On Wed, Jun 30, 1999 at 12:29:28PM +0200, Johann Spies wrote > On Tue, 29 Jun 1999, John Pearson wrote: > > > It may be worth checking in /var/log/xdm.log to verify that you *really do* > > have more than one video mode available. I have a NEC Multisync 2A upstairs > > that claims to do 31.5 & 35.15KHz; on some versions of XFree I've had to > > specify the horizontal ranges as "31.5,35.1-35.2" to get 800x600, on others > > "31.5,35.15" works. > > Thank you John. At the back of my monitor I have 31.5/35.2/35.5 indicated > as the horizontal ranges. /var/log/xdm-errors indeed reported that there > is only one mode - the others rejected because the frequency is not > correct. > > After changing my /etc/XF86Config to 31.5-35.2, 35.5 (it was 31.5, 35.2, > 35.5) I have more than one mode again. But I do not know whether that may > damage my monitor, so I put the original back again for the time being. > > Can I safely change 31.5, 35.2, 35.5 to 31.5-35.2, 35.5? >
I would, instead, change it to "31.5,35.1-35.2,35.5". Your monitor should be OK with that, but it won't like anything very far from the fixed frequencies it supports. Something like that works for me. My understanding is that the "actual" scan frequency is 35.15625 (36MHz dot clock / 1024 dots per row), which is 35.2 to 3 sig. figs. I believe that all that's happening is that some xserver versions check a result calculated to 3 sig. figs. (which matches 35.2), and some use 4 or more (which doesn't). If you look in xdm.log it will tell you why it doesn't like it, which should include the actual horizontal scan frequency required. Any range that includes that rate should work; it's up to you to be happy that it will work for you. Bear in mind that the accuracy of unstabilised, untrimmed quartz crystal oscillators is only between about 0.1% and 1% anyway (waves hands), so in practice the monitor has to have a little leeway built in. In summary, my understanding is that it's programming the exact same scan rate (it is derived from one of the 'standard' clocks (36MHz / 1024 dpl for 'standard' 800x600 mode), so it won't change unless you also change the number of dots per line in the mode definition), but that the new server is applying a more stringent test to your monitor, whose specs simply don't have enough significant figures to pass. Nonetheless, if it worked before it should work now. John P. -- [EMAIL PROTECTED] [EMAIL PROTECTED] "Oh - I - you know - my job is to fear everything." - Bill Gates in Denmark
