I've been running in circles attempting to diagnose some garbled text when something is highlighted on screen. At first I assumed it was a RAM issue because I had been reconnecting traces on the problem board, but I've now encountered the issue on two Mac II's and a IIx. Snooper and APD have not found any issues with RAM. I have two Toby NUBUS graphics card and an Apple Display Card 8*24 where text gets garbled. I've booted from a BlueSCSi and a floppy disk and it persists. It seems to only happen on 256 colors. Millions is fine. I'm using a Dell LCD display with a DB 15-pin->VGA adapter, maybe that's all it is? I only have LCD displays so it's difficult to rule that out as the culprit. I mostly want to confirm that this is not an issue on the logic board so I can move on with repairs.
Mac II Video glitch
- Thread starter blturner
- Start date
Very interesting.
It isn't the LCD.
1. Does it happen every single time in 256 mode?
2. Is the scrambled text always scrambled the exact same way or does it look randomly scrambled differently each time?
I think my initial diagnosis was incorrect, the scrambling is happening at 4, 16, and 256. I attempted to record the monitor changes to better illustrate what I'm seeing.
Here is the Toby card without the RAM expansion, only supports 16 colors:
Here is the Toby card with the RAM expansion and 256 colors:
Here is the Toby card without the RAM expansion, only supports 16 colors:
Here is the Toby card with the RAM expansion and 256 colors:
It's hard to tell, but I think the scrambling does look the same each time.
And, it is only scrambling inverted text. That's a clue.
Have you tried booting with extensions disabled?
Have you tried booting with extensions disabled?
It's 7.1 from the Legacy Recovery CD image. I also have a 7.5 install on this SD card I booted from just now and the issue is there as well. Could it be the VGA adapter I have? That's the only common denominator besides the display and the BlueSCSI. I'd have to check again, but I don't think I've seen this issue on a IIci I had hooked up with this adapter (but different video card) and display during #MARCHintosh.
I took the Toby card and VGA adapter and put them in the IIci and there was no highlight glitching, so it must be something specific to the II(x). I have a 256k and 512k ROM, so I swapped the 256k with the 512k, but no difference.