I think it depends on the system your running the card on. Based on the lockups and your on a newer supply the 5V rail amperage is too low.
I recently switched my systems (socket 7 and socket A) to use Enermax supplies from the era. But just with a guess im thinking something around 350 watt with 20 amps on the 5V would be more than enough.

Heres of my enermax's (its more than enough):
https://www.newegg.com/enermax-noisetaker-eg4 … N82E16817103459

I pretty much only use newer Seasonic PSUs.

Go up high enough and you have a plenty large enough 5v rail.

Also remember that older power supplies are most likely, at the minimum, going to need the capacitors replaced or the power coming out of them is going to be really dirty and also likely to barely be in spec if in spec at all.

Also, older PSUs are, for the most part, utter trash in regards to the efficiency and power ripple. The brand and ld as doesn't really matter. The OEM that actually made the PSU is what matters and really any power supply used should have high marks given from a PSU reviewer such as JohnnyGuru.

[H]ardOCP used to do real PSU testing as well but all those reviews are offline as the whole site was mothballed except for the forums.

Check overscan settings in Catalyst Control Center. Alternatively - try to adjust refresh of your resolution via power strip (or other software for monitor manipulation).

Thank you all for your comments. At the end I ended up buying an Acteck power supply. It is... well, lets just say that is a brand which has been making power supplys since long ago but they are in the low end. However, they do provide the advertised 30 amps in the 5v rail. The sudden resets finally stopped and I have been playing lately in long sessions with it. Also, at the end I switched to another monitor and used the VGA to obtain 1080p output and also other resolutions without going "out of range" in my 4k monitor. The 4k monitor apparently really only likes newer hardware to work... so I went VGA and all is good now.