Custom Resolution Utility (CRU)

[Roshi]

Hello, new here.
I have a Samsung S24E390HL monitor, and ATI Radeon HD 4670. It is connected through HDMI.

I cannot set a custom resolution of 1920 with 1080 at 75Hz, it does not appear in monitor refresh rates after I restart.

I placed it in the customs resolutions, with LCD Standard, or Native, or in the standard resolutions, or I clicked edit on the extension block, and added it there, it does not work. I imported the hdmi.dat file, and added it there in the extension block, the monitor gives an error message and I need to restart in safe mode to reset.

There is a video here showing my exact monitor, using CRU 1.0, unchecking "enable extension block", but it did not work for me, my monitor refresh rates after the restart show the only choice is 60Hz, the other choices are gone:
https://www.youtube.com/watch?v=e3U_kRt3y_o

Also this review says the monitor can be overclocked at 75Hz, using CRU and HDMI:
https://pcmonitors.info/reviews/samsung-s24e390hl/

What am I doing wrong? I tried with or without the monitor driver. Is it something from ATI Catalyst? The pixel format, or another setting?

The thing is - I did succeed in overclocking it at 70Hz - and I cannot remember what I did with what settings, then I tried for 75 Hz and reset it, and it does not work in any way, 70 or 75, the refresh rate does not appear after restart.