devices
No, the 5090 won’t struggle in a x8 slot since it will use PCIe Gen5 which has the same bandwidth as PCIe Gen4 x16. Blackwell is the first NVIDIA dGPU generation using PCIe Gen5.
I’d get ECC memory for such a build to reduce the risk of potential stability issues.
You won’t get more out of current AM5 platforms, Zen 6 might upgrade the CPU-Chipset Interface to PCIe Gen5 x4 with the X1070E (?) chipset, currently it’s still Gen4 x4.
Do note that these share bandwidth with the second gen5 m.2. It takes away 4 of the 16x/8x8x lanes, so with it in use you can only get x8x0 or x8x4 on the two top slots… The first m.2 does not share bandwidth. The third and fourth share bandwith with all of the USB and the third (chipset) slot. The USB4 ports have their own (cpu connected lanes).
I’d leave M2_2 empty then to keep the main PCIe slots at x8-x8 and use M2_3 and M2_4 via the chipset, if more than one M.2 SSD is needed (M2_1 doesn’t share any bandwidth).
Quad HDMI capture cards are likely only PCIe Gen3 x8, reducing it to a x4 interface might cause issues with 4 UHD inputs.
Really appreciate all the great info, so even using two M.2. slots would potentially take away from the non-USB 4.0 bandwidth
If I were to ditch the 2nd card for QUAD HDMI - is there a board out there with a lane setup that prioritizes USB bandwidth? For example, maybe I just attach 5 Elgato 4K X devices?
Right now on my X570 board, I have my internal Quad 4K card, and one external 4k X
You can connect the USB devices to the USB 4 ports of the ProArt X870. The USB 4 controller on the motherboard has dedicated PCIe lanes to the CPU, meaning these USB devices never have a situation where maybe another device is stealing their bandwidth, causing stuttering etc.
USB 4 ports can be used for USB 3.2/3.1/3 devices just fine.
With that configuration the only device using Chipset bandwidth (which is PCIe Gen4 x4) would be the second M.2 SSD and around 6,500 MB/s are no problem here.
With what you’ve described an HEDT platform is unnecessary and be aware that HEDT tends to be a bit more “sensitive” compared to mature mainstream platforms since the volume of mainstream platforms is on a different order of magnitude and manufacturers direct more resources there to fix bugs etc. Just look at the frequency of BIOS releases for AM5 and Threadripper motherboards and no, Threadripper platforms aren’t “perfect”, not needing any fixes at all.
And if possible only use two memory modules, not four (2 x 48 GB ECC UDIMM so 96 GB in total, individual 64 GB UDIMMs should be released in 2025 for 2 x 64 GB), using four DDR5 UDIMMs on AM5 is more difficult for the AM5 CPUs’ memory controllers than using four DDR4 DIMMs on AM4 leading to significantly lower memory frequencies in practice. That sucks a bit.
Just to be sure since when you’re not familiar with that matter and are looking for ECC UDIMMs it might happen to accidentally get incompatible “Registered” DDR5 RDIMMs that work on server platforms only, not the “Unbuffered” ones that are required on mainstream platforms.
My recommendation for AM5: Kingston KSM56E46BD8KM-48HM 48 GB DDR5-5600 ECC UDIMMs
x8 / x8 gen 5 would probably fine for both a 5090 + a capture card.
Yeah probably if a 4x gen3 link would have been sufficient.
Than a board like the Asrock X670E Steel Legend for example could have been ideal.
Because the second pci-e slot is a 4x gen3 directly wired into the cpu.
So it does not share lanes with the main pci-e slot.
However yeah if 4x gen3 won´t cut it that the best option would be a x8 / x8 configuration.
Or a HEDT platform which has sufficient lanes for x16 / x16 configuration.