Now i have done some testing - motherboard works just fine, everything works and is stable without -5V.
But i saw some trouble with sound cars, i dont know yet if it is related to this missing -5V rail.
I tried couple cheap Crystal CX4237B chipset based card and ExpertColor Yamaha YMF718-S. Both had soundfx issue in Doom and Wolf3d, lots of loud hissing and cracking involved. Wolfenstein was at some point even playable, but i noticed that opening/closing door soundfx triggered almost always this awful noise problem.
Older games, that i tried, worked just fine.
Will do some more testing with differend soundcards and PSU with -5V rail.