Created attachment 697145 [details]
Xorg.0.log from i586 TW host a-865

Mailing list thread starter:
https://lists.opensuse.org/opensuse/2016-08/msg00322.html
(same with kernels 4.7.x as with kernel 4.6.4) :
# Xorg.0.log excerpts
X.Org X Server 1.18.4
[    57.691] Current Operating System: Linux a-865 4.7.4-1-default #1 SMP Thu
Sep 15 09:03:59 UTC 2016 (6a5bbb1) i686
[    57.691] Kernel command line: root=LABEL=os133SS25 ipv6.disable=1
net.ifnames=0 noresume splash=0 vga=791 video=1024x768@60 3
[    58.342] (EE) open /dev/dri/card0: No such file or directory
[    58.382] (EE) MGA(0): Unable to map Framebuffer F0000000 2000000.  Invalid
argument (22)
[    58.382] (EE) MGA(0): Unable to detect video RAM.
[    58.382] (EE) Screen(s) found, but none have a usable configuration.
[    58.383] (EE)
[    58.383] (EE) no screens found(EE)...

I didn't update this installation for many months, which explains large gap
between installed kernels. Xorg and vttys work as expected with kernel-pae
4.2.3 and vga=791 on cmdline, but vga= needs to be omitted with the newer
kernels for Xorg to start. Omitting vga= from cmdline results in far too few
columns and rows on the vttys. I looked on bugs.freedesktop.org but found
nothing like this. I tried a fresh zypper up, but kernel-default 4.7.6 with
vga=788 proved no better, as did kernel-vanilla. Also didn't help adding to
xorg.conf device section either VideoRam 16384 and/or Option "OldDmaInit" "On".

# zypper se -si | egrep 'x11-serv|mga|kernel'
il | kernel-default                       | package     | 4.7.4-1.1            
         | i586   | (System Packages)
il | kernel-default                       | package     | 4.6.4-2.2            
         | i586   | (System Packages)
il | kernel-default                       | package     | 4.7.6-1.1            
         | i586   | OSS
i  | kernel-firmware                      | package     | 20160913-1.1         
         | noarch | OSS
il | kernel-pae                           | package     | 4.2.3-1.4            
         | i686   | (System Packages)
i  | kernel-vanilla                       | package     | 4.7.6-1.1            
         | i686   | OSS
i  | nfs-kernel-server                    | package     | 1.3.4-2.2            
         | i586   | OSS
i  | xf86-video-mga                       | package     | 1.6.4-2.2            
         | i586   | OSS
i  | xorg-x11-server                      | package     | 7.6_1.18.4-1.2       
         | i586   | OSS
# lspci | grep VGA
01:00.0 VGA compatible controller: Matrox Electronics Systems Ltd. Millennium
G550 (rev 01)