I set up XF86 4.0.1 on my computer recently, with a really nice 21" ViewSonic
PT810 on one output, and a really crappy 14" NEC Multisync 2A on the other.
Thanks to Yaron, I have good modelines for the ViewSonic (from my XF86
3.3.6 setup); however, the NEC won't work with any default mode other than
640x480 at 60Hz.

so in case anyone else out there has to deal with one of these monitors
under X, here's my collection of notes on what I did and learned.

to configure the NEC, I set it up as the primary monitor, so when I launched
xvidtune, it would read and adjust that one.

I guessed up a modeline by going to http://zaph.com/Modeline/; and putting
in the desired resolution and refresh rate. I put that in the XF86Config
file, and launched X. the NEC display would be screwed up, but the ViewSonic
would be fine. So I launched xvidtune, and dragged it over to the Viewsonic
screen. where I could see what I was doing. :)

I clicked on the 'Auto' button, so changes would take effect immeditately;
then tried adjusting various values to see if that would produce a working
resolution. for this monitor type, clicking on the 'Narrower' button would
usually eventually produce a working mode, albeit at a lower refresh rate.

this NEC Multisync, despite it's name, doesn't want to work for a very wide range of refresh rates. 

this monitor doesn't have a horizontal width adjustment, nor a degauss
button. this seriously sucks. because of this, one needs to adjust the
horizontal width, with the modeline. (and the wider the display is 'painted'
on the screen, the lower the refresh rate will be).

I know that I had one of these monitors running at 1024x768 once, but that was with a DOS program written by NEC to show off their monitor.

according to Xconfigurator's MonitorsDB file:
for the NEC Multisync 2a (guessed from the 2V)
hsync range 0:  30.00 -  57.00
vsync range 0:  50.00 - 100.00

# in order, the modeline numbers are:
# "name"  dotclock  hdisp hsyncstart hsyncend htotal   vdisp vsyncstart vsyncend vtotal
# 640x480 @ 69Hz
"640x480"      27.30    640  644  676  776    480  482  484  504
# 640x480 @73Hz
"640x480"      29.50    640  644  676  808    480  482  484  501

# 800x600 @ 58.61Hz
"800x600"      44.18    800  880  928 1208    600  602  604  624
# 800x600 @ 54.43Hz (but fills the screen wider than the above modeline)
"800x600"      33.65    800  804  844  960    600  606  608  644

Carl.
-- 
Network Engineer
Real-Time Enterprises
(952) 943-8700