[CentOS] Completely lost X (was system-config-display wronglysets up Viewsonic VG730m monitor)

[John R Pierce]

Anne Wilson wrote:
>> I was reluctant to state this because I have no authoritative knowledge
>> on these things but if you change video cables, I think that you need to
>> reboot to get the video chipset to properly recognize the cable/monitor
>> connected.
>>
>>     
> I'm pretty sure you do.  I had done that, though.
>   

on VGA, yes, the video controller can only read the "VESA ID" extended 
format information when its reset, its a horrible mess of a kludge 
interface as IBM had only alloted like 3 pins for a 1-of-8 model monitor 
specification back in 1984 or whenever the first VGA was designed.    
VESA created this very complex dance where the V sync line is used to 
clock serial data over those pins, and its only read when the monitor 
sync is stopped for some length of time, then started, the video 
controllers capture this data and save it so the host can later read 
it.    I forget all the specifics, I had to work with this stuff in the 
mid 1990s when it was devised.

I /think/ on DVI its a lot better, but I've not actually worked with 
that at a low level so I can't confirm this from direct experience.