you should’ve been more prepared when flashing a GPU and make sure you have backups because it can be extremely risky when flashing cards cause Isn’t like a motherboard where you can find the exact bios for your board and flash it back from a USB stick. In your case it’s very lucky it still functions cause most times it would be bricked making it usless.
Almost every day there are new threads regarding bricked graphics cards due to wrong BIOS flashing, and since eidairaman1 is no longer around to help, here is a guide how to deal with a bad VGA BIOS flash. Find the correct BIOS First off, you'll have to find a copy of the original BIOS. In case...
www.techpowerup.com
you did mention techpowerup so I’m assuming you went through this article, you just need to try your best to work it out yourself. Try finding the right and it has to be the exact bios within the card inspect it carefully and take it slow.
I’ve did see a video where this guy had this flash tool for his card although it was meant for those scam gpus that were suppose to be gtx 750 ti’s but instead it was a GTS 450, but the process might be a bit similar to this since he’s pretty much flashing the card back to its original bios.
View: https://m.youtube.com/watch?v=Ra0T0j5KoAc
flashing a GPU back to its original bios isn’t very easy and it requires a lot of experience and patience, you should’ve used an old card, or buy a cheap card to flash it for practice before using it on your main card.
I’m guessing you wanted to flash yours for better overlooking and better stability so pretty much able to to bypass the cards locked Voltage core.