Resolved PM G4 MDD FW800 + display weirdness

[ToniCH]

Specs:
1. PM G4 MDD FW800 1.25DP
2. Original Radeon 9000 Pro (DVI and ADC -connectors)
3. OS: Sorbet Leopard
4. Display I've been using while testing: Samsung S24B300B -display with DVI- and VGA -connectors. DVI-cable used is DVI-D single link.

Problem: if I boot with any resolution bigger than 1280x720 the initial boot screen is fine but when desktop appears the screen is scrambled and partially shifted to right wrapping back on the left (pic attached).

I can just see where settings are and select them until I hit 1280x720 and then screen resets to normal. If after that I reselect for example 1080P it works fine.

Or I can unplug the display (when screen is scrambled) from the DVI-connector and replug it and the screen works properly at any selected resolution. And if I first boot 1280x720 and then select any bigger resolution it works too.

Its a bit annoying if I forget to set the resolution back to 1280x720 prior shutdown.

So, what do you think could cause this? It has not happened with any other Macs I've tried with that display.

Ps. I guess I need to make some room so I can test if this problem exists with my ACD 23" too.

 

[ToniCH]

Ok, so I tested it with the Apple ACD 23" and it works fine. So, the problem is probably some timing mismatch between the Samsung and the computer. Case closed.

And here I am visiting the forum with the G4.

 

[Amethyst1]

So, the problem is probably some timing mismatch between the Samsung and the computer. Case closed.

You could extract the display’s EDID using SwitchResX and (let us) have a look at the timing.

That being said, “1080p” requires e.g. 138.5 (CVT-RB) or 148.5 MHz (HDMI) pixel clock. The 23” ACD requires 154 or 155 MHz IIRC so unless the Samsung uses a weird timing with, say, huge blanking intervals, it shouldn’t run into a pixel clock limit.

 

[ToniCH]

Honestly, I have no idea why the problem occurs and only when booting. Something happens the moment desktop appears and the Samsung cannot display the 1080p resolution correctly. But it works perfectly when I manually choose smaller resolution and go back to 1080p. Or like I said unplug-replug the display cable.

Weird, but no biggie as I only use the Samsung for installation of "new" computers if I cannot do it in my "lair" due not having enough space to do it.