WQUXGA a.k.a. OMGWTF – IBM T221 3840×2400 204dpi Monitor – Part 1: Linux

I’m not sure how many people occasionally stop to notice this sort of thing, but to me it frequently seems that technology regresses for long periods from it’s infrequent peaks. In the 60s we saw flights of the likes of XB-70 Valkyrie and the SR-71 Blackbird, and people walked on the moon. Yet in 2011 we are reading about the last flight of the Space Shuttle rather than about the first colony on Mars. It makes a quote from Idiocracy all the more uncanny: “… sadly the world’s greatest minds and resources where focused on conquering hair loss and prolonging erections.

The same pattern seems to apply to some aspects of the computer industry, when cost pressures take precedence over quality, features and innovation. In 2001, we saw the introduction of the IBM T220 monitor, with resolution of 3840×2400 on a 22.2″ panel. It was later superseded by the T221 with very similar specifications, but it was ultimately discontinued in 2005. Nothing matching it has been available since. Today, the screen resolutions seems to be undergoing an erosion. On small panels the “standards” (sub-standards?) have settled at the completely unusable 1024×600, and with total of three exceptions from Dell (3007WFP, 3008WFP), Samsung (305T) and Apple (Cinema HD), the commonly available screens are limited to 1920×1080 resolution. Even 1920×1200 screens are getting more and more rare, especially on laptops, because screens are marketed by diagonal size and for any given diagonal length, 16:9 ratio screens have a smaller surface area than 16:10 ratio screens.

IBM T221 monitors, especially of the latest DG5 variety, are very hard to come by and still expensive if you can ever find one. Typically they sell for double what you can get a Dell 3007WFP for. But you do get more than twice the pixel count and more than twice the pixel density. I have recently acquired a T221 and if your eyes can handle it (and mine can), the experience is quite amazing – once you get it working properly. Getting it working properly, however, can be quite a painful experience if you want to get the most out of it.

My T221 came with a single LFH-60 -> 2x SL-DVI (single link DVI) cable. There are two LFH-60 connectors on the T221, which allows the screen to be run using 4x SL-DVI inputs. This provides a maximum refresh of 48Hz. There is also a way to run this monitor using 2xDL-DVI inputs at 48Hz, but this requires special adapters, but that is a subject for another article, since I haven’t got any of those yet.

Using a single LFH-60 -> 2x SL-DVI cable, there are only two modes in which the T221 can be run:

1) As a single 3840×2400 panel @ 13Hz using a single SL-DVI port

2) As two separate monitors, each being 1920×2400 @ 20Hz, using two SL-DVI ports

The 13Hz mode is completely straightforward to get working on both RHEL6 and XP x64, but 13Hz is  just not fast enough. You can actually see the mouse pointer skipping as you move it, and playing back a video also results in visible frame skipping. So I have spent the effort to get the 2x1920x2400@20Hz mode working on my ATI HD4870X2. The end results are worth it, but the process isn’t entirely straightforward. The important thing to consider is that when running in anything other than 3840×2400@13Hz mode appears to the computer as two completely separate 1920×2400 monitors.

IBM T221 with Linux

ATI‘s Linux drivers aren’t really mature enough for the job, and to achieve the best results, you have to use aticonfig to generate xorg.conf without xinerama support, start X-Windows, fire up the amdcccle configuration utility for ATI cards, enable dual screens, then add xinerama support. If all this sounds complicated to you – it is, and it took a lot of trial and error to get right. So to save you the effort, here is a copy of my xorg.conf file. This is from a RHEL6 machine using the ATI fglrx driver. It will almost certainly work on other distributions, too, with little or no modification.

This still won’t work quite as you’d hope, though – xinerama passes information to the applications about the geometry of the desktop, and apps will only maximize to one screen. This also goes for the task bar, and applies to video playback. The last bit of magic involves faking the xinerama information. Nvidia drivers come with a built in option for this: “NoTwinViewXineramaInfo”. Unfortunately, ATI drivers have no such option. But, this being the world of Linux, there is a backup plan. There is a LD_PRELOAD library called Fake Xinerama that can be used to override the screen geometry passed to applications, and make the applications think they are on a single 3840×2400 screen. All you need to do is the following:

1) Compile fake xinerama from the like above
2) Add the line “/usr/local/lib64/libXinerama.so” to your /etc/ld.so.preload file.
3) Create a file ~/.fakexinerama containing:

0 0 3840 2400

The first line contains the number of screens, the second line’s format is:
<origin X> <origin Y> <width X> <width Y>
If you are booting into graphical environment immediately (runlevel 5), you will need the .fakexinerama file in root’s home directory, too, since gdm/kdm run as root.

And if you have managed to follow all that, you will have a single seamless  3840×2400@20Hz desktop.

2 thoughts on “WQUXGA a.k.a. OMGWTF – IBM T221 3840×2400 204dpi Monitor – Part 1: Linux

    • As far as I am aware, you can only get them with the monitor, and only if you buy it from this ebay shop:


      They are not available separately.

      Personally, I find 3840×2400@20Hz to be perfectly acceptable even for gaming, just make sure you have vsync enabled. But if you haven’t got the monitor already, it’s certainly worth getting one with the adapter from the shop linked above.

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