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PostPosted: Thu Aug 03, 2017 7:15 pm 
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Joined: Thu Aug 03, 2017 7:04 pm
Posts: 4
I'm not 100% sure if I'm posting this in the correct place but the issue I'm having is so specific & does have to do with how the NES is programmed I was hoping someone here would have the answer.
So I have this toploader I've been working on for awhile now. Pins needed a good cleaning & after that I would get an image but the background layer of sprites would be corruptted as you can see fro the pics I've attached. FOr example in Super Mario Bros Mario, Goombas & Mushrooms are fine but the actual background & bricks are not. I replaced the PPU, no change, the CPU, no change, the VRAM, no change, then I replaced the WRAM & the way the sprites were corrupted has changed. Now I'm using a roached NES board that I cannot rember what the original issue was. So maybe the WRAM in this was bad as well.
What I'm really asking, is the issue I'm having related to the WRAM or should I be lookign else where?


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PostPosted: Thu Aug 03, 2017 7:20 pm 
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PostPosted: Thu Aug 03, 2017 7:25 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
That definitely looks to me like the PPU's 2KiB of nametable RAM ("VRAM") is broken...

Since it repeats 4 times vertically, it might also involve the 74'373 latch ... but sprites seem to work correctly so I think that's less likely.


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PostPosted: Thu Aug 03, 2017 8:27 pm 
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Joined: Sun Sep 19, 2004 11:12 pm
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Location: NE Indiana, USA (NTSC)
Sprite display lists are in a completely separate area of memory from VRAM.


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PostPosted: Fri Aug 04, 2017 3:15 am 
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Joined: Sun Jun 12, 2011 12:06 pm
Posts: 217
Location: Poland
Please check if there is proper connection at following pins:
CIRAM A10
CIRAM !CE
PPU !A13

There might be also issude with other PPU address lines.


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PostPosted: Mon Aug 14, 2017 2:08 pm 
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Joined: Thu Aug 03, 2017 7:04 pm
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Update, It works! It was the VRAM, thanks lidnariq. Guess the VRAM I replaced the first time was faulty as well, third time's the charm.


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