forcing use of vesa driver for x ??

Gene Heskett gene.heskett at
Fri Oct 9 17:25:08 UTC 2009


I have 2 boxes that run the machine control program 'emc'
One is kubuntu-6.06 LTS and one is ubuntu-8.04 LTS

Because the radeon and the nv drivers both lockup the interrupts for extended 
periods of time, the vesa driver which does not do that, is the driver of 
choice for this service.  All the others play hell with RTAI, messing with 
the steadiness of the heartbeat going to the motors which in turn can cause a 
stepper motor to stall, and stalled motors usually=wrecked parts.

I just found the 6.06 box has reverted to using the nv driver, which triples 
the IRQ latencies to the point of making RTAI useless, and I just traced some 
display problems down to the radeon driver on the new 8.04 LTS box that is a 
clean install.

I have found that my carefully crafted xorg.conf file on the 6.06 machine has 
been replaced by whatever X now thinks is correct, due to an update I 
suppose, but which wrecks how this program works, and which wrecks parts 
being carved.  I wrecked 3 parts before I discovered this.

I just tried to specify vesa in the device section on the 8.04 install, but 
the reboot upchucked and it then appears to have re-written the xorg.conf and 
the backups too, with a default that runs a 1920x1250 capable screen (its a 
22" samsung tv in fact) and will not run it at anything above 800x600, 
grossly fuzzified and  totally unusable for the task it must run.

So it is imperative that I restore the use of the vesa driver to both of 
these boxes.

How can I restore these two boxes to using the vesa driver, AND prevent X 
from overwriting these xorg.conf's to suit itself?


Cheers, Gene
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