real-time performance with SMM and SMI BIOS

I’m currently running into issues with servicing my PCI board IRQ at 0.5ms rate. At random, the IRQ is delayed as if someone has done a interrupt disable, even IRQ 0 is delayed by > 1ms, even if I just monitor IRQ 0 without running anything. My feeling at this point is maybe it is entering “System Management mode” via “System management interrupt” causing this IRQ delay. My question is what is the general approach with such system? How can I disable SMM or is this even possible? I would like to hear from our QNX real-time exports on how they deal with this SMM/SMI mess. By the way, I’m using Advantech PCA-6186-B and PCA-6010 SBC

Thanks in advance.

and yes I have tried diabling all SMI as much as I can from BIOS (usb, power, etc…)

I’ve had one experience with this. SMI could not be disabled. The solution in our case was to find out why it was occuring at all. It turned out that we were in a video mode that was not supported by the video hardware. System management mode was being used to stretch pixels. When we chose a video mode that was supported by the hardware, the problem went away.