Blowing in carts to make them work

From a software point of view, what actually happens when the cartridge connector pins fail to connect properly? Is there a way to simulate the effect? Often the games seems to be somewhat playable, but with garbled graphics.

From the hardware viewpoint what happens is that some pins carry the wrong value (either permanently or for split seconds). From an emulation standpoint you'd basically have to emulate the relevant bits having incorrect values.

This is for the address lines and data lines by the way.

Point stands, some bits end up with the wrong values =P (either you get the wrong address or the wrong value from memory - just make sure you mess with individual bits rather than the whole thing)

It could kind of be simulated, but disconnected inputs on the hardware might be picking up any nearby electromagnetic field, so it's not going to look quite the same. Chris Covell once made a "Theremin" program based on this effect (the program loads into RAM, then you remove the cartridge). I can't find a link to it though.

Dirty connections on the CPU-space pins just cause the program to crash, or for the lockout protection to kick in, so that's not particularly interesting.

Dirty connections on the PPU-space pins are what's more iconic, and cause issues like split tiles, duplicated tiles, vertical lines and dashes, and all the wigglyness.

Also, you shouldn't actually blow in the cartridge. All you need to do is take it out and put it back in. If it's actually dirty, that's what alcohol water, isopropyl alcohol, and cotton swabs are for.

Edit: Don't use plain alcohol.

Not always, especially if the problematic part is an address line (in which case maybe it can access the area with the code just fine but not the area with the data).


Alcohol is too corrosive and damages the connections faster than blowing in the cartridge =P

Which solvent, then, is one supposed to use?

The manual for the NES Cleaning Kit recommended a mixture of water and isopropyl alcohol.

Sorry, I knew it was some kind of alcohol.

Woah!



Yep. Here is a less than scientific study on the topic.

It's unfortunate no one actually studied what precisely is happening to the pins when glitches occur. Is it just 1 pin causing the issue in general? When it happens, is it like a severed connection or does it work some percentage of the time and produce random bits or zero values or open bus otherwise?

Here are a few more glitch screen examples.

Generally, it looks like problems accessing CHR ROM.



Agreed. If there were problems with PRG ROM, in most cases, the game would not be playable. In fact, the processor would occasionally execute unofficial instructions. It would be interesting to see how a crash would manifest itself graphically.

As for the lockout chip, I assume that caused the cases where you hit power and it just kept resetting.

Nintendo must have noticed this issue during QA or at least during the first few weeks after the initial release. Why didn't they immediately step in and fix it? They could have even offered to repair existing machines that had the problem. It's really amazing that players of the day tolerated this kind of glitching. The reaction of players today would have been completely different.

Yeah, I'm curious as to why it's so difficult to get NES cartridges to work. I always have to wiggle the cart before it'll work correctly.

Maybe the problem is related to the zero-insertion-force cartridge connector? I know using a Game Genie (without any codes) was how my family solved this problem back then...

The ZIF slot is a big part of it. Nintendo added a ZIF slot to distance the NES in customers' minds from second-generation consoles sold prior to the North American video game recession of 1983-1984. I guess Nintendo wanted using the NES to feel more like using a VCR.

If a Game Genie works for you, the Blinking Light Win replacement slot should work even better.

It appears that when you push the cartridge down so it makes contact with the connector, it bends the connector pins a bit. As the connector gets deformed, making contact with it becomes harder and harder. A Game Genie is thicker than a regular cartridge, so it will make contact easier, but you'll be deforming the pins even more by using one.

Because it depends entirely on the situation. Just assume some line suddenly has a wrong value at least at some point in time.

I've heard this a lot but I don't think it is normally the actual problem. I think why people think so may be because after bending their pins it seems to work better because the pins make contact differently than before and cartridges that previously didn't work well now make contact on cleaner areas of the contact pins.

I've never had to bend any pins. If a game doesn't work reliably, cleaning it has always fixed the issue. Another reason I don't buy into this bending is people don't mention how SNES and Genesis games eventually experience similar issues and they certainly don't use ZIF connectors. And the solution for them once again is cleaning the games.

Maybe because the NES is the only one with that weird cartridge slot system, for the rest of the systems it's literally enough to just do a quick cleaning of the cartridge and the slot (if it refuses to work after than it means that either the cartridge is damaged or the board somehow got stuck too inside and needs to be pulled out to work).

I don't know the exact issues with the NES slot, but I imagine it's obviously going to be way more prone to other issues.

It's enough for the NES too if you clean the cartridges. It's possible like any other system that the connector itself has become damaged, extremely dirty, or corroded. I can only speak about my experience but cleaning generally fixes the issue. This whole bending pins is just a work around.