PCIe lanes, usb 3 controller cards, IRQ - troubleshooting



  • @Propagandalf if the motherboard has a on board gpu, remove the extra GPU to draw less power or else use a less power hungry GPU card if you have one available. If either works then you know for sure its a power issue.



  • @iKnow0 I don't have either of those alternatives, unfortunately.

    Edit: I think the rx470 uses about 130W during heavy load, which isn't all that bad.



  • @Propagandalf borrow a more powerful psu or old GPU, most gamers will have both spare.



  • @Propagandalf you could also work it out using math and the specifications for each device.



  • @iKnow0
    I could do that of course, but this system was built by professionals at a local IT shop, so I find it strange if the PSU is not powerful enough.

    I did a rough calculation a few weeks ago and came to the conclusion that I'm using quite a bit less than what the PSU supports.



  • @Propagandalf do you have any other psu's?



  • @iKnow0 Not currently, but I might be able to get hold of one in a few days.



  • @iKnow0
    OK, so I got hold of a 750W PSU, but when I replaced it, I can't even turn the machine on, there's no action whatsoever unlike before. The PSU worked on my friend's computer, so not sure what is going on.

    I re-used the cables from the old PSU on the new PSU to save time and fiddling about, was this maybe a bad idea? Are cables universal between different makes of PSUs? If this is the issue I will try again tomorrow with the "correct" cables, but I have run out of time for tonight.



  • @Propagandalf double check all cables are secure



  • Your problem is not the PSU, you POST fine with 2 cards but not with 3, the 3rd card pulls milliamps at best. You have an interrupt problem, hence your code 96

    Go into BIOS, make sure Graphics adapter is set to PCIe, make sure to disable onboard graphics, disable whatever you can that you are not using such as legacy USB, lpt or com ports, etc...



  • I think @Focus is right about the PSU, but for what it's worth, cables are not always compatible between different PSUs, even if they have the same connectors. Be careful, don't fry your motherboard or components!



  • @zyzzyva said in PCIe lanes, usb 3 controller cards - troubleshooting:

    I think @Focus is right about the PSU, but for what it's worth, cables are not always compatible between different PSUs, even if they have the same connectors. Be careful, don't fry your motherboard or components!

    Especially with a board like that $700 ouch



  • Thanks for the answers. I have tried 3 controller cards on another system (B), and it works fine. That rules out any general incompatibility issues on the producer's side when using more than 2 cards.

    I decided not to test with original cables and fire up the 750W PSU on the original system (A), as it would mean ruining the existing cable management inside the case. Instead, I ran a PSU calculator based on all the components I use, and it tells me that I will draw 371W and I have a 650W PSU from before, so power should definitely not be an issue when installing these cards that draw very little additional power.

    I am a bit scared to reconnect the original PSU on system A now, in case I destroyed any components yesterday when I used the unoriginal cables! The question remains: Why do 3 cards work on system B, when system A won't get through POST with 3? I will try to figure out how I can disable stuff I don't need in Bios as the next step in my troubleshooting, like @Focus suggested.

    Update 1:
    System A was not damaged yesterday!

    Update 2: I disabled several items in BIOS, and now I am able to get 3 cards working on system A! Fourth card gets same error, so I will try to disable more stuff if I can, just need to make sure I don't disable anything vital.



  • I have now disabled just about everything I can disable, and I have installed the producer's drivers instead of the generic Windows drivers, but to no avail. I tried swapping slots again too. I'm still learning about IRQ, but I suspect that I somehow need to find out which channels are free, and also somehow manually assign free channels to controller card number 4 and 5. This is no easy task, and my BIOS apparently does not have any settings for this. To me it seems strange why there are such limitations, but what do I know.



  • @Propagandalf glad to see you are making some progress. To see what IRQ devices are using
    right+click my computer-> Manage -> Device Manager
    Then from the view menu choose "Resources by connection"
    There you will see a tree view for IRQ which shows the IRQ info.

    p.s. Also check that you have the most up to date BIOS on the motherboard, this can be checked on the manufactures web site.



  • @iKnow0
    Thanks! I already have the latest BIOS, and found out how to view IRQ channels. But, the option to turn off automatic assignment is grayed out (in device manager), and I can't find a way to change that in BIOS. But, I noticed that if the device is disconnected or has been connected at some point, it creates a "trace" in device manager when I press View - Resources by type - Interrupt request (IRQ). There, I am able to change the assigned resources of disconnected devices it seems.

    I will fiddle about with this a bit, and I will also try to disable a device that is connected, to see if that enables me to change any allocated resources through IRQ.

    Edit: In BIOS there may be an option called "reset configuration data", which might force the system to 'forget' IRQ assignments and reassign them, which may result in positive news as I suspect I have enough free channels that are not being allocated properly.



  • I feel like I have exhausted all my options now, and I still can't get more than 3 cards to work. I freed up loads of on-board devices after being able to use three, so you would think that there are enough vacant IRQ channels to solve the issue if that was the only problem. As I understand it the PCI bus controls the sharing of IRQ channels, so maybe there's something with that. I have a feeling that I either need to be able to set IRQ/bus manually (which I don't think is possible on most modern machines), or reset the automatically handled IRQ/bus resource allocation.



  • Does anyone know if creating a virtual machine (VM) can solve this problem somehow? I'm not too familiar with VMs, but if they function like a physical system even though they are virtual, then maybe I could let a VM "take over" some of the PCIe USB 3 controller cards, so that they will not conflict with POST and boot on my physical machine? I'm thinking out loud here, hoping someone else knows more about it than I do.



  • @Propagandalf said in PCIe lanes, usb 3 controller cards, IRQ - troubleshooting:

    Does anyone know if creating a virtual machine (VM) can solve this problem somehow? I'm not too familiar with VMs, but if they function like a physical system even though they are virtual, then maybe I could let a VM "take over" some of the PCIe USB 3 controller cards, so that they will not conflict with POST and boot on my physical machine? I'm thinking out loud here, hoping someone else knows more about it than I do.

    Will not work. Your IRQ problem is on a hardware level and not software.



  • @Propagandalf if you have an os installed on the pc, setup VNC (remote control) on it. Then you can disable the mouse and keyboard in the bios giving you 2 extra IRQ's. You will need another pc or laptop to connect to it to control it.


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