Question hd 7950 displays vertical lines and blocks bios from loading

Aug 28, 2021
around 2 days ago i was playing apex. suddenly the pc froze and the screen displayed a pattern similar to tv static. after trying to boot it it sometimes shows: operating system not found. remove drives with no os. press ctrl+alt+delete to restart (or something along those lines)
and after i restart it for some reason it shows the loading bar from windows xp. also drivers dont work. i can open windows without drivers, still with vertical lines on screen. as soon as the drivers are almost completed the screen turns black and then turns off completely.
i got the card second hand. the card had 1x8pin and 1x6pin. i did not have the proper cables from my psu so i had to cut the psu end from the 8 pin and solder a header which fit. for the 6 pin i used a sata to 6 pin adapter. the card worked fine for some days, untill this happened. what could it be ?
Are you seriously asking what's wrong with it?

You are literally saying that you went Macgyver with the PSU and you are surprised with the outcome?

For starters, if a PSU does not have the proper connections for a GPU, then it's NOT meant to power said GPU. You most probably damaged the GPU and possibly other hardware.