On Nov 10, 2008, at 6:24 AM, Andy wrote: > A friend’s G4 iBook is displaying strange video behaviour. Pink and > blue artifacts appear on the screen from boot up onwards. Also > images from windows leave their impression behind when closed. This > can sometimes be ‘cleaned up’ by draging another window across. > I suspected video RAM but it doesn’t happen when booted from the > system disk. However it is still present after a nuke and pave > install. > Hard drive checks out ok so what could cause this with a clean > install (seems obviously hardware) yet doesn’t appear when booted > from a Tiger DVD (software issue?)
This is truly a odd issue. I agree with your diagnosis. It appears to be VRAM related, and the fact that it doesn't do it from the DVD is strange indeed, especially since you did a clean reinstallation on the HD and it continued. I'm thinking of a couple simple long shot ideas and a more complicated idea that's more likely. First, could it be something as simple as an odd fresh rate, perhaps too fast for the LCD? Seems highly unlikely. These are normally not adjustable in the Displays System Preference for laptops. Second, it could possibly be something in the PRAM/NVRAM, so I'd zap the PRAM and reset the NVRAM and see if anything changes. Third, and probably the most likely to produce the desired results, it sounds identical to the problem that occurs with the GPU or VRAM bus speed is set too high for the physical VRAM chip speed. Perhaps some of the VRAM chips are under-specification? The solution is rather simple. Download the application ATIcellerator II and install it. Then "under-clock" the processor and/or VRAM bus speed until you find something that works. I'd probably start with a 10-15% under-clock on both see if it eliminates the issue. Proceed by trial and error to find the least underclock that produces an artifact free display. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
