4.10. When I boot, the screen goes black and loses sync!

This is a known problem with the ATI Mach 64 video card. The problem is that this card uses address 2e8, and the fourth serial port does too. Due to a bug (feature?) in the sio.c driver it will touch this port even if you don't have the fourth serial port, and even if you disable sio3 (the fourth port) which normally uses this address.

Until the bug has been fixed, you can use this workaround:

1. Enter -c at the bootprompt. (This will put the kernel into configuration mode).
2. Disable sio0, sio1, sio2 and sio3 (all of them). This way the sio driver doesn't get activated -> no problems.
3. Type exit to continue booting.

If you want to be able to use your serial ports, you'll have to build a new kernel with the following modification: in /usr/src/sys/i386/isa/sio.c find the one occurrence of the string 0x2e8 and remove that string and the preceding comma (keep the trailing comma). Now follow the normal procedure of building a new kernel.

Even after applying these workarounds, you may still find that X Window does not work properly. Some newer ATI Mach 64 video cards (notably ATI Mach Xpression) do not run with the current version of XFree86; the screen goes black when you start X Window, or it works with strange problems. You can get a beta-version of a new X-server that works better, by looking at the XFree86 site and following the links to the new beta release. Get the following files:

AccelCards, BetaReport, Cards, Devices, FILES, README.ati, README.FreeBSD, README.Mach64, RELNOTES, VGADriver.Doc, X312BMa64.tgz

Replace the older files with the new versions and make sure you run xf86config again.