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GeordieBoy

Thu Jul 24 2008, 08:01PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Does anyone know what causes speckles on the PC display when windows in XP are scrolled or resized?

I've just bought a 22" 1680x1050 LCD panel for my computer and had to upgrade the video drivers and flash the system BIOS to get it to work at native resolution. Apparently this is to upgrade VBIOS to support widescreen modes as it's a motherboard with onboard SiS660 video controller.

Now I have a beautifully clear widescreen desktop in vibrant colours. The only minor annoyance is that when I scroll up and down a window or drag the corner to resize it i get momentary white and black lines and speckles all across the screen. Resizing a small window causes just a few insignificant dots, whilst draging the corner of a large window fills the screen with a shower of white snow and horizontal "dashes".

I seem to remember reading something about PCI bandwidth causing this problem, but the PC will play DVDs and DivX video fine either in a window, or in full-screen mode. Both PowerDVD and Win Media Player play movies fine. The psychadellic "visualisation" thing when playing music in Media player makes the screen go nuts though for the first few seconds then it seems to sort itself out and run smoothly.

The only thing that i've found to make the problem go away is selecting a lower resolution than 1680x1050 (which results in bluring/aliasing as it's not the native resolution of the panel) _OR_ selecting 16-bit colour depth instead of true-colour but this causes DVD and movie playback to show colour banding which isn't ideal.

Do I need to try messing around with settings in the BIOS, or just live with it? Any tips or shared experience would be welcomed. Thanks in advance.

-Richie,

Ken M.

Thu Jul 24 2008, 08:50PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

As much as I've dealt with pc's construction and troubleshooting...I'm not quiet sure, But I doubt you would have to deal with it, unless you neither can afford or ar unable to aquire a more powerful video card. But if you just want a guess, I'd say you are running a resolution that the video isn't able to operate, or at least is unstable at operating.

reign

Thu Jul 24 2008, 11:42PM

Registered Member #260 Joined: Sun Feb 26 2006, 09:51PM
Location:
Posts: 17

Coming from my experience as a computer technician, this issue sounds like it is related to video memory/hardware.

Is this an on board graphics chip or an addon card? I've seen this problem before and it is caused by corruptions in video memory due to either a faulty graphics processor, faulty graphics memory, or an overheating condition.

The reason it doesn't show up under lower resolutions/bit depths is that the card is working less, using less memory, and running cooler.

You can try borrowing a friends video card to see if you experience similar issues. Also, if this is an on board video processor , your huge display may be maxing out its limited memory causing the visual artifacts.

Hope this information helps!

Steve Conner

Fri Jul 25 2008, 05:53PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

It could be bad memory as others have suggested, or it could be bus contention, since integrated graphics chips often share the main system memory, which only has so much bandwidth. Maybe they only tested the motherboard design up to 1280x1024. DVD playback isn't really a hard test, since any graphics controller chip worth its salt can upscale, so the full-sized image only has to traverse the bus once. When drawing windows, the data may need to be blitted back and forth several times, especially by Microsoft ;)

Either way a new graphics card should be an elegant solution

Or try reducing your frame rate, if it's 72Hz put it down to 60, if it's already 60 reduce it to 50 if possible. I guess you could also try optimizing the memory controller settings in the BIOS, if you haven't already done so. Oh, and play with the "Graphics acceleration" slider in the XP control panel. Or maybe even turn off "Draw window contents while dragging"...

GeordieBoy

Fri Jul 25 2008, 08:36PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

Wow, lots of great tips here! Thanks for all the suggestions guys. The video is indeed onboard the motherboard and it likely was never intended to support huge widescreen monitors. I had to download a BIOS patch from a 3rd party which includes the latest SiS VBIOS for my on-board video chip patched into the ASUS mainboard BIOS because ASUS didn't update it to support 1680x1050 themselves.

It works flawlessly on all resolutions below 1680x1050 and also works fine at that resolution in 16-bit hi-colour mode. Refresh rate is set to the LCD panel's recommended value of 60 which is the lowest in the drop down menu. I tried 75 and 85Hz but the panel said it was still receiving 60 and it didn't change anything.

At the moment i'm like 95% happy and amazed by the massive amount of desktop workspace! ...and only distracted by the occasional sparklies so I'll probably live with it for the short term. I think Dr Conner might be onto something with the bus contention thing. It is only when forced to redraw large areas of the screen when the sparklies appear. Once it gets settled into playing DivX or DVD video it sails along smoothly.

I will try playing about with the "Graphics Aperture size", "PC bus latency timer", "Video memory cache mode" and "Onboard VGA share memory size" settings in the BIOS to see if any of these make a difference! I haven't messed about with all the DDR RAM pre-charge cycle stuff yet for two reasons. 1) By default it says it is all configured automatically by SPD? and 2) I haven't got the foggiest idea what it all means!

Thanks again for all the suggestions,

-Richie,

reign

Fri Jul 25 2008, 11:23PM

Registered Member #260 Joined: Sun Feb 26 2006, 09:51PM
Location:
Posts: 17

GeordieBoy wrote ...
It works flawlessly on all resolutions below 1680x1050 and also works fine at that resolution in 16-bit hi-colour mode. Refresh rate is set to the LCD panel's recommended value of 60 which is the lowest in the drop down menu. I tried 75 and 85Hz but the panel said it was still receiving 60 and it didn't change anything.

That right there leads me to believe that you are indeed maxing out your graphics controller's capabilities. I think you may want to look down the path of an upgrade, especially if you intend to do any gaming. :)

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