xserver-xorg-video-sis multihead and int10 problem

I'm working in C3SL (Computer Science Center of Software Livre) at UFPR (Federal University of Parana).

In C3SL, I work with multiterminal systems. My team develop the MDM, Multiseat Display Manager (http://wiki.c3sl.ufpr.br/multiseat/index.php/Main_Page). We have to work with multihead systems.

Nowadays our software is Xorg 6.x capable, but we are working with MDM v2 and Xorg 7.6 and we are having a big problem of xserver-xorg-video-sis.

What's the problem?
In MDM v1 with Xorg 6.x, we can UP four monitors with four SiS pci, or mix 3 SiS pci with one onboard VIA or something like that.

With MDM v2 + Xorg 7.6, the SiS vga (at laboratory we use 315pro sis), when we start, for example, two sis and one via gpu, any SiS initialize.

Some erros appears:
- could not map MMIO area
- SisMapMem() failed
- xf86UnMapVidMem: cannot find region for [hexadecimals characters]

But if I use this option below, I cant start only one SiS card, and it Independence how many SiS cards I have in my test system.
Option "NoInt10" "Yes"
Option "RestoreBySetMode" "No"

When I use this option above, some new errors appears about memory size:
(EE) SIS(2): ERROR:
(EE) SIS(2): Virtual screen too big for memory; 1000K needed, 448K available
(EE) SIS(2): END OF MESSAGE

In the old times, when Xorg has -probeonly option, we could start all the cards with NoInt10 equal NO and then start X with all cards configured with NoInt10 equal YES. But nowadays we don't have -probleonly option and -pogo option (not documented) don't do anything to help.

I'm thinking about some problem in xf86 Xorg backend or something like that. But we have big problem with updated drivers for SiS too. winischhofer.net doesn't update it SiS drivers since 2006 and SiS Corp doesn't support old cards and the most new cards.

We tested many ATI, nVidia and VIA gpus, but nowadays our problem is how to use our system with latest Xorg and SiS cards. VESA driver doesn't help us. fb and sisfb too.

Some informations:
Ubuntu 10.04.1
X Version: 1.7.6
Released date: 2010-03-17
Kernel: 2.6.32-24-generic

Sincerely,
Francisco P K