Successfully flashed back my old bios and found its p/n. It is 113-PC2050-54. After that found it in 'ATI bios collection' and compared it with my one - they are 100% identical.
Now I am sure that my videocard has valid bios.
P.S. The bios found in 'ATI bios collection' has reference to ATI manufacturer and Hynix 3.6 ns memory but my videocard is made by Sapphire and memory by Samsung. Is it useful to upload it (bios)?
P.P.S. Thank you guys for your quick help.