SNES modding trouble

[Johan_H]

I want to perform the 50/60hz switch modification on my PAL SNES as described in the tutorial found here. (this is a shorter version for the more experienced.)
It says to "Locate the PPU1 and PPU2 chips. These are two of the largest chips on the board, so you should find them easily. They are in front of the game pak connector. PPU2 is nearest the connector, and PPU1 is in front of PPU2."

They are easy to find in these pictures referred to in the tutorial, but on my SNES, which looks like this, I can't find them.
I can see that they are marked U2 and U3 in the first picture, and I can find chips marked U2 and U3 on mine, but they don't even have the same number of pins.

Does this mean that it is impossible to install a 50/60 switch on my SNES, if not, can anyone tell me how to do it?

It should be noted that I'm a n00b with electronics and stuff like this, if you didn't notice already.

[creaothceann]

Try Google's image search with 'snes ppu1', maybe combined with '5C77' or '5C78'. Maybe it's under those other covers.

EDIT: Or maybe not. :/

[declan]

I know from personal experience that, nintendo made two revisions of the snes mother board (i have owned both versions).

In the first revision, the CPU(5A22), PPU1(5C77) & PPU2(5C78) were all separate IC packages.

In the second revision, the CPU, PPU1 & PPU2 were all in a single 160 pin IC package (RF5A122).

The mother board that you have photographed is of the second revision.

So, in short, the procedure shown in the tutorial here, is for the first revision of the snes mother board.

Now, i think its possible to mod your version, but the procedure is different of coarse.

Don't ask me what the procedure is, because i have no idea

can see that they are marked U2 and U3 in the first picture, and I can find chips marked U2 and U3 on mine, but they don't even have the same number of pins.

Looking at my "version 2" snes mother board, U2 is the APU all in one IC (in revsion 1, the APU, DSP & APU RAM were all seperate ICs).
And U3 is one of the CPU/PPU's RAM chips.

[Johan_H]

OK, so could it be possible that I just need to locate different pins?
Man, either my googleing sucks or there's not a lot of info on this floating around. It's probably just me not knowing what the hell to search for though, any tips?

[Gil_Hamilton]

I know from personal experience that, nintendo made two revisions of the snes mother board (i have owned both versions).

I think there's a lot more than 2 revisions.

But yeah.... trying to find the pins will be a pain without some documentation.

[declan]

I think there's a lot more than 2 revisions.

I didn't know that.

But i'm pretty sure there were only 2 CPU/PPUs layouts used.
The separate ICs for each processor and then the all in one IC package

Those other revisions, you speak of, must have changed thigns like, the design of the cart connector (i've actually seen two versions of the connector) and maybe changed the posision of a few ICs to make PCB design simpler or something like that.

[Gil_Hamilton]

I think there's a lot more than 2 revisions.

I didn't know that.

But i'm pretty sure there were only 2 CPU/PPUs layouts used.
The separate ICs for each processor and then the all in one IC package

Those other revisions, you speak of, must have changed thigns like, the design of the cart connector (i've actually seen two versions of the connector) and maybe changed the posision of a few ICs to make PCB design simpler or something like that.

I know they redesigned the SPC700 module at one point too.

And yeah, they only did 2 if you only score "1 chip VS discrete CPU/PPU1/PPU2" as variants. But different locations and orientations make it harder to sort out based on pictures.


I'm fairly sure there's more than 2 versions of the CPU and PPUs too, though they should all have similar pinouts.



You could probably take an ohm-meter and find the right traces. Not sure exactly where you'd probe, though.

[declan]

You could probably take an ohm-meter and find the right traces. Not sure exactly where you'd probe, though.

You'd have to get hold of revision 1 mother board and find were those pins (the 50Hz/60Hz pins that is) of the origional PPUs, went relitive to rest of the PCB (that is; where they connect to the RAMs, the resonators, the cart connector etc).
then you'd have to find the corresponding pins of the RF5A122, on your revision 2 mother board.

[Gil_Hamilton]

You could probably take an ohm-meter and find the right traces. Not sure exactly where you'd probe, though.

You'd have to get hold of revision 1 mother board and find were those pins (the 50Hz/60Hz pins that is) of the origional PPUs, went relitive to rest of the PCB (that is; where they connect to the RAMs, the resonators, the cart connector etc).

Unless you have, I don't know, a convenient text file that, in the process of detailing a project like, say, a region mod, explains that the pins in question are connected to, for example, +5V for PAL or ground for NTSC and nothing else.

then you'd have to find the corresponding pins of the RF5A122, on your revision 2 mother board.

It's not a rev2 motherboard. It's a, like, rev 6 motherboard or something.
Either way, you just have to find the pins shorted to +5V.

If the package was designed sensibly, and my thinking about chip design is correct, there is one power pin and one PALMODE pin. Good odds, and a poor chance of damaging the part if you guess wrong.

If it was NOT designed sensibly and my thinking holds, there could be 3 power pins and 2 PALMODE pins.

If my thinking is wrong, there could be many more than 2, or grounding the wrong one could kill something.

If the parts are distinct between US and Europe, then there's only one +5V pin, and it handles power and PALMODE, and you're screwed. I don't think this is the case, but it's just a hunch.

[declan]

then you'd have to find the corresponding pins of the RF5A122, on your revision 2 mother board.

It's not a rev2 motherboard. It's a, like, rev 6 motherboard or something.

No i only called it rev 2, because thats what i called it earlier.
I'm not doubting what you said Gil. Your a smart guy, i'm sure you know what your talking about.

[Johan_H]

What is a power pin?
So the way I understand it, I need an ohm-meter, find all pins shorted to 5V of the chip that says S-CPUN A, and pretty much guess which one(s) to use.

[creaothceann]

What is a power pin?

http://en.wikipedia.org/wiki/IC_power_supply_pin

[declan]

So the way I understand it, I need an ohm-meter, find all pins shorted to 5V of the chip that says S-CPUN A, and pretty much guess which one(s) to use.

You'd have to try shorting each of the pins, that are connected to the +5V rail, to the GND rail, and use a process of elimination to find the right one.

Wait! Just hang on a sec.

Now if i'm not mistaken, the pin your after, will have its logic status read (that is, test if the pin is high or low), every so often by program.
Therefore, if my theory is correct, the pin won't just be connceted to the +5V rail, it should be connected via a pullup resistor.
With this knowlege, it should narrow down the number of pins that need to be experimented with.

Also, nintendo went and put like brown mask over the bottom of the PCB, presumably to make reverse engineering harder. This makes following the tracks very difficult indeed. Thats were you multimeter comes in!
Strangly, i've only seen this brown mask on the PAL mother boards, my NTSC snes doesn't have it though. Thats not to say they never did though.

[Johan_H]

EXCITING UPDATE

I wrote and asked the author of the tutorials:

It's been a long time, but here's what I remember...

As far as I know, it's not possible to easily modify a late-version SNES
console like yours.

My guess is that there is one pin on the large S-CPUN chip that selects
the operating mode, but that this pin also changes the clock divisor.
(The clock crystal frequency is divided down inside the chip to get the
CPU clock frequency.)

That would mean that without replacing the clock crystal, the console
can't work in the "wrong" mode.

In theory it would be possible to fit a second clock crystal of the
correct frequency and switch between the two. However that would be much
trickier and more complicated than the relatively simple 50/60Hz
modification for older consoles.

Probably the simplest thing will be to buy a cheap used older-version
console, and modify that.

So, yeah. I'll buy an older version.

Thank yous to everyone who responded in this thread!

[Johan_H]

Eh, NECROBUMP

Is there any way one can tell which board revision a SNES has (or when it was made) without opening it? The seller might not always know this.

[declan]

No, i don't think there is a way of telling without opening it.

Though, the majority of consoles, will be the early version of MB.

If you do accidently get a later version snes, you can always sell it , and try again....

[Johan_H]

That's what I was afraid of. Eh, whatever, maybe I can even make an insignificant profit.

Though, the majority of consoles, will be the early version of MB.

Do you think you could guesstimate a rough percentage?

[declan]

I don't know if i could "guesstimate" acurately.

I could rattle off a figure, but just don't burn me at the stake if i'm wrong

I would think, you'd be looking 60% plus, of all snes's being version 1 MBs.

Look at it this way.... i've bought about 6 (go ahead a laugh) snes's, 5 of which are V1 MBs.... the only V2 MB i have, is the only one i got brand new, only months before the snes was dicontinued.

So you may have to buy a couple of snes's to find an appropriate one.

You have the nintendo security bit, don't you?
This will make your job alot easier.

P.S.
Don't use the melted plastic pen trick to open the console. Its a rubish way of doing it. Get the real tool.

[blackmyst]

Have you thought about just getting a pre-modded one on Ebay or something?

[Johan_H]

Have you thought about just getting a pre-modded one on Ebay or something?

I have, but they're not that frequent and usually ridiculously expensive compared to a regular one. Plus I have all the stuff necessary and I think it's a lot more fun trying to do it myself :)

Thanks for the info declan!



LATE EDIT: Not that anyone cares but: Success!! :D

[grinvader]

Don't use the melted plastic pen trick to open the console. Its a rubish way of doing it. Get the real tool.

Bah.

(molten)

Bah.