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If anything has marred the Mac mini’s image, it is the ‘dim video’ problem. Some users with VGA monitors have reported that the video display is dark, and that whites cannot be achieved. The problem does not affect monitors connected directly using DVI. Reports are of varying magnitude—from no problem to unusable, and sites such as Macintouch and XLR8YourMac offer extensive user accounts on the problem. These reports vary in symptioms, severity and resolution, indicating that there may actually be several issues at play. To lump everything under ‘dim video’ is perhaps unfair, but that does seem to be the predominant issue.

We tested our modmini test machines (each purchased over a range of several months) with over a dozen different LCD and CRT monitors. We didn’t detect a problem at first (as discussed in our KVM article), but it showed itself upon testing with a monitor that accepted dual inputs.

As it happened, a Power Mac G4 (“Quicksilver”) was connected to the display’s other input. Switching between the G4 and the mini, the mini was obviously darker than the G4. From that point forward, the problem was immediately noticeable on all monitors we tested. We therefore suspect that those who do not notice a problem may simply lack an appropriate point of reference, or they have a monitor which doesn’t exhibit the problem. (Apple’s past VGA monitors, for instance, consistently display a bright image in our testing.) With these observations, we examine why the problem seems intermittent across users, and we provide a mostly-complete guide to addressing the problem.

Analysis

It appears that the mini puts out a VGA signal that is not as strong as (or differently balanced than) most desktop hardware. We’re not in a position to address whether it is in spec or not—while the highly regarded German c’t magazine measured the output and concluded that it was out of spec, we’ve been assured that it is in spec. Regardless of whether the mini is in spec or not, the fact remains that ‘dim video’ is a reproducible problem and needs to be addressed.

High quality displays (such as Apple’s and a Samsung SyncMaster we tested) appear to automatically calibrate the display’s brightness and contrast to the signal level that is received. These displays automatically compensate for the mini’s VGA signal, and the problem is not observed.

Other monitors permit the user to manually request the brightness/contrast be adjusted to an optimal level. This action automatically calibrates the monitor to the received signal. (For example, the common NEC MultiSync monitors provide a handy Auto button.) Displays that offer neither fully automatic calibration nor user initiated calibration require manual intervention.

Monitor calibration isn’t a task Mac users are used to, as Apple’s vertical hardware integration handles that for us. The task is more common when dealing with commodity PCs, and when the operating system doesn’t handle color correction.

Unverified Solutions

ColorSync calibration does not remedy the mini’s video, though it can help minimize it somewhat. Since the output does not display white at full intensity, ColorSync can do no more than adjust other colors to the same white-displayed-as-grey value; pure whites will continue to elude you.

Some users have reported that using a different DVI to VGA adaptor solves the problem, but we were unable to verify that. Swapping out adapters had no effect that we could observe. (We have been told that some monitors have issues with ground pins, which is why some adapters work better with some monitors.)

Many users suspected that poor contacts were to blame, but our testing provided no data to support this hypothesis. We don’t doubt that some users’ video problems were related to this cause, but we suspect their efforts only improved the video, but did not fully correct the problem.

At least one user reported good results after under-clocking the GPU and VRAM. While we saw no difference when doing this, we’re told that it addresses a TMDS issue with some monitors.

Finally, ATI’s Radeon 9200 ROM version 124 drivers did not improve things, though ATI has indicated that it will correct the green display corruption some users see on DVI monitors while running 3D applications.

Verified Solutions

If your monitor is used only with a mini (or only shared with another mini), calibrate your monitor’s brightness and contrast to the mini’s video signal. (This may require the monitor’s manual.) It’s that simple. While monitor calibration is somewhat foreign for Mac users, it’s sufficiently common for PC users that most monitor reviews offer considerable focus to the calibration tools provided.

If you use a KVM to switch between a mini and another Mac, first calibrate the monitor to the mini. On the other Mac, create a custom ColorSync profile that adjusts the gamma to match the mini-adjusted display. We used this method to match several Macs to a mini’s video and an NEC monitor, all connected via an Avocent KVM.

If, however, you are switching between a mini and a PC, we have no easy solution to offer at this time. Windows offers no output calibration; a monitor calibrated to the mini causes Windows to appear washed out and lacking contrast at the bright end. (We’re told that QuickGamma offers some color correction for Windows, but we have not tested it in this situation.) A “think different” option is to consider changing to remote sharing software such as Timbuktu Pro or VNC; this solution routes all video output through one system. This isn’t suitable for gamers and users who need high display refresh rates, however.

If you are shopping for VGA displays, look for those that offer dual inputs and can calibrate each input independently. You lose the benefit of the KVM switching all peripherals for you, but the display problems will be resolved. Or, just buy a DVI monitor, as they don’t have this problem.

Last, we feel honor-bound to point out Apple’s support document that addresses this issue.

Mac OS X 10.4 Tiger

Mac OS X 10.4 doesn’t appear to offer any solution for mini owners on this issue. While some video related improvements are in 10.4 such as improved overscan display, dim video remains.