Famicom - loading games and reset button.

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dq333
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Famicom - loading games and reset button.

Post by dq333 » Thu Feb 21, 2013 12:58 pm

Hello folks,

Bought an AV Famicom recently. I can load up one of my games, Punch Out perfectly, however other games don't load up instantly most of the time and just show up a blank screen. But, if I press reset the games work like 90% of the time. Even if the graphics are glitching, pressing reset fixes this. Is this considered normal? I am used to really inserting a game and seeing it either load up perfectly or with glitches ala NES, but seeing a blank screen a lot has me worried. I have never had to press reset with other old consoles to get games working. I have cleaned the game contacts with 90% isopropyl alcohol. I'm gonna clean the console slot tonight. I've heard that bootleg games require you to press reset to get them to work, but none of these games are pirate copies.

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rainwarrior
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Re: Famicom - loading games and reset button.

Post by rainwarrior » Thu Feb 21, 2013 1:41 pm

Maybe your Famicom has a a slightly glitchy power supply that doesn't settle fast enough? Once the power's already on, the conditions are more stable when you hit reset.

As far as bootleg games, the Famicom doesn't have a lockout device, so I don't think there should be a distinction for them like there is for NES.

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Re: Famicom - loading games and reset button.

Post by tepples » Thu Feb 21, 2013 1:50 pm

It might be that the bootleg games' mapper circuits are sketchier. I remember a video about Cheetahmen 2 in which someone quoted me about the Active mapper occasionally allowing the player to start the game in one of the levels past the unwinnable unfinished level. Should I go dig it up?

dq333
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Re: Famicom - loading games and reset button.

Post by dq333 » Fri Feb 22, 2013 7:22 am

Thanks for the replies guys. I used a brush on the slot and carts this time round and it works MUCH better. BTW, is a blue screen normal when there is no game or if the game cannot be read because of dirt?

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Re: Famicom - loading games and reset button.

Post by tepples » Fri Feb 22, 2013 8:05 am

If the PRG ROM cannot be read, the PPU will display one solid color. This is the same screen that alternates with black when no cartridge is inserted. Which color this is depends on accidents in manufacturing the PPU. I've seen an NES where it was gray and one where it was yellow.

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mikejmoffitt
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Re: Famicom - loading games and reset button.

Post by mikejmoffitt » Fri Feb 22, 2013 8:21 am

tepples wrote:If the PRG ROM cannot be read, the PPU will display one solid color. This is the same screen that alternates with black when no cartridge is inserted. Which color this is depends on accidents in manufacturing the PPU. I've seen an NES where it was gray and one where it was yellow.
Are there more details about this, I.e. what specifically causes it to choose a color? Further, if it is a result of an accident what else might be affected?

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Re: Famicom - loading games and reset button.

Post by tepples » Fri Feb 22, 2013 9:09 am

mikejmoffitt wrote:Are there more details about this, I.e. what specifically causes it to choose a color? Further, if it is a result of an accident what else might be affected?
A RAM cell is made of two inverters in a feedback loop, and an inverter is made of transistors, and a transistor is made of silicon doped with metals. If one inverter ends up very slightly stronger than the other, a flip-flop will power on in a state of 1; if the other, 0. The color you see is related to the value in the cells that correspond to the first palette entry when the NES first powers on. After the game successfully boots and overwrites this, nothing else will be affected.

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Re: Famicom - loading games and reset button.

Post by infiniteneslives » Fri Feb 22, 2013 1:33 pm

It's not so much as an accident as it's an inherent unique characteritic of your PPU due to the nature of semiconductor fabrication. My NES boots to blue screen when there's no cart also. Don't be concerned about that.

So did the issue clear up completely after cleaning the connector then?

I actually noticed a similar issue awhile back when running a FC game on my NES. It was actually 'F1 Race' for the famicom box, playing on my NTSC NES. The fact it was for the famicom box is irrelevant though, the ROM matches the normal FC version. IIRC the issue I saw was kinda the inverse of your problem. I was having issues where the game didn't like it when I hit reset. It would only boot properly at power up IIRC. I think it would lock up if I hit reset. I tested it out with a flash cart as well and found the same issue, so I concluded it was a 'bug' in the actual game, not handling reset properly for the NTSC NES in which it wasn't specifically designed for. I kinda ignored the issue at the time, but I now have a FC that I could test this out with and see what happens.
If you're gonna play the Game Boy, you gotta learn to play it right. -Kenny Rogers

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Re: Famicom - loading games and reset button.

Post by tepples » Fri Feb 22, 2013 1:44 pm

I thought the reset sequence of the Famicombox would be more like that of the NES given how both systems use the CIC.

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Re: Famicom - loading games and reset button.

Post by dq333 » Fri Feb 22, 2013 6:37 pm

infiniteneslives wrote:It's not so much as an accident as it's an inherent unique characteritic of your PPU due to the nature of semiconductor fabrication. My NES boots to blue screen when there's no cart also. Don't be concerned about that.

So did the issue clear up completely after cleaning the connector then?

I actually noticed a similar issue awhile back when running a FC game on my NES. It was actually 'F1 Race' for the famicom box, playing on my NTSC NES. The fact it was for the famicom box is irrelevant though, the ROM matches the normal FC version. IIRC the issue I saw was kinda the inverse of your problem. I was having issues where the game didn't like it when I hit reset. It would only boot properly at power up IIRC. I think it would lock up if I hit reset. I tested it out with a flash cart as well and found the same issue, so I concluded it was a 'bug' in the actual game, not handling reset properly for the NTSC NES in which it wasn't specifically designed for. I kinda ignored the issue at the time, but I now have a FC that I could test this out with and see what happens.
Yes the issue cleared up :D . A good clean does a lot.

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Re: Famicom - loading games and reset button.

Post by infiniteneslives » Fri Feb 22, 2013 9:26 pm

tepples wrote:I thought the reset sequence of the Famicombox would be more like that of the NES given how both systems use the CIC.
Either way the fact it was a FCB cart is irrelevant though because the rom was identical to the standard Famicom F1 Race release (based on checksum compare to bootgod's database anyways). So a 60pin F1 race using a 60 to 72 pin converter should give the same effect.
If you're gonna play the Game Boy, you gotta learn to play it right. -Kenny Rogers

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Re: Famicom - loading games and reset button.

Post by l_oliveira » Fri Mar 01, 2013 12:01 pm

I have a less interesting theory about this fault.

The FAMICOM has no reset control integrated circuit (unlike the NES) so it's RESET circuitry relies on a pull-up resistor, a electrolytic capacitor and a pressure switch.

What happens when you flip the power switch on is that the electrolytic capacitor need a certain time to charge itself up through the pull up resistor and while it's charging, the voltage is lower than the value a digital chip would consider as 1 so the reset signal is held low until the power stabilizes and the PPU is ready to receive writes. Since the capacitor in your system is old, there's a possibility that it failed already and the quantity of energy it's loading during it's charge isn't enough to keep the reset pin low through the required time.

Pushing reset after the power stabilized will cause the system to start correctly.

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Re: Famicom - loading games and reset button.

Post by Bregalad » Fri Mar 01, 2013 12:37 pm

I've seen an NES where it was gray and one where it was yellow.
It's funny because I also have seen two NESes where it was gray (likely $00) and one where it was yellow (likely $18).
You just make me notice that since my toploader NES has no connector issues, it never loaded a game improperly, and I don't even know its "default" colour ! I'll have to check it.
Pushing reset after the power stabilized will cause the system to start correctly.
Your theory is possible - but if what you explain is true, that would make the PPU being reseted longer than the CPU, the games would just hang in the initial $2002 polling loop until the PPU starts up correctly. Well at least I guess...

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Re: Famicom - loading games and reset button.

Post by l_oliveira » Fri Mar 01, 2013 12:45 pm

Bregalad wrote:
I've seen an NES where it was gray and one where it was yellow.
It's funny because I also have seen two NESes where it was gray (likely $00) and one where it was yellow (likely $18).
You just make me notice that since my toploader NES has no connector issues, it never loaded a game improperly, and I don't even know its "default" colour ! I'll have to check it.
Pushing reset after the power stabilized will cause the system to start correctly.
Your theory is possible - but if what you explain is true, that would make the PPU being reseted longer than the CPU, the games would just hang in the initial $2002 polling loop until the PPU starts up correctly. Well at least I guess...
The FAMICOM has the PPU "RESET" pin (we know now that it's not a RESET pin but a blanking sync control pin) tied to +5v while the old toaster NES had it wired together with the CPU RESET with the intent of making the screen blink along with the power led. By this I mean that the PPU may have nothing to do with this even though I mentioned it on the previous post.

If the CPU had not enough time to stabilize internally and RESET is set to 1 the result is unpredictable. The most likely thing to happen is it start up in a abnormal state which will prevent the execution of the game program.

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Re: Famicom - loading games and reset button.

Post by Pasky » Fri Mar 01, 2013 1:05 pm

I recall reading about this issue with the top loaders and the cause is the 1uF (I think it's 1uF) capacitor next to the reset switch. You power on the system, game won't load until you press the reset button. I'm not certain if the famicom top loaders share similar circuitry when it comes to the reset switch.

Try replacing that capacitor if it exists.

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