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PostPosted: Thu Sep 27, 2012 10:02 am 
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I apologize if this has already been covered elsewhere, but when I searched for this I couldn't find information on it anywhere. Now at one point in my life I was a hardware electronics engineer so when I read about the difference between lorom and hirom games I suspected that the difference's on the PCB's were only at the wiring on the mad-1 chip. Upon closer inspection of two of my games, Chrono Trigger, a hirom game, and NBA live 96, a lorom game, I found that the only differences with the PCB was indeed some of the routing of the mad-1.


My beloved Chrono Trigger PCB is below:

Image


Now below is the PCB of NBA Live 96:

Image


After a quick overview in Photoshop I'm willing to bet that a quick rewire of these 4 pin assignments would allow me to install a hirom game image on this lorom cart. My question is has anyone tried this before, and if so were they successful?


Last edited by Ren01 on Thu Sep 27, 2012 4:54 pm, edited 1 time in total.

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PostPosted: Thu Sep 27, 2012 10:52 am 
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So I picked out NBA live 96 because it has both a backup battery and 64k of sram. I'm planning the following to convert the PCB over:

I'm planning to rewire the assignments on the top of the pcb at the mad1's IC's legs as much as possible using the following four steps:
1) Navy blue pin to red pin assignment
2) Purple pin to to light blue(1) cut bottom trace leading to lower via
3) Red pin assignment to purple
4) light blue pin wire soldered to lower light blue(2) via only <-- possibly on the top of the pcb once I've removed the original mask rom for easy access

Anyone have any better more efficient wiring ideas?


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PostPosted: Thu Sep 27, 2012 4:40 pm 
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Location: Montréal, Canada
You can find plan for a crazy lorom/hirom switch over at romlaboratory's website. I'm sure you cna figure out what you're trying to do by looking at his info. That is if you don't mind getting a photosensitive seizure by visiting his site packed with animated gif from 2001.

Here's a link to save you from entering through his main menu: http://nintendoallstars.w.interia.pl/romlab/swlohi.htm

P.S: For the love of god, please resize your pic or link them up differently :shock: I'm not even kidding, I actually got blinded by your NBA JAM Scan :lol:


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PostPosted: Thu Sep 27, 2012 5:00 pm 
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SkinnyV wrote:
You can find plan for a crazy lorom/hirom switch over at romlaboratory's website. I'm sure you cna figure out what you're trying to do by looking at his info. That is if you don't mind getting a photosensitive seizure by visiting his site packed with animated gif from 2001.

Here's a link to save you from entering through his main menu: http://nintendoallstars.w.interia.pl/romlab/swlohi.htm

P.S: For the love of god, please resize your pic or link them up differently :shock: I'm not even kidding, I actually got blinded by your NBA JAM Scan :lol:


Thanks! Edited the photos for you :p I forget that not everyone has a super hi res screen all the time. Your link is promising in that it seems to be possible, but I have no rom replacements to test out my theory. I'm thinking of ordering from buyicnow.com, but I have a few concerns.

1) when you buy a tsop flash with adapter is everything soldered together for you as a drop in replacement?
2) I'm concerned about the longevity of the tsop flash retaining data. Does anyone have any idea?
3)Does anyone have any links for prepping the rom image for programming? I know you need to remove the header and I've used purify with bsnes to do so, but I want buyic to program the chip for me, and I'm not very familiar with the process at all.

Thanks!!!


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PostPosted: Thu Sep 27, 2012 10:12 pm 
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Location: Montréal, Canada
All the information you could ever need are already on this forum just a few thread down. Pre-soldered TSOP from buyitnow are drop in replacement for 36 pin MASKROM. As for the longevity, I wouldn't worry about this, I've seem eprom from the 80's still working so I do not worry much about flash memory. As for prepping image, snespurify from bsnes should be all you need.


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PostPosted: Fri Sep 28, 2012 8:34 am 
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SkinnyV wrote:
All the information you could ever need are already on this forum just a few thread down. Pre-soldered TSOP from buyitnow are drop in replacement for 36 pin MASKROM. As for the longevity, I wouldn't worry about this, I've seem eprom from the 80's still working so I do not worry much about flash memory. As for prepping image, snespurify from bsnes should be all you need.


Thanks SkinnyV! All your help is much appreciated. Hopefully in a few weeks I'll be able to report back that it was all successful. I do have a hirom madden 94 cart were I could solder off the maskrom and pop it in to the converted NBA live 96 pcb. Unfortunately madden 94 has no sram, battery or mad1 chip so I don't know if this will even work. Do you think it's worth a shot?


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PostPosted: Fri Sep 28, 2012 10:08 am 
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If the game didn't need SRAM, it probably won't hurt if it is on a board that has it. It's only when it needs it and doesn't have it that it is a problem. So you should be able to put the maskrom in the board that has the sram + battery. You're just wanting to test out if your LoROM/HiROM conversion works right? So borrowing the MaskROM should work.


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PostPosted: Fri Nov 16, 2012 7:29 pm 
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This is my idea for a Hi/LoROM switch:

Attachment:
1711201221.jpg
1711201221.jpg [ 104.93 KiB | Viewed 3440 times ]


I just used jumpers for now, it works. Later the switching will be done with two 4551 and a single on/on switch. In the future, I'll use a cheap MCU for reading out $FFD5 of the rom and auto switching to the appropriate setting.


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PostPosted: Thu Dec 13, 2012 12:10 am 
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Location: East Texas
Has this been tested yet? I could easily send you some mask roms (both Hi and Lo) or a tsop to dip converter.

Very curious if this works!


Did you re-wire the mask rom socket to a standard EPROM footprint?

I make an adapter circuit board that does that -- no hand re-wiring


Mark


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PostPosted: Thu Dec 13, 2012 2:14 pm 
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Markfrizb wrote:
Has this been tested yet? I could easily send you some mask roms (both Hi and Lo) or a tsop to dip converter.

Very curious if this works!


It works. It's a Hirom cart and I tested with Claymates (Hirom) and Lagoon (Lorom), both run perfectly.

Markfrizb wrote:
Did you re-wire the mask rom socket to a standard EPROM footprint?


Yes, it's wired for a 27C801/080.

Markfrizb wrote:
I make an adapter circuit board that does that -- no hand re-wiring


Mark


This is just a "Prototype" to test my theory. Someday I'll make my own PCBs when I'm done testing.


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PostPosted: Thu Dec 13, 2012 6:25 pm 
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So all you did was make a switch to bank those 4 points in the earlier posts? I am planning on making a cart myself. Maybe we could collaborate? I have a very good CAD person who designs my pcb's.

If nothing else, I'd love to see how you implemented the switch. With an i.c. I think you mentioned.

Mark


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PostPosted: Thu Dec 13, 2012 6:43 pm 
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Rather than 2x4551's you should be able to use one of these. No guarantees, haven't tried it myself, but it looks like it should work.


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PostPosted: Thu Dec 13, 2012 8:43 pm 
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Markfrizb wrote:
So all you did was make a switch to bank those 4 points in the earlier posts? I am planning on making a cart myself. Maybe we could collaborate? I have a very good CAD person who designs my pcb's.

If nothing else, I'd love to see how you implemented the switch. With an i.c. I think you mentioned.

Mark


No, I just switched some adress lines. All you have to do to get a Lorom game working on a Hirom cart is skip A15. As I said, this is just temporary, the next step is to programm a cheap PIC (or a FPGA should even be enough) to do auto switching.

Thanks for your offer, perhaps we can work together some day. At the moment I only need help programming a mailbox software for the SNES.

qwertymodo wrote:
Rather than 2x4551's you should be able to use one of these. No guarantees, haven't tried it myself, but it looks like it should work.


It's not going to work. This part has only one input and one output for every signal. There have to be two inputs and one output.


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PostPosted: Thu Dec 13, 2012 9:30 pm 
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Location: East Texas
Good to know. Thanks!


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PostPosted: Fri Dec 14, 2012 2:43 am 
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ngevan2k wrote:
qwertymodo wrote:
Rather than 2x4551's you should be able to use one of these. No guarantees, haven't tried it myself, but it looks like it should work.


It's not going to work. This part has only one input and one output for every signal. There have to be two inputs and one output.


Woops, you're right. You could do it with 1 of these and just tie the 2 output buses together, then use a single transistor NOT gate as a 1-of-2 decoder to drive the /OE's. Considering the alternatives, MAX4551's are ~$4 each and you'd need 2. A cheap PIC is going to be a couple bucks, and then you have to program it. An FPGA is complete overkill. The 74CBT16210 is ~$1.


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