I can set it manually, but what if it doesn't post? Server is in dc, and I am not sure if I can enter bios with ipmi if server will not post?
Ok, sorry for spam, but, YEY, it works, I set it to 1066mhz manually and server posted and what is more interesting, it raised voltage to 1.5v
Now I'm curious ... How did you make that change? If not IPMI?
Yes , but I will probably can NOT change bios right?
Are you asking if you can change BIOS settings via IPMI? If so you absolutely can. If you didn't make the changes you referenced (forced memory speed/voltage) via IPMI, you did so via physical access? Previously you noted the server was in a different location, so I'm confused here (but I'm physically tired, and especially tired of shucking drives, so I may have missed the obvious - see final note below).
Reference Figure 1 - BIOS settings via IPMI View client - an example from the SMCI IPMI View Client, KVM console (emulation of exactly what a connected monitor would present).
What
@SPCRich is trying to convey to you is that even if "Chassis Power Status = OFF" (i.e. "lights out"), IPMI operates independently of the system's BIOS / OS, etc.
Reference Figure 2 - System Summary via IPMI web ui - an example showing that you can still manipulate settings while the chassis is in an OFF state, in that specific screenshot Power On. However, a good many of the server's settings are configurable via IPMI, with the chassis OFF, more so than even if you had a keyboard / monitor directly connected in a dc.
Regarding IPMI & POST, if you encounter an error IPMI still presents the boot screen and notes "System initializing ... [EC]"; where EC = a two character alphanumeric code such as BA, B7, B9, etc. in the Java Viewer ...
[If you know all of this may bad, but I got a message notification while I happened to be in my BIOS via IPMI and figured I'd screen shot it for you - as it seems like you are looking for a better understanding here and everyone is happy to help]
Figure 1
Figure 2