Forced convert to Linux Mint on a high dpi iMac

[fox]

I have been looking for the right driver; my card is the Radeon R9 M395 (not 390 and not 395X). One site suggests that the right driver is the AMDGPU-PRO Driver, but this is built for Ubuntu 16.04 LTS and not 17.10. It isn't clear to me that there is an appropriate Radeon proprietary driver (or open source) for my card, for any Ubuntu newer than 16.04.

[Jason]

That would probably explain why Linux Mint 8.2 works then, having been based on 16.04. Did 16.04 support Flatpaks? I suppose if you really prefer Ubuntu you could install 16.04 and flatpak anywhere you need a newer version of an app. My guess is that it's actually tied to the kernel release series in Ubuntu 16.04 (4.4 series, I think).

[fox]

I didn't try installing 16.04, but I did try running it from a live usb. It required either nomodeset or nointremap to boot up (I think the former), and when it did boot up, I had no control of resolution or screen magnification. Perhaps if I installed it and then installed the AMDGPU-PRO driver, I would get it back. I might try that when I have more time. But in the interim, the reason why Mint, based on 16.04, works and Ubuntu and other Ubuntu derivatives don't, remains a mystery to me.

Going back to that AMDGPU-PRO driver, it might work on 17.10 as well, but it was meant for the LTA release. I could try that by attempting an installation on the big hard drive inside the iMac, leaving the SSD with Mint on it alone.

[fox]

I've done a few more tests with Ubuntu. Ubuntu 16.04 was easily started up with nomodeset, and easily installed. It booted up pretty quickly either in rescue mode, or faster if starting up with noapic nomodeset. The latter has to be there if you want it starting up quickly. Nointremap in place of nomodeset doesn't cut it (unlike Mint). The installed version doesn't show resolution options other than 3840x2160, but it does allow you to use settings to magnify window text and regular text. I found that I could use these to generate good settings, but I wanted to try more. The more was to install the amdgpu-pro driver. I could download and install it, and once I was able to boot it all the way. It resulted in smoother window movement, though no better than what I get on Mint. With this driver installed, settings now showed alternative lower resolutions, including the 2560x1440 that works well in Mint. So I tried that. Result: I could boot to the login window but no further. Putting in my password just brought back the same window. So I started over again, thinking I would see if this driver worked without messing with resolutions. Unfortunately, I forgot to follow one other instruction, which was to put me into the Video group. Now I can't go any further than the startup screen.

I'm going to try rescue mode, drop to a terminal and put me into the Video group, just to see if the driver works if I don't mess with resolution. I'm also going to try two other Ubuntu-based distros, Zorin and Ubuntu Budgie. It's still a mystery as to why Mint works without all this messing around and Ubuntu doesn't. One thing I did notice with Mint is that the command

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lspci -k | grep -EA2 'VGA|3D'
shows that the amdgpu driver is being used. Not sure about Ubuntu.

Tried Zorin. It boots OK with nomodeset. Window movement appears to be more fluid than that of Ubuntu, but I'm not sure. In any case, no alternative resolutions show in settings, and there are none of the magnification settings that I can find in Ubuntu Unity. So not helpful.

Tried openSUSE, an education edition because vanilla openSUSE only gives an installer, not a live USB. I can't remember whether it required nomodeset or not, but it booted reasonably quickly to a KDE desktop. KDE seemed to have few options for scaling and the window movement wasn't fluid. Not worth looking further.

Went back to Ubuntu 17.10 and installed it. Works OK with nomodeset and scaling of fonts. Window movement OK but not so fluid. Installed Unity into 17.10. Windows move better and scaling is very good, but something went wrong and themes and icons went back to default. At any rate, 17.10 gnome is usable and I´ll play around with it another time. I´ll probably put 16.04 on it as well and see which works better (this time without the Radeon driver). They´re only there as backup because Mint works the best on this computer, despite the fact that the same driver is installed (amdgpu).

So I leave this set of tests with the following conclusions:

Conclusions:
- Installing a propietary Radeon driver appears to be a non-starter with my video card, at least until AMD puts out some updates
- No distro allows for the 5K resolution that this Mac is capable of
- Of all the distros I tried, only Mint (cinnamon) gives me the option to use a resolution other than 3840x2160
- The 2560x1440 resolution available on Mint, combined with scaling provides the best desktop experience I could get in Linux
- Desktop environment matters a lot on this iMac. The best DE for it seems to be Cinnamon, followed by Unity. (I haven't tried xfce or mate.)
- Mint (Cinnamon) provides the smoothest window movement options on this iMac. Next best is Ubuntu Unity.

[fox]

OK, big breakthrough! I can now run the proprietary AMD driver (amdgpu-pro) on Ubuntu 16.04. The previous problem was that the non-amd intel video driver for the onboard video was interfering with the proprietary driver at startup. I found a posting that dealt with this, and it suggested a different install command:

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./amdgpu-pro-install --px

... the --px replaced -y

That did it. Window movement is now much smoother than before, though not noticeably better than that of Mint. But I´m running Ubuntu on the HD, not the SSD like Mint, and I´m running it at higher resolution. Now I´ll have to decide whether it is worth replacing Mint with Ubuntu on the SSD. Whether I do or don´t, this is very significant. I now know that my Late 2015 iMac can run Ubuntu smoothly with high resolution. One other thing I want to try is to see if 17.10 will run with the amdgpu-pro driver.

One other neat thing about installing the amd driver in 16.04 - no need to put any special commands into the grub menu to get it to boot. So neither ¨nomodeset¨ or ¨nointremap¨ is needed.

[Jason]

Nice! Can you run it at native resolution now?

[fox]

Nice! Can you run it at native resolution now?

Nope, 3840x2160 is still the max. The MacOS apparently does something unique to give 5K resolution on an iMac. You can run Windows on this Mac, and you'll get the same maximum resolution that Linux can give you. I don't know if that issue can or will ever be addressed. This was never a big deal to me. 2560x 1440 is plenty good on a 27" monitor. Even with 3840x2160 on Ubuntu and scaling, not all apps take that scaling. One that doesn't is Mendeley, a cross-platform reference manager that I use extensively. On Mint with the resolution set at 2560x1440, it is quite readable. On Ubuntu with the higher resolution, I have to wear my glasses to read it. So in the end, there may be minimal benefit to running Ubuntu with the proprietary driver vs running Mint without it.

I'm going to do more experiments to find out if I'm better off with Ubuntu, including using the proprietary driver at 2560x1440 resolution. But even if I end up sticking with Mint, the experiments are important to me. When I started with this iMac, Mint was the only distro that would boot in a reasonable period and run properly. That worried me, but now I know that this is no longer the case. Now if I can only figure out how to boot Clonezilla on this computer!

[Jason]

Cool. I think that even 4K is too high a resolution for that screen size. Seems overkill. At 40" sure, but 27" seems too small a screen for that resolution to use efficiently by most.

[fox]

That's what I would have thought before I got my first 27" iMac, an old one that was given to me by a colleague who upgraded. 2560x1440 is beautiful on a 27" display, and the difference was noticeably better than the 1900x1080 I got on a 27" HP monitor. I do agree though, that the higher resolution on the Late 2015 iMac doesn't make any difference to me. Next time you're in Staples, take a look at one of these hi-res iMac monitors. I'm sure you'll see the difference, vs a 1080p 27" monitor in the same store.

[Jason]

I wasn't talking about 2560x1440; I was specifically talking about 4K on 27".

I agree that 2560 x 1440 would be fine on 27". The pixel density is probably about the same as 1920x1080 on 20-22" so text and icons, for example, should appear at about the same size - the desktop will just be roomier.

[fox]

Well I just learned something. I always thought 4K was 2560x1440, but I see now that this is referred to as either QHD or WQHD. Looks like I either misread the 27" iMac ads or made the mistake by reading a recent 21.5" iMac ad. So I now agree with you; 4K has no obvious advantage over QHD on a 27" monitor. Thanks for pointing that out.

[fox]

I ran a final set of tests. One of my big concerns was that Clonezilla wouldn't boot. I found a posting on the internet that suggested that sometimes the Debian version would work where the Ubuntu version wouldn't. The version that wouldn't boot was the Ubuntu-based alternative stable. The Debian stable version (2.5.2.31) did in fact boot! I also tried the most recent Ubuntu-based testing version (20171101-artful); my iMac didn't even see it.

Finally, I tried installing the amdgpu-pro drivers on Ubuntu 17.10. Didn't work; there was even an error during installation. I tried booting with it anyway and it wouldn't boot regardless of grub parameter. I was able to boot into rescue mode and uninstall the drivers. So I still have 17.10 to play with, should AMD issue an update. (They probably won't until the next Ubuntu LTS.)

What I haven't tried is installing the driver on Mint 18.2. Window movement is already OK on it, and the only thing not working to Ubuntu standard on it are the Microsoft Office 2010 programs on Wine (via Crossover). For some reason, their boot time varies wildly from almost immediate to ~15 sec, and I don't know why. (I never had this problem on Ubuntu.) While annoying when in long boot, it isn't a show stopper. Now I'll just have to decide whether to use Mint 18.2 or Ubuntu 16.04 as my default.

[Jason]

Well I just learned something. I always thought 4K was 2560x1440, but I see now that this is referred to as either QHD or WQHD. Looks like I either misread the 27" iMac ads or made the mistake by reading a recent 21.5" iMac ad. So I now agree with you; 4K has no obvious advantage over QHD on a 27" monitor. Thanks for pointing that out.

No problem. 4K refers to the number of horizontal pixels being around 4,000.

[fox]

What I haven't tried is installing the driver on Mint 18.2. Window movement is already OK on it, and the only thing not working to Ubuntu standard on it are the Microsoft Office 2010 programs on Wine (via Crossover). For some reason, their boot time varies wildly from almost immediate to ~15 sec, and I don't know why. (I never had this problem on Ubuntu.)

I think I have finally figured that out. I had two wine-type installations of MS Office 2010 running on Mint; one in Crossover and the other in PlayonLinux. I eliminated the later after it got confusing as to which one would start. But the system didn't eliminate it as the default app for starting up an Office file. Clicking on that default must have caused a delay as the system looked for that program in the POL virtual drive. When I changed the default opening program to the Crossover version, Office files now open up instantly.

At this point there are no remaining problems with my Mint 18.2 installation, and windowing is actually smoother than on Ubuntu 16.04, even with the latter using the amdgpu-pro driver. I'm going to keep both on my drive, but it looks like I am now a Linux Mint convert (at least on this computer). If I have no reason to switch after a few months, I'm going to have to think about donating to Mint for giving me such a great experience on this non-Linux-friendly iMac. 

[Jason]

Cool. I think it's good when we give a little back to the community like that, too. I donated quite a while ago to the Ubuntu MATE guys back when I was using it regularly. Probably do so soon for the LM guys, too.