It doesn't matter which resolution and/or refresh rate you setup for your monitor in the output-device variable in OBP, atyfb just wakes up at the default sun resolution of 1152x864. Doesn't check on the monitor EDID either. Reproducible: Always Steps to Reproduce: 1. Just boot gentoo sparc cd with a monitor uncapable of 1152x864. Actual Results: Monitor goes out of sync. Expected Results: Use settings from OBP output-device variable, or at least check monitor max resolution through EDID (if variable is empty). Note that Sun's OBP doesn't really care about the EDID anyway (V3 on ultra5). Workaround: Boot silo with the resolution you want "gentoo video=atyfb:xres:1024,yres:768" for example. Probably applies to other SPARC machines and framebuffers.
Replicated, now to find a resolution.
I've found on testing on a Blade 100 that atyfb will adhere to the resolution but not the refresh rate in OBP. However as there is no default across the board solution to this problem for all framebuffers, I've added a video.txt to the newest experimental LiveCD (gentoo-sparc64-1.4_rc4-11Aug2003.iso.bz2) that talks about ways to address this. If there's a better solution to this, feel free to post a followup
Due to the way sun framebuffers work and the fact that there's no unified video mode resolution settings like on x86, this really can't be fixed. I'll add it to the list of things to add to the FAQ however.
Adjusting status back to resolved:cantfix as bugzilla migration altered state.