1920x1080 HiDPI on mid 2010 27" iMac

[Silversil]

Hi everybody.
I have this iMac:
- 27" Mid 2010
- 2,93 Ghz Core i-7
- ATI Radeon HD 5750 1024 MB.

Native resolution of my monitor is 2560x1440 but it's too small for me.
Actually, 1920x1080 it's the perfect resolution for my eyes but it's too blurry; so I tried to use SwitcResX (4.6.6 free demo) to improve a 1920x1080 HiDPI (putting on the custom resolution panel a 3840x2160 resolution); then I saved and reboot my Mac but the 1920x1080 HiDPI resolution doesn't appear and in the SwitchRes panel is written "Not Installed".
The maximum HiDPI resolution that I can have it's 1280x720 but it's too big!
So i emailed Stephane Madrau and his answer was:

<If "Not installed" is coming, it means that SwitchResX cannot save the resolution on the System files. That occurs when it's not able to write the file, perhaps because SIP is not disabled; or when it doesn't save the files any more, because it is not registered and it is not in trial mode any more.>

Actually, before trying i disabled SIP, anyway I tried to purchase SwitchRes full version (licensed) and I tried again to custom 3840x2160...now SwitchRes said me "need reboot"... So I saved, tried to reboot but nothing.. 3840x2160 (and scaled 1920x1080 HiDPI) is not showing. Then, I tried to open SwitchRes panel but now is written " Not activeted".

So...I was thinking maybe there's some problem with my GPU, my O.S. or maybe my iMac model...
Can anyone help me???
I'm going mad...

Thanks a lot...bye guys.

 

[chrfr]

Native resolution of my monitor is 2560x1440 but it's too small for me.
Actually, 1920x1080 it's the perfect resolution for my eyes but it's too blurry; so I tried to use SwitcResX (4.6.6 free demo) to improve a 1920x1080 HiDPI (putting on the custom resolution panel a 3840x2160 resolution); then I saved and reboot my Mac but the 1920x1080 HiDPI resolution doesn't appear and in the SwitchRes panel is written "Not Installed".
The maximum HiDPI resolution that I can have it's 1280x720 but it's too big!

You aren't going to be able to do what you're trying to do; it's a hardware constraint. You'd need a 4k display (3840x2160 pixels) to have 1920x1080 HiDPI. Like you saw, your only option is going to be 1280x720.

 

[Silversil]

Thank you for your quickly reply but SwitchRes is made just to apply above not-native resolution on iMac...I mean just to simulate Retina resolution. Other users made this thing, successfully. So I dn't inderstand what's going wrong.

 

[chrfr]

Thank you for your quickly reply but SwitchRes is made just to apply above not-native resolution on iMac...I mean just to simulate Retina resolution. Other users made this thing, successfully. So I dn't inderstand what's going wrong.

This thread from a few years ago has some information from the developer who indicates that this only works with Nvidia graphics, not AMD like yours has. https://forums.macrumors.com/thread...de-on-macs-fixed-mouse-delay-problem.1568657/
Maybe that's changed by now.

 

[Silversil]

Mmmhh....probably you'right. This is the focus of the problem. So... you know if I could, if it's possible, change my AMD into a Nvidia? I really need that resolution!

 

[Silversil]

Or maybe I could downgrade to Maveriks, becauase I read somewhere that this O S. is the last that let you set an above non native-resolution. From Yosemite, everything change. Could be a good option by you (I'm not interested about new functions of lasts O.S.)?