Hi and welcome to LQ,
You can compile just the driver:
Get the latest driver source from here
and after extracting run:
Don't forget to make a backup of the 2 old driver files (neomagic_drv.so, neomagic_drv.la)
I don't have such a video card to test, but the driver compiles just fine in my Slack64. I had only to copy the 2 files from /usr/lib/xorg/modules/drivers to /usr/lib64/xorg/modules/drivers. If you run a 32bit Slackware you don't need to do this.