sounds like either motherboards doesnt support 20x series gpus or raisers do not. I would contact manufactures to be sure they work.
Except that, "For some reason, I can get up to x5 20 series GPUs installed on existing rig builds that already have up to x8 10 series GPUs that were already installed." I recall that such installs often required multiple attempts to take, as in I'd have to try a different x1 slot of MB, but they eventually took, in the past. Stopped at x5 20 series because the rigs became x13 Nvidia GPUs, which is the Windows limit.
So, I've been able to install 20 series on x1 risers of both B250 and H370 Mining MBs of existing builds some weeks to months ago, but installing new 20 series GPUs on new/fresh rig builds on x1 slots has been 100% impossible from my end lately. I've tried adding one 10 series card to quasi replicate the past builds to no avail, even with a 10 series installed and used as video output to display, first 20 series GPU on x1 slot still won't install after dozens of attempts of trying everything under the sun that I can think of.
Recap:
I've successfully installed 15x 20 series GPUs into existing builds, this was 1 month or more ago tho.
12x 20 series are installed into x1 slots of B250 Mining Expert (quantity of 20 series per rig being x5, x4, x3, x1, each rig already had 6 or more 10 series installed)
3x 20 series are installed into x1 slot of H370 Mining Master (quantity of 20 series per rig being x1, each rig already had x8 10 series installed)
Remaining 2x 20 series are installed and running in new rig builds as x1 GPU builds successfully only when installed into x16 slot. Zero progress when trying to install any 20 series into x1 slot of new rig builds of either ASUS B250 Mining Expert & H370 Mining Master motherboards. I thought it was perhaps because of some Windows update that rendered recent 20 series installs into x1 slots impossible (as in over the past few weeks of attempts), or perhaps certain Nvidia driver versions, or a combination of both.
