At a mod's suggestion I'm moving this question here from my separate thread:
After installation of El Capitan, I got to the part where the gui was supposed to start, but instead I got a spinning circle on a black screen, a second of the mouse in the upper corner, then the spinning circle again. I booted into safe mode and the system was at the proper resolution, but every time I scrolled or clicked it redrew instead of moving smoothly. I couldn't find any other answers to my problem and decided to try the NVIDIA Web drivers for 10.11.3. After reboot I was able to reach the login screen with a normal login, but the NVIDIA driver thinks my ASUS PB278Q monitor is a TV and restricts it to 1080p. Under Yosemite it was correctly detected as 2560x1440, but in El Cap it's 1080p stretched to fit the screen (overscan was on by default).
I've tried multiple things to fix the graphics problem, but I'm back to using NVIDIA web drivers and 1080p resolution. If I boot to safe mode I get 2560x1440, but not in normal mode. Some of the things I tried that didn't help:
1) Switching to OS X Default Graphics Driver - when I reboot I get back to where I was. From the text size it seems to be trying to show the login screen at 2560x1440, but it keeps showing me the text of mounting the Time Machine partition (in a verbose boot), then going black with the mouse, then back to the Time Machine partition lines. If I boot normally it will either fail completely with the circle/slash symbol or get to the GUI part and go back and forth between the spinning circle and the black screen with the mouse. I left it there for 2 hours and it was still cycling. The only way I was able to get out was to boot to safe mode and reinstall the NVIDIA Web drivers, bringing me right back to 1080p.
2) Changing SMBIOS from 3,1 to 14,2. No effect.
3) Upgrading to 10.11.4, which also entailed finding the beta NVIDIA drivers in this post:
OS X 10.11.4 Update. I also had to change from OsxAptioFixDrv-64.efi to OsxAptioFix2Drv-64.efi. No change from what I reported above. NVIDIA works at the wrong resolution, no NVIDIA results in an endless loop.
I've read this thread, and here's what else I have to say:
According to the chart linked from this post, my 0x0fc8 card should work with or without NVIDIA drivers, with injection off. I just went through the combinations anyway to see if anything helped, and nothing did. With no injection and OS X drivers, OS X thinks it's a 1280x1024 projector, and the screen redraws instead of scrolling. With OS X and injection, it reboots. With NVIDIA web drivers and injection, it reboots. With web drivers and no injection, my monitor is detected as a 1080p TV and it seems to look fine except the resolution is wrong (ie, the screen actually scrolls when I scroll instead of visibly redrawing).
In safe mode, the display is detected at the proper 2560x1440 resolution, but as I mentioned the screen redraws when I scroll and move around. I wish I knew the proper term for that, but that's how it looks. I'm trying everything I can to find the proper combination that allows 2560x1440 and a normal boot. The fact that it detects it fine in safe mode means something is loaded in normal mode that makes the computer think my monitor is a TV. I wish I could figure out what...
If you've already gotten past this, maybe this will serve to help others who stumble on this.
