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NES 50/60Hz

Started by phreak97, January 13, 2004, 04:07:04 PM

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i am unfortunately stuck with a pal nes. can i make it do 60hz instead of 50?


apparently not...........

ill need to get me a us nes... or maybe i might even find a famicom @_@ that would 0wn, do they have a lockout chip?


When I did the all-region 'mod' to mine, I saw that Super Mario Bros ran noticable faster. I'm not sure if it was just an illusion or what but anyway... I think it was still running in PALvision, but played faster.
Open up, and lift pin 4 of the CIC chip. See if that gets you anywhere. If it doesn't, at least you have an all-region NES to play with.


i already broke pin for a week or so ago :P i dont think it made a difference

i mean, it plays imports now tho, and it doesnt blink when theres no cart but i didnt notice a change in speed


I don't think a 50/60Hz switch is possible on a real NES, but it is possible on some of the famicon/NES clones...  You know those ones shaped like Megadrives, N64s, Playstations, etc.  

I found a block of jumper pads on one that I had.   One set of pads selected 50/60Hz, another selected the number of built-in "games" shown on the startup menu, yet more I never worked out.  

Unfortunately I managed to kill the console while trying to fix a dodgey controller port.  For some reason they decided to build it on 3 seperate small PCBs connected via really brittle ribbon cables with paper insulation.  I was attempting to replace it with bettter ribbon cable when I must have shorted something.  :(

Cyber Axe

what about if one was to take the cpu out of a us nes and place it in a pal nes and use a switch to switch between them or sometihng along those lines?


NTSC NES CPUs run on a 21mhz master clock. (NTSC color carrier clock 6 times)
PAL NES if I am not mistaken runs on 17mhz   (PAL B/G/H/I color carrier clock 4 times)

That alone makes it complicated. The PPU is different because it has different video timmings and require a different clock frequency.
And the CPU is made to run at 17mhz too, so it won't work. Putting a PAL CPU on a NTSC NES will give you a high frequency sound and overclocked CPU/games crashing.  I've tried it myself. Trust me it ain't nice XD.

Btw sorry on the late reply but I just noticed this topic


lol.. i've had an ntsc nes for about three years now:P this topic is so old.. i've learned incredibly huge amounts since i posted that.

by the way cutting pin 4 does absolutely nothing to the gameplay speed. all the cic controls is the power state of the console.

theres gotta be a way to do it though, even if it means jamming most of the guts of two consoles into one casing. could you install two sets of cpu, ppu, and clock, then have a switch to choose which ones to use?


No, it doesn't control the power state of the console. It just "flashes" the reset line if a game has no CIC.

It's just that the POWER LED happens to be controlled by the RESET signal. That's why the POWER led goes off when you press the RESET button.

Cutting the pin 4 of the CIC chip inside the console causes it to feedback it's own outputs, causing it to no longer check for a CIC on the cartridge.
(well you know this I'm posting just for information, should others browse through this thread)

Oh and about the PAL nes in truth it doesn't run at 17.734476... In truth it does run at 26.601714 (4.433619 x 6) and in the case of the SNES they use a 17.734476 crystal and a prescaler/pll device to adjust the frequency to PAL color carrier x6.  I bet the PAL NES instead use an actual 26mhz crystal instead. (I've never seen a original PAL NES but I have a PAL CPU/PPU/Crystal  combo from some famiclone I converted to NTSC)

And let's keep the information flowing :D


youre right, i was thinking it controls whether the console is running or not, and thats how it came out.


I have 2 questions about NES console:

1. If I have a modded PAL NES and play a NTSC game, the game will work at 50 or 60 Hz ?
2. If I have a modded NTSC NES and play a PAL game, the game will work at 50 or 60 Hz ?


Because the PPU is what sets the Horizontal refresh, using an PAL NES will result on the game running on 50HZ regardless of it's region.

And boy some games get pretty unplayable due to frequency optimizations.
I'd suggest for you keep an NTSC system and a PAL system if you are in a PAL region.
If you are at a NTSC region, I'd avoid PAL cartridges and systems...

Unless you want them badly then, get a PAL system for them.


Ok, I understand your answer for the first question. But the second question ?

2. If I have a modded NTSC NES and play a PAL game, the game will work at 50 or 60 Hz ?


It works both ways. So you will get an PAL game working on NTSC frequencies. Which is pretty much glitchy.
That's why I say to keep away from PAL cartridges if you are on a NTSC region.


I've modded my PAL NES, cut the pin 4(not entirely). Some people says is better to attach a wire from pin 4 to pin 11,12,13,14,15 (ground) or place a switch instead.

1. What is the explication about wiring pin 4 to the ground?
2. What is the best method?


Nobody can help me with some answers  :'(?


you can just cut pin 4 off at the pcb and lift it a little to make sure it doesnt make contact. you can just leave it lifted, I've never seen it cause any problems being left that way.


Hey, I'm new to these forums, and a little new to modding in general, and aware this thread is old, but (to me) it is the most logical place to put this post.
In relation to the NES 50/60Hz mod (also noting this thread and associated info: ) I am picking up where Phreak97 left off.

Quote from: phreak97 on September 17, 2008, 09:47:44 PM
theres gotta be a way to do it though, even if it means jamming most of the guts of two consoles into one casing. could you install two sets of cpu, ppu, and clock, then have a switch to choose which ones to use?

I have a PAL NES, and the following info:
PAL NES runs a 26.601712MHz crystal with the 2A07 CPU (2C07 PPU) using a 16x divider (1.66MHz CPU speed)
NTSC NES runs a 21.47727MHz crystal with the 2A03 CPU (2C02 PPU) using a 12x divider (1.79MHz CPU speed)

The PAL/NTSC CPU's have DIFFERENT audio hardware in them, therefore, if the CPU ran at the correct speed, the sound would be wrong.
This results in the requirement to have BOTH CPUs installed. I have piggybacked the CPUs together, leaving /RESET selectable (one CPU running at a time).

Running the NES this way, i have found the following combos of CPU/PPU/XTAL to do the following:
2A07/2C07/26MHz: this results in normal PAL functionality/video/sound.
2A07/2C07/21MHz: this results in slower than normal sound (and video). The system is responsive, but slower, and the video is no longer syncable on a PAL/NTSC TV.
2A03/2C07/26MHz: this results in a no-go situation. No sound, no operation, but a stable, synced white screen.
2A03/2C07/21MHz: this results in a no-go situation. Maybe 1-in-100 power-cycles the system runs with no syncable video, and sound of unknown speed (haven't been able to time it properly to find out).

Looking at the schematic the power/reset/LED connector section/pinout is incorrect. This will be important to know if messing with the CIC for an auto-switch version of this.
Alongside that, it isn't exactly clear to me as to how the oscillator for the NES works; there are like 3-5 clock inputs to the PPU, alongside the lock in/out of the CPU. MAYBE a dual-oscillator could be used to run the PPU at a different speed (to the rest of the system) to get in sync with the CPU (reason the 2A03/2C07 don't like to talk to each other?), but in doing that, it's video-out (colourburst, etc) will likely be all screwed up.

So, the above testing/info shows that... the addition of an NTSC PPU (2C02/2C03) will likely result in a dual-region system.

I'd love to test this theory, but i have no cheap/easy source for the 2C02/2C03. (I can't justify the cost of an entire playchoice PCB hoping that the PPU is PRESENT, let alone if it will work in the PAL NES.)

As soon as i get my hands on a 2C02/2C03 (if anyone has a spare lying around, PLEASE PM me), i'll have a go at combining it all, and adding support for auto-switch, like Phreak97 has done with the SNES (using the CIC against itself)


MS1 and I are kindof working on this together.. with him doing all the actual hardware work due to me having not enough time/too much laziness.

as MS1 has said above,
our biggest problem now is that we dont have an ntsc ppu.. it'd be great if anyone could donate or cheaply sell us something with one in it (ntsc nes stripped down to the motherboard would be ideal, a playchoice pcb would also be acceptable at the right price, or even just the ppu itself as it's socketed on the playchoice.)

basically it looks like you can combine a pal nes and a nintendo playchoice or vs pcb and get a dual region console from it, we just need the ppu then you can expect a detailed schematic, since MS1 is much more familiar with schematic writing software than I ever have been.


lets say we have two problems.
problem 1:   ntsc colors/videooutput looks unacceptable
problem 2: rgb ppu wont give correct colors (or are there some by now?) = unacceptable

so we need both cpus with pal ppu to output pal50 and PAL60 signal, is that possible?
im ready to donate money if its possible


Thanks for taking an interest in this project, MrMikeCH. Regarding the potential problems though, we can...

Pair the 2A07 and 2C07 (PAL CPU/PPU), we will have a normal PAL output in 50Hz mode. (fine for PAL/auto-detect TV's)
Pair the 2A03 and 2C02 (NTSC CPU/PPU), we will have a normal NTSC output in 60Hz mode. (fine for NTSC/auto-detect TV's)


Pair the 2A07 and 2C07 (PAL CPU/PPU), we will have a normal PAL output in 50Hz mode. (fine for PAL/auto-detect TV's)
Pair the 2A03 and 2C03 (NTSC CPU, and RGB PPU), we will have an RGB output in 60Hz mode, BUT still PAL in 50Hz mode.

The 2C03 has an RGB output, but has (i think) about 2 or 3 colours that are not overly noticably different. The 2C04/2C05/etc are just not pallet-compatible.
But if we use the 2C02/2C07, MOST people thesedays will have a TV that supports both standards. (And it will be officially exactly the right colours if we use the 2C02 :P)

I believe we need two complimentary sets of CPU/PPU to achieve a switchable mod. But just now, i have read that there is a possibility my CPU is dead (i doubt it), as the 'correct PPU' supposedly can be used with either CPU.
I will look into this right now.


Hm ...  the PAL PPU will aways generate 50hz video. It's hardcoded on the chip.


OK, i have stumbled across Phreak97's old NTSC NES mainboard.
I spent yesterday carefully removing the CPU and GPU (now i have a genuine 2A03 and 2C02 (CPU/PPU).

My problem now is this: I need to know if the PPU (2C07 & 2C02) is able to be held in 'reset' by grounding the /SYNC line.
I can test this myself, but on a current-limited PSU, i get a current(limited) draw of 200mA at 3.3V... this looks bad, so i as wondering if anyone actually knows how much current one of these PPUs should draw (to know i'm safe to up the current).

Really want help, so i can keep this moving, as i finally found the time to work on it again :P


It's been a while, but I'm really curious if this project did get any update!


Hmm, well i just grabbed it out from under the bench, even though it's 4am, i should be sleeping :(
The result is... not good (i think why it went under the bench in the first place).

Each PPU appears to output a valid 'blank/grey screen' when there is no cartridge inserted.
When a PAL cartridge is inserted, the 'PAL mode' outputs reasonable garbage to the screen, but the sound is fine. In NTSC mode, there is nothing to see or hear (besides the blank/grey screen and whine of the CRT).
When an NTSC cartridge is inserted, the same happens, except in PAL mode, the sound is slower than normal (this is expected from NTSC in PAL mode).

Here is a video showing the results:

I wouldn't mind getting this going, but i am not sure how to proceed.
The bus switches i used to connect either of the PPUs in-circuit is a set of 2 CBT16210 per PPU. These have on-resistance of ~10ohms, and power/GND are permanently connected to both PPUs. This should be OK IMO.
The CPUs can be tri-stated, so they are run piggybacked except each /RES is controlled to run only one at a time.
The crystals are switched through a relay.
Only one set of CPU/PPU are active in either mode (after a power-up delay of 500-1000ms to catch the state of the CIC output for auto-detection of cartridge).

My thoughts on getting this going include the following:
Are the bus switches sufficient? - resistance should be OK. if there is a maximum bandwidth, that could be an issue...
Are the track lengths too long/crappy for the speeds involved (26MHz) - probably OK considering the rock-solid video and colour information (derived from the clock).
Is the N.O. contact of the relay OK? - i expect so as the 'blank/grey' looked OK, but i should check with my DMM.
Is the 2A03/2C02 alive? - i expect so, but i could swap them with another set.
Is the timing of the relay, PPU and CPU startup OK? - maybe there is a glitch, and they are not starting in sync? (they are not synced with the CIC reset line anymore...)
ANY further help/advice...

Sorry for the delay in all this. When i finally put it all together some months ago and it failed, i just wanted this project out of my sight. I really need to finish things i start...



I was thinking about a similar mod but with a nesrgb board since it can output rgb and support pal and ntsc ppu .
If i understood you keep both ppu powered at the same time and switch all other signals?
I wouldn't seem stupid but what would happen if you switch only vcc on cpu /ppu and xtal at the same time ?

( very interesting  search MeTrOiD_shift1 !  because as far as i know , no one is gone so far in that domain)

prince tomato

i realize this is a very old thread, but honestly there is not much else online at the moment regarding this exact issue.
i have exchanged the cpu, ppu and xtal from a pal nes with those of an ntsc nes, which works,
but i also thought it would be possible to "piggyback" the cpu and ppu and lift the 5v lines to hook up to a switch, and doing the same with one pin of each xtal.
doesn't work though, only solid white screen.
does anyone have any suggestions on how to use a pal chipset+xtal together with an ntsc set,
and how to switch between them?


Sorry to reply on a 17 year old post but i just cant resist. i solve the issue with high grade clone cpu and ppu, i used MG-P-501 CPU and TA-02NP PPU along side PAL 26.60 MHz Crystal, the pin 17 of PPU is Video mode select, 50Hz (GND) / 60Hz (5V), I choose MG-P-501 cause this CPU doesnt have reversed duty cycles bug, the setup runs perfectly fine, i tested 95% of the games with everdrive n8, works very much like origonal NES chips, maybe even better since it is PAL60 color at NTSC speed.


Maybe this will also work with an FPGA for CPU / PPU combo?
It would be great to see a 50/60hz actual NES console