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Apple II+ graphical glitching


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#1 ubersaurus OFFLINE  

ubersaurus

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Posted Sat Dec 29, 2018 2:30 PM

I'm trying to prep my Apple II for Magfest, and noticed some unusual graphical problems when trying to boot games. This occurs off the cffa and the actual Disk II drive. The bottom quarter of the screen in gameplay is full of garbage characters, while the loading screens have random characters basically the whole way through. Anyone know what the problem could be? Or how I can best find out?

I also got another error trying to load Dino eggs off the cffa. Not sure what that's about - I don't recall seeing it before. Still boots off the cracked disk, though? The cffa self test found no issues.

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#2 Aunty Entity OFFLINE  

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Posted Sat Dec 29, 2018 3:52 PM

Memory? Seeing as it looks reasonable stable across the bottom there? 



#3 Lee Adamson OFFLINE  

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Posted Sat Dec 29, 2018 5:09 PM

I believe there's a soft switch that turns the 4-line text area in hgr mode on and off.  I think it's handled by the IOU chip, but I wouldn't swear to it.  Could maybe be the MMU instead(?).  My guess would be that something's not right with that, and it's not telling the video stuff to go full HGR mode so it's still pulling some junk out of the text page (which is probably being used for something else).

 

Unfortunately, I'm too ignorant to suggest anything to fix it, other than to try reseating the IOU, MMU, and video chips.



#4 Keatah OFFLINE  

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Posted Sat Dec 29, 2018 5:27 PM

I'll second the softswitch mode of failure. But, the II+ doesn't have MMU or IOU chips. It's all discrete.

 

Perhaps look around F14, F13, or things to do with the nearby LS257 or LS259 chips.


Edited by Keatah, Sat Dec 29, 2018 5:45 PM.


#5 The Usotsuki OFFLINE  

The Usotsuki

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Posted Sat Dec 29, 2018 5:41 PM

C052/C053 softswitch



#6 ubersaurus OFFLINE  

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Posted Sat Dec 29, 2018 6:42 PM

I did a diagnostic program and it said the rom and ram chips are all good, so softswitch does seem likely - someone elsewhere pointed out it looks like an issue with the text/graphic modes intermingling. Could it be B12? I can check the F14 and 13 chips too.

Edit: forgot I already tried reseating f13 and f14 (and several other nearby LS chips) with no success.

Edited by ubersaurus, Sat Dec 29, 2018 6:46 PM.


#7 ubersaurus OFFLINE  

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Posted Sat Dec 29, 2018 8:41 PM

Good news! I reseated B12, H14, and F14 (again). Apparently one of them was the culprit, because now the thing is working right again! Thanks all for your help.



#8 Lee Adamson OFFLINE  

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Posted Sat Dec 29, 2018 9:28 PM

Glad you got it working!  :D



#9 Keatah OFFLINE  

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Posted Sat Dec 29, 2018 11:49 PM

For The Win!!





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