Unfortunatelly for my case, R420 and R481 are AGP 8x chips, and all cards I found is only 1.5/0.8V versions, so unusable with Efika and Pegasos2.
The only difference I found in MOS graphics setup between Efika/Pegasos2 is Double/Triple buffering. I don't think that it is the case, but I will check it also.
And of course, I will try the serial debug.
And last thing what I want to test is to setup autoboot directly to usb MorphOS 3.15 hdimage. And check if default image have some more tolerant graphics setup.[ Edited by sailor 14.01.2021 - 07:43 ]
Pegasos II 1.33GHz, AmigaOne X1000, Powermac G5 Quad, iMac G5, Powerbook G4 and Z10PE-D16 WS
MorphOS, AmigaOS, Debian, Ubuntu, OSX, NetBSD, Win7