So I recently picked up an Atlona DP-400 Dual Link DVI to Mini DisplayPort converter very cheaply, and used it to connect my 15in PowerBook5,6 (early 2005 1.67 GHz with dual-link DVI) to my Dell P2415Q monitor.
The good news is that 3840×2160 at 30 Hz works and is displayed properly at first glance. Panther, Tiger and Leopard are really majestic at that resolution, even though the monitor's size (23.8 inches) makes everything very small (I'll say I like it that way, however
).
However, there's framebuffer corruption (i.e. it also shows up on screenshots, not just the monitor itself) going on starting at a width of about 2660 pixels. Windows seemingly disappear when they're dragged across that boundary, and dragging them back reveals that the wallpaper is showing in the parts that were across the boundary. The desktop itself including the menu bar and icons and full-screen applications are not affected, though.
This screenshot illustrates the problem - the right part of the Safari window simply disappears:
2560×1440 at 60 Hz works perfectly. I'll have to see (1) if I get a similar behaviour when running Linux on the PowerBook and (2) if this problem disappears on Mac OS X when using a resolution that's not wide enough to run into this boundary; e.g. 2624×2160 or something like that - UPDATE: no problems at 2656×2160.
I'm fully aware of the fact that the PowerBook's GPU never "supported" resolutions higher than 2560×1600 but it's fun to see how far one can make the old machines go...
The good news is that 3840×2160 at 30 Hz works and is displayed properly at first glance. Panther, Tiger and Leopard are really majestic at that resolution, even though the monitor's size (23.8 inches) makes everything very small (I'll say I like it that way, however

However, there's framebuffer corruption (i.e. it also shows up on screenshots, not just the monitor itself) going on starting at a width of about 2660 pixels. Windows seemingly disappear when they're dragged across that boundary, and dragging them back reveals that the wallpaper is showing in the parts that were across the boundary. The desktop itself including the menu bar and icons and full-screen applications are not affected, though.
This screenshot illustrates the problem - the right part of the Safari window simply disappears:

2560×1440 at 60 Hz works perfectly. I'll have to see (1) if I get a similar behaviour when running Linux on the PowerBook and (2) if this problem disappears on Mac OS X when using a resolution that's not wide enough to run into this boundary; e.g. 2624×2160 or something like that - UPDATE: no problems at 2656×2160.
I'm fully aware of the fact that the PowerBook's GPU never "supported" resolutions higher than 2560×1600 but it's fun to see how far one can make the old machines go...
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