Issues with Everdrive N8 and Blinking Light Win

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bngrybt
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Issues with Everdrive N8 and Blinking Light Win

Post by bngrybt »

Has anyone else ever experienced issues with an Everdrive combined with a Blinking Light Win?

I'm working on an MMC3 game. Been testing using my Everdrive mostly on a top loader and an AVS with no issues. I got a new CRT in my office and hooked up one of my backup consoles, a front loader with BLW installed. After playing for a short while I started getting really strange random feeling glitches and crashes, my character is teleporting around the screen, really strange stuff. Kind of feels like maybe there's an issue with bank switching being delayed or maybe random RAM values being corrupted. I'm not totally sure. Anyway, I have another unmodified front loader so I tried that and everything seemed fine.

I decide to move the BLW into the working system so I don't have to deal with the SD card catching against the side of the case when inserting it, but then the glitches followed to that system! I go back to the system that wasn't working properly to begin with. Played for a good half-hour or so and no issues whatsoever, so the problem is definitely the BLW.

Has anyone else experienced anything like this? Any reason why this is happening? Feels really oddly specific, but it definitely appears to be an issue.
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Memblers
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Re: Issues with Everdrive N8 and Blinking Light Win

Post by Memblers »

It sounds familiar, and doing a google search turns up similar reports.

My guess is the BLW connector added extra trace length or capacitance onto the signals. Carts like the Everdrive, using 74LVC logic and similar, will be affected differently than the usual hardware found on NES carts.
Fiskbit
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Re: Issues with Everdrive N8 and Blinking Light Win

Post by Fiskbit »

Is this an Everdrive N8 classic or Pro? Most frontloader consoles have a revision G PPU, which has an issue exacerbated by long traces where PPU OAM can corrupt. This issue frequently occurs with modern cartridge hardware, but very rarely with contemporary cartridges (except the FDS, where this is more common). This can be mitigated by adding 100 ohm resistors on the CPU data lines in series near the cartridge end.

The N8 Pro has these resistors built in. The N8 classic does not. These glitches could result in sprites glitching in all sorts of ways, though usually with some consistency per console. MMC3 IRQs could be affected in games using 8x16 sprites.
bngrybt
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Re: Issues with Everdrive N8 and Blinking Light Win

Post by bngrybt »

Fiskbit wrote: Sun Sep 04, 2022 9:17 pm Is this an Everdrive N8 classic or Pro? Most frontloader consoles have a revision G PPU, which has an issue exacerbated by long traces where PPU OAM can corrupt. This issue frequently occurs with modern cartridge hardware, but very rarely with contemporary cartridges (except the FDS, where this is more common). This can be mitigated by adding 100 ohm resistors on the CPU data lines in series near the cartridge end.

The N8 Pro has these resistors built in. The N8 classic does not. These glitches could result in sprites glitching in all sorts of ways, though usually with some consistency per console. MMC3 IRQs could be affected in games using 8x16 sprites.
It's the classic N8. I'm not exactly having PPU issues, but I am using 8x16 sprites and an MMC3 IRQ issue makes sense, so that probably explains it. I'll probably just avoid using the BLW while testing for now, but it's good to have an explanation as to what's going on.
bngrybt
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Joined: Tue May 09, 2017 5:03 am

Re: Issues with Everdrive N8 and Blinking Light Win

Post by bngrybt »

Just figured I'd post an update on this. I took Fiskbit's suggestion and added the 100 ohm resistors to the CPU data lines on the BLW and it absolutely fixed my problem. Figured I'd let people know in case anyone having the same issue refers to this in the future. Super easy mod, just added 8 resistors to the pins in back and cut the connecting traces in the front
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