20/21-pin differences


Staff member
Let's try this again, shall we?

1 -> SH-1 Pin 79

2 -> Ground

3 -> SH-1 Pin 107

4 -> SH-1 Pin 108

5 -> SH-1 Pin 101

6 -> SH-1 Pin 111

7 -> SH-1 Pin 100

8 -> Ground

9 -> JP5 (?)

10 -> Ground

11 -> YGR-019B pin 124

12 -> YGR-019B pin 125

13 -> YGR-019B pin 126

14 -> Ground

15 -> YGR-019B pin 128

16 -> YGR-019B pin 129

17 -> YGR-019B pin 131

18 -> YGR-019B pin 130

19 -> Ground (also connected to something else through a resistor, not that it matters)

20 -> R47 (4.7KOhm), not sure where the other side of R47 goes ATM...
I'll have to see what I can find.

I was, ahem, relying on that post moving to the new board...

We should also look at which pins pass through and which are modified by the modboard, yeah?
Yeah, that would be a good idea. I haven't seen any modboard images good enough to make that out, though. I'd imagine that all the important stuff goes through the PAL/GAL... from that we should be able to determine the direction of each signal I think. I'll also see if I can figure out where stuff goes on my CD board; I already found that it uses a (standard IIRC) Hitachi H8 MCU, along with several semicustom chips. My guess is that the H8 actually manages the drive and presents a relatively abstract interface (SCSI-like or so) to the Saturn CD interface. If this is true, then the modboard is probably only modifying a small packet saying that the signature was/was not found, rather than inserting the signature data itself.
1 -> IC 20 315-5746 pin 7

2 -> Ground

3 -> SH-1 Pin 107

4 -> SH-1 Pin 108

5 -> SH-1 Pin 101

6 -> SH-1 Pin 100

7 -> SH-1 Pin 111

8 -> Ground

9 -> where R48 would be (dead end?)

10 -> YGR-019B pin 123

11 -> SH-1 Pin 79

12 -> Ground

13 -> YGR-019B pin 126 and 129

14 -> YGR-019B pin 125 and 131

15 -> YGR-019B pin 130

16 -> Ground

17 -> IC 39 VHC08 pin 2

18 -> YGR-019B pin 122

19 -> YGR-019B pin 118 via 300 Ohm R175

20 -> YGR-019B pin 128

21 -> YGR-019B pin 121

I might carefully have a look at my mod tonight.
would be nice to be able to make a 20/21 pin connector. That way we could use the 1st gen saturns. Made better imo.
I've had a bit of a look at the connections on my modboard.

It appears that the majority of them just pass through, but I still need to have a more thorough look.

I'll post some info soon.
I had a quick look at my CD board, but tracing the connections is a bit of a pain in the ass with a CD reader blocking the board...
Trying to trace things on my modboard is bending my brain...


Most of the pins pass through the modboard.

The ones that don't are 2, 3, 4 and 15.

1 passes through and goes to point 'B'

7 passes through and goes to one of the ICs.

I'll skip the unaffected ones.

Input (from CD board)

2 -> Pin 5 CF745-04

3 -> Pin 9 CF745-04

4 -> Pin 8 CF745-04

7 -> Pin 6 CF745-04 and pass through

15 -> Pin 12 74LS15

I haven't got to the output yet...but it could be academic anyway.

The pins that the mod address are mostly interchangable.

20 pin 21 pin

2 -> Ground 2 -> Ground

3 -> SH-1 Pin 107 3 -> SH-1 Pin 107

4 -> SH-1 Pin 108 4 -> SH-1 Pin 108

6 -> SH-1 Pin 111 6 -> SH-1 Pin 100

7 -> SH-1 Pin 100 7 -> SH-1 Pin 111

?? -> ? 15 ->YGR-019B pin 130

By connecting pins 2, 3, 4 and swapping pins 6 and 7 on a modboard, bypassing the other lines completely, that only leaves pin 15 unaccounted for.

YGR-019B pin 130.

ExCyber, could you try chasing up your pin 18 on your 20 pin main board? It's a long shot, and relies on my possibly flawed logic, but if that goes to YGR-019B pin 130, in theory a 21 pin mod might be able to be used in a 20 pin Saturn.

It would require plenty of hacking and be as fiddly as hell though...
That's so cool.

What do you think of the rest of the theory?

Are you going to give it a try?

I'm seriously considering buying a model 1 saturn and a modboard just to find out.
I think this is fairly promising, though there's still a chance that the logical protocol was altered between the 20-pin and 21-pin units. Also, we need to figure out where to grab an 8.467MHz clock signal (assuming that the mod really does need that exact frequency, which I kind of doubt).
Well, I know of the original Chinese mods which had everything built in (including timers/crystals ect). I think all the timing and logic was totally independent of the Saturn. It just "Knew" exactly what happened, at what time, so it could intercept data without interrupting the operation of the Saturn. The Chinese mods which Lik-Sang sells seems to use a timing wire (Rather than a crystal) to steal a pulse signal so it can synch with Saturn and do the above. The missing components doesn’t seem to be the only problem though, since im sure the logic must have changed because one Pin on the ribbon cable is not used anymore. Maybe they combined functions of that missing pin into another? Whatever it was, Im sure the logic had to be changed at least a bit to accommodate the 20/21 change.
I'd imagine that the CD interface itself is asynchonous (since these boards get a clock signal with a wire; if it was a synchonous interface one would think that a clock signal would be conveniently available at the ribbon connector), and the clock signal they chose was one that just happens to be available and drives the PIC at an appropriate speed. The PAL/GAL probably takes care of the basic timing.
I only thought about the signal wire after I logged out and started to think about the practicalities of hacking the mod in.

I agree it is possible that there has been a logic change between Saturn revisions (20/21 pin), but it seems quite a coincidence that the pins that my mod address are common to the 20 pin main board. Obviously the layout of the lines has changed a bit, but they are still there. Only by trying will we know.

I think that finding a clock signal source will be the hardest part. I have no idea how you would go about finding it on an existing component on the CD board, even though it most likely is there.

I've tried to track down an 'off the shelf' 8.467MHz crystal before, and drew a blank. I think people can make them for you, but I think you'd need a few thousand as a minimum order.

We could try substituting another crystal I guess. Soldering the 74HC04 on to the board wold be tricky though...
Its probably cheaper to just send your SS unit to HK. That, or get it modded at a Chinese store in your area which can do any version. Even just buying a new console is cheaper than trying to do a mod like that.
Yeah, but this is more of a challenge!

I tried looking for a video game store in Melbourne's China Town recently. I was just wandering through, but I couldn't see a single one...
Its probably cheaper to just send your SS unit to HK.

Actually, it probably isn't. Even assuming that there is a place that does it really cheap (is there? I've only seen places selling the modboards and premodded Saturns), postage to HK for anything bigger than a matchbox tends to be really bad.
I should be getting another mod soon (Thanks Curtis!

I'll then track down a model 1 Saturn. I'd laugh if it had 21 pins...
I'd offer to send you mine (well, technically it's my brother's, but he probably doesn't even remember that we have it
), but I bet the postage would cost more than a used Saturn... good old overseas shipping...
Originally posted by ExCyber@May 11 2002,03:28

I'd offer to send you mine


That's a little drastic. It'll be no problem to find one here. I found it harder to find a Model 2.