Heroes Of Might And Magic V works under Wine. However, when running with DRI - textures are missing. In the main menu there is no background, in game mode almost everything is white. Everything works correctly on same system when using fglrx driver. Radeon X550 PCI-E, Mesa-6.5.2, xf86-video-ati-6.6.3, wine-0.9.29, tested on Heroes Of Might And Magic Demo
I'd suspect it's got something to do with texture compression. There are quite a few direct3d apps which absolutely require dxtc. So make sure you have s3tc enabled. Just a guess though...
You were right, after installing libtxc_dxtn060508 Heroes Of Might And Magic V demo works correctly with DRI on Radeon X550.
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