After clr cmos black screen

Model Name : GA-H61M-S1(rev. 2.0)
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M/B Rev : 2.0
BIOS Ver : F2
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CPU Brand : Intel Model : Celeron G530 Speed : 2.4 GHz
Operation System : Win 7 64-bit SP : 1
Memory Brand : Kingmax Type : DDRIII
Memory Size : 2x2 GB Speed : 1333 MHz
Power Supply : 400 W

no graphics card
I use the integrated on the MB.

I wrote a letter to gigabyte tech support but until I get the response I would be interested in your opinion about my issue.

I was making a BIOS upgrade (which I know is not recommended) with @BIOS because I couldn't access the BIOS (delete) all I got was a black screen and then the system stopped loading.
After I finished the BIOS upgrade nothing has happened still couldn't get in the BIOS. Then I decided clr cmos to get back factory defaults. So I removed the battery for 5 minutes with computer unplugged and power button pressed for removing residual energy in the circuits. And since then when I turn on the computer I get one short beep and black screen. (power led on, hdd led not flashing).
I would welcome any suggestions regarding this issue. I know that this MB has backup bios. I assume the main bios is gone so I would appreciate any methods how to force the backup bios to kick in.