Ok, it means, I need to use microcode
for LGA775 otherwise it will not work, please correct me ?
I can't honestly say. I talked to an expert about this yesterday and pointed out that early sandybridge required the microcode update to work at all, later ones did not.
It's quite likely that if you have a new stepping of an end of life chipset you'll be fine. It's hard to say.
For my machines, I always enable microcode upgrades because debugging issues with bad microcode is really not fun at all.
ron