Hi! Radeon drivers are specific per Radeon microarchitecture and Radeon microarchitecture version.
The Radeon microarchitectures to date are TS 1, TS 2, TS 3, GCN 1, GCN 2, GCN 3, GCN 4, GCN 5 (TS = TeraScale and GCN = Graphics Core Next), in that ascending chronological order.  First, thank you very much jsg@ for that you committed full OpenBSD kernel support for the radeondrm(4) driver today!  Previously, while Xorg's radeondrm(4) driver supported all cards up to GCN 2, OpenBSD's kernel supported the Radeons up to GCN 1 only. The radeon(4) man page listed all cards up to GCN 2, but only the cards up to GCN 1 were actually supported by OpenBSD. jsg@'s diff today extends radeondrm(4) to support Radeons up to GCN 2. The major move with Radeon graphics cards today, is their move from the radeondrm(4) driver (called "xf86-video-ati" by Xorg and "radeon" on Linux) , to the "amdgpu" driver (called "xf86-video-amdgpu" by Xorg) . All new Radeon are driven by the amdgpu driver: The radeondrm driver supports all Radeon cards up to and including GCN 2. GCN 2 was released 2013 and the last GCN 2 card was released 2015. No more GCN 2 cards will be coming. The amdgpu driver supports all new Radeon cards from GCN 1.2 and up. This means the amdgpu driver is needed for GCN 3 and newer Radeons, and GCN 3 cards started coming to the market 2014. amdgpu(4) has not been ported to OpenBSD yet.  I am not perfectly clear about the max feature set in the GCN 2 cards, maybe I will make a post later about what you can and cannot do with amdgpu(4) (not yet ported) vs. radeondrm(4) cards, however more modern features like Displayport 1.4 and 1.3 support, support for higher resolutions, MST (Multi-Stream Transport), newer video codecs with higher resolutions etc., appear to be only in the newer GCN 5 and GCN 4 cards, which are supported only by the amdgpu driver. The Radeon GPU:s are important in OpenBSD's ecosystem as they are the only way to increase graphics functionality, that not involves changing CPU to Intel's latest, and hence change motherboard and other hardware. Do you have plans to port amdgpu? Would particular hardware donations or other donations be of help? Thanks, Joseph  https://en.wikipedia.org/wiki/List_of_AMD_graphics_processing_units https://en.wikipedia.org/wiki/Radeon https://www.x.org/wiki/RadeonFeature/  https://marc.info/?t=151664661500004&r=1&w=2  http://man.openbsd.org/OpenBSD-6.3/radeon.4 https://cgit.freedesktop.org/xorg/driver/xf86-video-ati/tree/ https://www.mankier.com/4/radeon https://manpages.debian.org/stretch/xserver-xorg-video-radeon/radeon.4.en.html  https://www.phoronix.com/scan.php?page=news_item&px=AMDGPU-DC-Accepted https://cgit.freedesktop.org/xorg/driver/xf86-video-amdgpu/tree/ https://en.wikipedia.org/wiki/AMDGPU https://www.x.org/wiki/RadeonFeature/ https://www.mankier.com/4/amdgpu https://manpages.debian.org/stretch/xserver-xorg-video-amdgpu/amdgpu.4.en.html  Those I talked to clarified this however also relevant refs: As seen by the absence of any "amdgpu" man page: http://man.openbsd.org/OpenBSD-6.3/amdgpu No "xf86-video-amdgpu" directory among the Xenocara drivers: https://cvsweb.openbsd.org/cgi-bin/cvsweb/xenocara/driver/ As of today on misc@ "amdgpu" has only been mentioned once, which was in the context of not being supported: https://marc.info/?t=151664661500004&r=1&w=2