Hi,
so I found a possible solution for the said problem.
Problem
Gigabyte Fintech 12 GPU B250 mining mainboard does not boot / post after connecting more than 9 GPUs.
It does not depend on which PCIe slots you use, just disconnecting any card helps, as long as there are no more than 9 connected.
Intro
.. As stated, if the problem solves by disconnecting any of the cards so that there are only 9 connected, you can quickly check if you have that specific problem. There is still a possibility, that your PSU is the problem, especially, if you built a new rig and boot up for the first time. Maybe your rig just draws too much power.
.. It still might be a riser, although you ruled that one nearly out by confirming it is not related to specific GPUs.
.. Might still be a defective component on the board.
Steps done before in no particular order, that were not related to the solution and did not solve the problem
.. Switched RAM and CPU
.. Switched RAM slots
.. Loaded defaults in BIOS
.. Reflashed recent BIOS
.. Flashed old v3 BIOS
.. Checked every setting and deactivated all unneccessary devices
.. Mining mode is enabled, 4G decodeing is enabled, primary video device is integrated GPU etc...
Solution
There seems to be a problem with some boards and also with the new 4a BIOS version. In one case it helped to just flash back version 3, but in another case, that did not help.
The solution was to flash all BIOS versions from the beginning in the right order. You need to download all the files from Gigabyte and just put the BIOS files on a USB stick in order to use the on board flash tool EZ Flash from within the BIOS. Important: Make sure to always chose the "full" upgrade of the BIOS, if given a choice by EZ flash!
So I started with 9 cards connected because I was lazy and did not want to disconnect every card. Flashed F1, then rebooted into OS, shut down. Flash F2b. F2b for some reason did not boot at all with GPUs attached. So I needed to disconnect all cards to have it boot into OS. Shut down. Flash F3. At this point your board should work fine with 12 cards again with the right settings. Do not flash F4a! This will bring back the problem. For science I did. If you do not mess up with a lot of things, flashing back to F3 fixes this again at this point.
Conclusion
Seems that there goes something wrong in the BIOS that gets solved only, if you flash all versions in correct order until V3 (always chose complete flash!). F4a seems to be one cause of the problem. But also boards that do not have F4a installed seem to have this problem, also fixed with the provided solution. At least for boards I had so far.
I hope this helps and I would appreciate feedback! Btw. 300 posts
so I found a possible solution for the said problem.
Problem
Gigabyte Fintech 12 GPU B250 mining mainboard does not boot / post after connecting more than 9 GPUs.
It does not depend on which PCIe slots you use, just disconnecting any card helps, as long as there are no more than 9 connected.
Intro
.. As stated, if the problem solves by disconnecting any of the cards so that there are only 9 connected, you can quickly check if you have that specific problem. There is still a possibility, that your PSU is the problem, especially, if you built a new rig and boot up for the first time. Maybe your rig just draws too much power.
.. It still might be a riser, although you ruled that one nearly out by confirming it is not related to specific GPUs.
.. Might still be a defective component on the board.
Steps done before in no particular order, that were not related to the solution and did not solve the problem
.. Switched RAM and CPU
.. Switched RAM slots
.. Loaded defaults in BIOS
.. Reflashed recent BIOS
.. Flashed old v3 BIOS
.. Checked every setting and deactivated all unneccessary devices
.. Mining mode is enabled, 4G decodeing is enabled, primary video device is integrated GPU etc...
Solution
There seems to be a problem with some boards and also with the new 4a BIOS version. In one case it helped to just flash back version 3, but in another case, that did not help.
The solution was to flash all BIOS versions from the beginning in the right order. You need to download all the files from Gigabyte and just put the BIOS files on a USB stick in order to use the on board flash tool EZ Flash from within the BIOS. Important: Make sure to always chose the "full" upgrade of the BIOS, if given a choice by EZ flash!
So I started with 9 cards connected because I was lazy and did not want to disconnect every card. Flashed F1, then rebooted into OS, shut down. Flash F2b. F2b for some reason did not boot at all with GPUs attached. So I needed to disconnect all cards to have it boot into OS. Shut down. Flash F3. At this point your board should work fine with 12 cards again with the right settings. Do not flash F4a! This will bring back the problem. For science I did. If you do not mess up with a lot of things, flashing back to F3 fixes this again at this point.
Conclusion
Seems that there goes something wrong in the BIOS that gets solved only, if you flash all versions in correct order until V3 (always chose complete flash!). F4a seems to be one cause of the problem. But also boards that do not have F4a installed seem to have this problem, also fixed with the provided solution. At least for boards I had so far.
I hope this helps and I would appreciate feedback! Btw. 300 posts
Purely registered to respond to your post...just in case anybody else is still having those issues.
Firstly, thanks, you are a live saver
Secondly, to confirm, solution of flashing bios 1, 2b and 3 works absolutely fine - board now boots with 11 cards with no issues. Just fyi, when flashing, the full flash option was called "intact".
As for my points:
My rather crude solution, before finding your post, and still being on BIOS 4a, was just to disconnect any cards above 8, boot to BIOS, then go MIT-> Miscellaneous -> and manually set PCIe to x1. Then save and exit, BUT reconnecting any disconnected cards (i.e. inserting risers into mobo) before pressing Enter on "save & exit". That would usually work, and system would then boot fine with 11 GPUs. If that wouldn't work, i would disconnect any above 8, then boot past BIOS, into the boot menu (GRUB), but not yet into system, then plug one riser of the extra cards, soft reboot (ctrl+alt+del), rinse and repeat till all cards were connected, and only then boot into system.
This would however only work as long as the system had power or was only soft restarted. Any shutdown/hard reset would result in boot failing again.
Issue:
Gigashite borked bios 4a. Looks like in that version they have introduced some extra parameter called "CFG Lock", right in the very menu where PCIe speed is (MIT-> Miscellaneous). I have no clue what is that supposed to do, nor could find anything in the manual, but, based on the name, guess its "locks the config". For what purpose I have no clue though. However it seems to be permanently active somehow, no matter the setting, and ALWAYS sets the PCIe speed to x2. Simple math, when CPU has only 16 lanes, and PCIe is set to x2, only 8 cards will work. Anything above will fail. My crude method from above would make the x1 setting persist, in case of soft reboots, but anything else would cause the mobo to default to x2 again.
As for the board failing to boot on 2b and needing all GPUs to be disconnected - bios 3 changelog says "Initial display output default from IGFX" - my guess is they have messed up 2b as well, and it tries to output video from any connected GPU first, before it defaults to iGPU...
I assume, given the lack of any further bioses, Gigashite has abandoned this motherboard, hence if you own it, do not upgrade it past version 3 and you will be golden