Here's the problem: you have a Sun workstation with two FFB (Creator, Creator3D, Elite) cards and you don't run Solaris. You want to change the resolution of the second card from the default to something higher, like 1600x1280x76. Under Solaris you use 'ffbconfig' to change the resolution on the fly, but there is no such utility under other OSes like Linux/SPARC.
The only alternative is to convince the OBP to set the resolution on the other head - the problem is, you can only set the resolution of the head that is the console head (especially on the FFB; on the CG6 there is a documented way to program the card for an arbitrary video mode without making it the console but I couldn't figure out how to do it on the FFB). That almost rules out changing the second head... but there is a way to cheat and make it work. Here's how you do it.
Edit your nvramrc (nvedit at the OBP prompt, google around for usage info if you don't know your way around the OBP line editor - the Sun docs are pretty good), and do something like this (example from my Ultra80 2xC3D):
probe-all
setenv output-device /SUNW,ffb@1d,0:r1600x1280x76
install-console
setenv output-device /SUNW,ffb@1e,0:r1600x1280x76
install-console
banner
Then you need to enable use of the nvramrc by setting use-nvramrc? to true:
setenv use-nvramrc? true
Reset the machine and you should be all set if you did it right. This should also work with other cards than the FFB since it doesn't do anything specific to the FFB cards, for example: a FFB + CG6 configuration in an Ultra 1 or 2. I haven't tried it myself though.
This little nvramrc script tells the OBP that the second head (ffb@1d) is the console head, so the OBP sets the resolution there, then the script immediately flips the console head back to the primary (ffb@1e) and proceeds normally. This works because the OBP doesn't de-initialize the second head when switching back. See the Sun Framebuffer FAQ for more info on stuff like supported modes on the Creator. Have fun ;-)