Hello, Gentoo. Thanks to everybody who helped me get my video going in the other thread.
I've now got a more puzzling problem: Every time I boot up my new machine, the 1920x1080 pixel display is offset by around 2 inches from the left hand side (and aroun 1 cm from the top). It still appears to be 1920x1080 pixels (more precisely, 240 columns x 67 lines of 16x8 characters), but it's not filling the screen. The screen itself is attached to a KVM box, and it works just fine on the old machine. So it's not the physical display which is at fault. It's an around 10 year old Samsung digital monitor, not some ancient CRT, or anything like that. It's interface is a DVI cable. I seem to remember it filled the screen when it was new (on Monday). Part of my efforts to make the video work (see other thread) involved giving the kernel the drm.edid_firmware parameter. This parameter is intended to compensate for the display/KVM box/whatever failing to supply the correct EDID information to the PC. One of the settings I tried involved the offsets from the left and top mentioned above. But somehow they seem to have got stuck in the machine. It seems the BIOS has saved the offsets in the CMOS or something. I don't know how to undo these saved settings. Would somebody please help me on this, too. Thanks! -- Alan Mackenzie (Nuremberg, Germany).