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WydD

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Hey everyone,

Lately I've worked on the CAT702 security chip on ZN systems in order to perform a ZN2 conversion (EX2 -> Tetris TGM). And today I've managed to succeed.
This is a picture of my current ultra-janky-af-breadboard implementation and a proof that the game is actually running in the original hardware.
EtE5_b2WMAAhsaA?format=jpg&name=small.jpg
EtE5_b7XAAY0Qav?format=jpg&name=small.jpg


Here's what I had to deal with:
  • Write the roms (duh)
    • Fortunately, this games uses only 32Mbit roms which are compatible with 27c322 chips. I'm able to write them using the arduino project I created a while back to write cps2 roms check it out here
    • If you want to burn EX2 / Strider 2 / Star Gladiator 2 / Tech Romancer, you might need to deal with 64Mbit DIP42 roms which are really rare afaik
  • Deal with the jumpers
    • Thanks to the works of @twistedsymphony, everything has been listed previously in this google doc. Thanks a lot!
    • Note: those jumpers in the end select if you want to transmit A21 address line to pin 11 (usually it's the /CS line). This line is useful only if you have a 64Mb roms which is okay here so we need to pull this to low here.
  • Recreate the PAL
    • Everything has been dumped and tested by @Hammy and @twistedsymphony so I was able to recreate BANK02 using a standard ATF16V8. Thank you guys!
  • Recreate the CAT702 for CP11 instead of CP08
The last one was more tricky obviously. The software implementation is available in MAME but it said that it must be able to support 2Mhz operations which is complicated on the software side.
So I recreated the algorithm in FPGA. It took me quite a while to have an operation which was perfectly accurate. After, spending some time setting up random inputs sent to the actual chip and a bunch of simulation, I was able to recreate a 100% accurate implementation using a TinyFPGA A1.

So, what's next? I know that @Hammy spent a lot of time on the ZN system. And with everything collected I think it opens up the way to multi ZN2 (maybe ZN1, not sure) without BIOS/ROM hacks. If you want to do such things, DM me so I can share the project with you.

For fun, I also have worked on a PCB to make this with proper dipswitches to select which key you want (it requires a MachXO2 1200 or TinyFPGA A2 otherwise you don't have enough space in the FPGA).
1612124229614.png

However, please note that I don't produce PCB professionally, I have no plan on producing it and shipping it to people.
But, if someone interested in this want to do it, I'd be glad to share the WIP design and the FPGA code. Please DM me here or through my twitter.

Enjoy!
 

ekorz

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You already @‘d the folks I’d think could help, so I’ll just say nice work! I love all the progress on these PS based systems. Can’t wait to shrink my actual pcb collection down to just a few of these boards.
 

twistedsymphony

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Dude, excellent work!

this is really ideal as it allow you to run the original unmodified ROMs!
 

Velyks

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Sick work! Better get some more ZN2 boards before the price goes up.
 

Hammy

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Impressive but it's the dreams of 2 years ago , now it's not really needed... I went the total opposite and eliminated the CAT totally.

View: https://youtu.be/8zRuUKdBh_o


All that's encrypted is the bios and boot vectors so it's no big deal, the mod bios way is better as it unlocks the motherboard for any manufacturer too ;)
 

WydD

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@Hammy yep I know, it's really impressive btw :)
I just thought it would be a nice project to try this way and provide an alternative way to enable other multi designs. ^^
 

Hammy

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Are you any good at hard disk controllers ? :D

PS : The mod bios works with the CAT if desired that would be a funny setup, i cut it from the current designs but will throw a socket on there in future if anyone wants that feature.
 

WydD

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Ermm nope, I never touched a hard disk controller, why do you ask :D
 

Hammy

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The blocks for me at the moment are:
Aero fighters fixedroms <needs gal dump>
NBA with it's batman forever soundboard
The remaining are all hard disk based ;)
 

ic3b4ll

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The blocks for me at the moment are:
Aero fighters fixedroms <needs gal dump>
NBA with it's batman forever soundboard
The remaining are all hard disk based ;)
I've been looking at the Batman Forever soundboard and right now I feel confident I could make a replica. The DSPs are available as either new parts or NOS/reclaimed chips.
I would need your help because there's a Mach111 and I don't have the tools to dump the thing. It could probably be replaced for newer parts.
On the STV I could adapt the riser I've been working on since forever to add the needed address/data lines.
I don't know what would be needed for the Zn systems but I don't expect major interface differences.
Want to combine efforts and make people happy? :)
 

Hammy

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I've been looking at the Batman Forever soundboard and right now I feel confident I could make a replica. The DSPs are available as either new parts or NOS/reclaimed chips.
I would need your help because there's a Mach111 and I don't have the tools to dump the thing. It could probably be replaced for newer parts.
On the STV I could adapt the riser I've been working on since forever to add the needed address/data lines.
I don't know what would be needed for the Zn systems but I don't expect major interface differences.
Want to combine efforts and make people happy? :)

Sadly i cannot dump Mach's or the lattice square CPLD's, The people who can dump them results are hit and miss..
This is a worthy project now both games need it, do you have the board(s) available?
 

stj

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has anybody tried to dump the pld's from the midway Y boards?
 

twistedsymphony

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Thank you for doing that. I think makes for a great way to revive a board with a dead cat702, and could help lead to different discoveries on this hardware
 

Hammy

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Nice to see it released! I will put a spot for it on any future rom boards should anyone wish to dabble with it and encrypted software :)

One note regarding "dead cat702's" If you get to or further than the green band on the bios screen both CAT chips will be ok, infact it's rare they fail more often just missing / wrong or noob damaged!
 
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