Thank you for your kind post, Zane.
You can test all the Framebuffers available or you can follow what i did below and see if that works for you.
Alopias
Alouatta
Baboon
Cardinal
Caretta
Colobus
Douc
Eulemur
Flicker
Galago
Gliff
Hoolock
Hypoprion
Iago
Kakapo
Kipunji
Lamna
Langur
Megalodon
Motmot
Nomascus
Orangutan
Peregrine
Quail
Raven
Shrike
Sphyrna
Triakis
Uakari
Vervet
Zonalis
Pithecia
Bulrushes
Cattail
Hydrilla
Duckweed
Fanwort
Elodea
Kudzu
Gibba
Lotus
Ipomoea
Mangabey
Muskgrass
Juncus
The reason why I selected "Zonalis" framebuffer was that "Zonalis" is the only framebuffer which has 6 display output.
The other framebuffer which has also 6 display output is "Bulrushes" but it is the one for ATI 6000 series not for 5000 series.
As I mentioned, V9800 has 6 mini-displayport output and HD5870 eyefinity6(which has identical 6 mini-displayport output as V9800) uses "Zonalis" framebuffer usually.
Can I try other framebuffer which is the one for three to five display output?
Or can I try "Bulrushes" framebuffer which is one for 6000 series?
V9800 has same cypress chipset as ATI HD5870.
The name, number of output and kind of output of framebuffers is as follows.
{"Colobus", 2}, // 5000 - lvds, dp
{"Douc", 2}, // 5000 - lvds, dp
{"Eulemur", 3}, // 5000 - dvi-i dl, hdmi, vga
{"Galago", 2}, // 5000 - lvds, dp
{"Hoolock", 3}, // 5000 - dp, dp, dvi-i dl
{"Langur", 3}, // 5000 - dp, dp, dvi-i dl
{"Nomascus", 5}, // 5000 - lvds, lvds, dp, dp
{"Orangutan", 2}, // 5000 - lvds, dp
{"Uakari", 4}, // 5000 - dp, dvi-i dl, dvi-i sl, hdmi
{"Vervet", 4}, // 5000 - dp, dvi-i dl, dvi-i sl, hdmi
{"Alouatta", 4}, // 5000 - lvds, dp, dp, dp
{"Baboon", 3}, // 5000 - dvi-i dl, hdmi, vga
{"Zonalis", 6}, // 5000 - dp, dp, dp, dp, dp, dp
{"Mangabey", 2}, // 5000 - lvds, dp