[iyonix-support] Re: MDF for new monitor

On 15 Nov 2008 Richard Mellish <RichardMellish@xxxxxxxxxxxxxx> wrote:

> I've just acquired and installed a new large flat-screen monitor:
> connected via a KSB switch to both my Iyonix and my Windows PC. The PC
> immediately recognised it and gave me a choice of screen modes up to
> the monitor's native resolution of 1900x1200, which display perfectly
> without any need for adjustment, but I can't get a good display with
> the Iyonix.

I'd first try without the KVM switch attached, as if its a modern 
electronic one, it may interfere with the setting up. Once things are 
working you can add it back in.

> I've used MakeModes and tried tweaking numbers, both in the MakeModes
> window and by editing the file manually, but the least bad mode I've
> managed to get working so far is 1040x780 (i.e. 4:3 aspect ratio).

Is the monitor a proper computer monitor or a HD TV with RGB input?
If so it may not accept an analogue VGA input over 780p. Is the PC 
connected via analogue VGA, DVI-A, DVI-D or something else?

> Any mode that I try to create at a higher resolution, even the same
> 780 vertically but the correct 1.6 times that horizontally, produces
> one of other of:
> large black gaps at both the bottom and the right and the picture
> extending beyond the left-hand edge;
> Incoherent display, like an old TV with horizontal hold lost;
> "INPUT SIGNAL OUT OF RANGE" message.

Looks like it's a fussy one.

> I thought of noting the PC's settings and copying them to the Iyonix.
> The PC declares them as follows:

> Horizontal:
> Front porch: 48
> Back porch: 80
> Sync width: 32
> Scan rate: 74.04 kHz
> Active pixels: 1920

> Vertical:
> Front porch: 3
> Back porch: 26
> Sync width: 6
> Refresh rate: 59.950 Hz
> Active pixels: 1200

> Pixel clock 154.00 MHz

I thought the units for the porches might not be the correct units, 
but they add up to an expected line total of 2080 (154MHz/74.04KHz).
However that makes the sync pulse very short, a usual 1920x1200 would 
have a sync of around 175 to 200 and porchs totalling around 100-150
at 154MHz.

Of course you can't just plug those values in, you have to increase 
the proportion of the line that is sync and porches by raising the 
values and increasing the pixel clock to maintain the scan rate at 
74.04KHz.

> Significantly, there are no numbers for Left/Top border and
> Right/Bottom border, as called for by MakeModes. However it's not that
> the PC is hiding these numbers: dividing the 154 MHz pixel clock by
> the horizontal total and the vertical total gives the declared 59.95
> Hz frame rate. So it seems that the PC's graphics card doesn't bother
> with the borders that MakeModes wants.

No, if you divide the refresh rate by scan rate you get a total of 
1234 lines. So there is 34 lines of non display area, probably 3 lines 
of vertical sync, and 26 lines of back front / top border, and 5 lines 
front porch / bottom border.

> However setting exactly the same values in the MDF causes MakeModes to
> complain in the "Timing diagnostics" area that it needs some minimum
> values and, more importantly, causes the monitor to give the "INPUT
> SIGNAL OUT OF RANGE" message.

The parameter warnings are for a VIDC system and don't necessarily 
apply to the Iyonix fitted with a graphics card, but I've never had a 
mode not work if it conforms to VIDC limits.

Cheers
---Dave

-- 
______________________________________________________________________

David J. Ruck   Phone: +44- (0)7974 108301   Email: druck@xxxxxxxxxxxx
______________________________________________________________________
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