As you have seen, the "radeon*" and "radeondrmkmsfb*" drivers do not attach on "r100" class devices. They have been explicitly excluded because early in the DRMKMS integration in NetBSD, they exhibited the "(almost) black-on-black" video problem described in:
http://mail-index.netbsd.org/current-users/2015/02/20/msg026732 and later in the following PR: kern/49744: console is blank drm2/radeon The suggestion for "radeonfb*" is interesting. I see it's in the "ALL" kernel, but not in "GENERIC" (not even as a commented-out device), so you'd have to compile a custom kernel with it added to the config. -- |/"\ John D. Baker, KN5UKS NetBSD Darwin/MacOS X |\ / jdbaker[snail]consolidated[flyspeck]net OpenBSD FreeBSD | X No HTML/proprietary data in email. BSD just sits there and works! |/ \ GPGkeyID: D703 4A7E 479F 63F8 D3F4 BD99 9572 8F23 E4AD 1645