SMC 4028GR-TR + Newer NVIDIA GPU's; still looking for symptoms caused by this issue.

Step-by-step guide

Remove all PCI-e components from mid-plane, just to be safe
Flash motherboard BIOS to newest (310 as of this article's creation; meaning released 3/10, year not mentioned but you can look at date details within BIOS... 2.0a revision?); reboot
Once booted back into DOS, CD into folder containing the BIOS version you just flashed; type 'update' and when prompted for number, do one at a time (1-4)
After 4, just reboot system again
Once booted back into DOS again, flash back the BIOS to the mfg. initial version (727; 7/27 of last yr, should be 2.0 revision, check date in BIOS)

Engineers report that an earlier version needs to be flashed depending on CPU being used.

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