Asus CPU Support list for your motherboard doesn't show your processor as being supported.
The FM2+ Motherboards are mainly considered to be End of Line or Legacy with no more driver or BIOS updates. So if your motherboard doesn't show your A8 7680 being supported by now you won't find a BIOS for it.
PCPARTPICKER has a list of all compatible A8 7680 Motherboards which means they have the correct BIOS version to support it. But another Motherboard BIOS will not work on your Motherboard unless it is the same model: https://pcpartpicker.com/products/motherboard/?compatible_with=Y8VD4D
According to the PCPARTPICKER list Asus A68HM-K CPU SUPPORT LIst does show supporting A8 7680 with a BIOS version. But that BIOS may not work in your A68HM-E motherboard.
NOTE: Not sure how accurate the above link motherboard list is.
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