Found from https://linuxforums.org.uk/index.php?topic=12330.0

These instructions are workable, but xserver-xorg-video-sisimedia_0.9.1-1_i386.deb does not install if dependency xorg-video-abi15 is not removed form DEBIAN/control file. For getting workable installation package, extract and edit the package, and rebuild a new fixed installation package.

sudo chown root:root -R xserver-xorg-video-sisimedia_0.9.1-1_i386

sudo dpkg -b xserver-xorg-video-sisimedia_0.9.1-1_i386 xserver-xorg-video-sisimedia_0.9.1-1_i386-fixed.deb

Also xorg.conf file must ne copyed to /etc/X11

sudo cp xorg.conf /etc/X11/xorg.conf

If configuration does not work, remove xorg.conf file

sudo rm /etc/X11/xorg.conf

Tested using old FUJITSU SIEMENS Amilo A1645

Operating system: antiX 16

A ready package + xorg.conf can find from here.

Read also How to use vesa graphic driver