On 26 Jan, Peter Chubb wrote:
> It's not actually that hard to calculate the modeline.
>
> You need to know the maximum clock frequency and vertical refresh
> frequency of your monitor, and the minimum vertical and horiz sync
> times.
>
> Then the modeline is in two halves -- horizontal and vertical.
> I usually use the new format now.
>
> Then your modeline will be something like:
> Mode "1920x1440"
> DotClock 300 # Max frequency
> HTimings 1920 Hxxxx Hyyyy Hzzzz
> VTimings 1440 Vxxxx Vyyyy Vzzzz
> EndMode
>
> where Hxxxx is 1920 plus how many dot clocks after the scan before
> the horizontal sync pulse, Hyyyy is Hxxxx plus the Hsync width divided
> by the dot clock, and Hzzzz is the total time for each horzontal scan.
Ah. Yes, I remember the problem I had, now: not enough knowledge. :-)
How do you work out the horizontal sync pulse? If X says:
(II) NV(0): Supported additional Video Mode:
(II) NV(0): clock: 229.5 MHz Image Size: 392 x 294 mm
(II) NV(0): h_active: 1600 h_sync: 1664 h_sync_end 1856 h_blank_end 2160
h_border: 0
(II) NV(0): v_active: 1200 v_sync: 1201 v_sync_end 1204 v_blanking: 1250
v_border: 0
(II) NV(0): Serial No: 24-CD405
(II) NV(0): Monitor name: IBM C220P CRT
(II) NV(0): Ranges: V min: 50 V max: 160 Hz, H min: 30 H max: 130 kHz,
PixClock max 370 MHz
(II) NV(0): end of DDC Monitor info
(==) NV(0): Using gamma correction (1.0, 1.0, 1.0)
(II) NV(0): IBM C220P CR: Using hsync range of 30.00-130.00 kHz
(II) NV(0): IBM C220P CR: Using vrefresh range of 50.00-160.00 Hz
(II) NV(0): Clock range: 12.00 to 350.00 MHz
I assume this means the maximum clock frequency is 350 MHZ (dot
clock 350)? Or is it PixClock max, 370? And if the manual says it can
do 1920x1440 at 85HZ, then that means the vertical frequency is 85? The
minimum vertical and hztl sync times ...? I have no idea. Are they
related to V min (50) and H min (30)? What is the hsync width?
Sigh. There are just too many variables that I don't have a definition
for, and only a vague understanding of. :-(
> Vertical timings are similar.
>
> Anyway, the standard VESA GTF timings for 1920x1440 are close to:
>
> Mode "1920x1440"
> DotClock 341.35
> HTimings 1920 2072 2299 2656
> VTimings 1440 1441 1444 1512
> Flags "-HSync +VSync"
> EndMode
>
> And for [EMAIL PROTECTED] they are
>
> Mode "2048x1536"
> DotClock 340.5
> HTimings 2048 2216 2440 2832
> VTimings 1536 1537 1540 1603
> Flags "-HSync +VSync"
> EndMode
>
> You can tweak them a little if you need to.
I tried this in the Monitor section:
Mode "1920x1440"
DotClock 350
HTimings 1920 2072 2299 2656
VTimings 1440 1441 1444 1512
Flags "-HSync +VSync"
EndMode
Mode "2048x1536"
DotClock 350
HTimings 2048 2216 2440 2832
VTimings 1536 1537 1540 1603
Flags "-HSync +VSync"
EndMode
But got the error:
Parse error on line 59 of section Monitor in file /etc/X11/XF86Config-4
Unknown flag string
(EE) Problem parsing the config file
(EE) Error from xf86HandleConfigFile()
By commenting out the Flags lines, I was able to get the 2048x1536 mode
to work, though the 1920x1440 mode looks dangerous - the screen sort of
folds back over itself and looks dark. You can recognise where the
windows (folded horizontally) are.
Should I have left the DotClock at your 341.5, or perhaps tried 370?
Does that affect the other numbers? Since it divides the dot clock,
you said, I thought it should.
Sorry for being so thick.
luke
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