I got one working a little while ago. Here's how: You have to go to xfree86.org and download the new XF_SVGA server (latest version). Put this somewhere, and make it mode 755. (You have to untar it, etc... ; put the actual X server somewhere)
Now, edit /etc/X11/Xserver and change the first line to match the path and filename of the new server. You have mo make an XF86Config file. Use the text-mode xf86config program (note the case) to do so. At this point, it will start X but things may be very ugly. If they are, look in the README.SiS file on the xfree86.org site, and add all of the 'debugging' options listed there into your XF86Config file. At this point, everything should be pretty. If you like, you can try commenting out the debugging options, one at a time (with a # at the front of the line), until you see exactly which options you need. I believe that I had to turn on the 'no_bitblt' and 'sw_cursor' options; you may get diffreent results. This worked fine for me a woeek or two ago; hope it helps. If you have difficulty, mail me privately and I'll send you my (working) XF86Config file. Carl