The package XFree86-SVGA-3.3.6-33.i386.rpm (RedHat 7.0) doesn't work properly with the graphics card S3 86C390. But there isn't any problen whith XFree86-SVGA-3.3.6-20.i386.rpm (RedHat 6.2)
I have the same problem. It is Red Hat Linux 7.0, and the same problem happens with the Trident GUI 9680, 2.0 MB onboard RAM, and uses a Trident Built-In 15/16/24 bit DAC. However, when tried using Xconfigurator, it seemed to generate the improper file, when using the new X Free86 server, but if you use the old one (the server XF86_SVGA executable that came with version 6.2), with a configuration file that comes from the same 6.2 release, it works the config set by Xconfigurator. It looks like the config file rather than being replaced is just altered, and the default config on the 7.0 isn't working at all with the Trident.
Why aren't you using XFree86 4.0.x?
XFree86 3.3.6 has been updated in all currently supported releases of Red Hat Linux (7.1/7.0/6.2), and contains many S3 driver improvements and bug fixes. This release is available currently at: ftp://people.redhat.com/mharris/testing/ A newer release of XFree86 4.0.3 is there as well. When configuring 3.3.6 use: Xconfigurator --preferxf3 --nodri If using 4.0.3, call "Xconfigurator --preferxf4 --nodri" instead.