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PostPosted: Fri Jun 28, 2019 9:07 am 
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Joined: Thu Jun 27, 2019 8:25 pm
Posts: 22
Hi I recently made an add on board for laser invasion for sram (32k) and battery save and it’s not working I wired all traces from the ram to the ppu except we ce battery power vcc a13 and a14 to the mmc5 and it didn’t work I tried only on sim city the graphics are glitches up and it doesn’t save any idea where I went wrong?


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PostPosted: Fri Jun 28, 2019 10:14 am 
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Joined: Mon Jan 23, 2012 11:27 pm
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Sim city expects 2 ram slots of 16K each, not a single 32K. Each slot is capable of 32K on its own so I'd suspect you have your single chip wired up wrong.


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PostPosted: Fri Jun 28, 2019 10:22 am 
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Ah I was thinking it may be something like that as I tried sim city in a famicom cart with two 8k and it worked hm any idea how to wire that? I may try to add jumpers or something I really wanted this to be an add on for any big mmc5 repro game like legend of link


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PostPosted: Fri Jun 28, 2019 10:39 am 
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Here’s how I wired it: pin 1-pin 70 mmc5(a14) pin 2-pin 4 prg pin 3- pin 5 prg pin 4- pin 6 prg pin 5- pin 7 prg etc. pin 14 an 22 (oe) ground.

Pin 28 to 56 mmc5(vcc)
Pin 57 mmc5 to battery positive through 1k resistor
Pin 71 mmc5 to pin 20 ram (ce)
Pin 69 mmc5 to pin 26 ram (a13)
Pin 76 to 27 ram (we)


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PostPosted: Fri Jun 28, 2019 7:59 pm 
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May have found out the problem will check tomorrow I really want to get this going because the fit is great it will make for a clean add on to use a us full size cart for legend of link/ megaman/ any repro that needs mmc5


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PostPosted: Sat Jun 29, 2019 7:53 am 
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Joined: Thu Jun 27, 2019 8:25 pm
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So I tried the fix: it was just I had traces not fully soldered but that didn’t help except that now on the pick map it’s all actual solid blocks before it was little pieces of blocks. The loading screen is fine but when starting a new town it’s all garbled. It did this when I just had the chips in board with no adapter so does this game mess up without sram? So am I leaving an address out or I don’t know any help with figuring this out would be appreciated I’m stumped here are some pics:


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PostPosted: Sat Jun 29, 2019 12:41 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
SimCity specifically requires 2 x 8KiB of RAM. If you're using a single 32 KiB RAM, you'll need to hook it up to pins 75 and 93. Otherwise you get some issues.


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PostPosted: Sat Jun 29, 2019 12:56 pm 
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Joined: Thu Jun 27, 2019 8:25 pm
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Ok thanks! So 75 and 93 go to where on the sram?


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PostPosted: Sat Jun 29, 2019 5:23 pm 
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Well I connected 20 of the ram to 75 and it’s almost there the map shows well with just s row of corruption on top and it’s slmost playable but still won’t save. I just need to know where to wire 93 to


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PostPosted: Sat Jun 29, 2019 5:57 pm 
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Well I have pin 20 (ce) of ram connected to 75 of mmc5(ce 1 and 2) and I tied a15 from the mmc5 high by wiring to the battery plus(too many wires to go anywhere else right now lol) and it works! BUT....doesn’t do the main thing I want it to do, save. So I’m wondering where I went wrong there I feel I’m almost there the game now works perfect just doesn’t save the whole reason for this adapter


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PostPosted: Sun Jun 30, 2019 9:56 am 
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Another strange thing to note: I tried various 5v points to use for pin 93 and the only one that works is if I wore straight to the battery positive anywhere else and the game glitches i don’t understand what’s going on


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PostPosted: Sun Jun 30, 2019 2:45 pm 
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Joined: Thu Jun 27, 2019 8:25 pm
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Please can someone tell me where to wire these signals? I tried every possible combo with 75 and 93 lidnariq you told me which signals but then left me hanging


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PostPosted: Sun Jun 30, 2019 2:55 pm 
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Joined: Sun Apr 13, 2008 11:12 am
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Location: Seattle
I'm sorry, I just don't have the wherewithal right now to explain why, and I refuse to give answers without making sure they understand why first.

SimCity was made to run on ETROM, which has two RAMs. Without understanding more about how 1980s digital logic works, you should give up on trying to make it work with one RAM.


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PostPosted: Sun Jun 30, 2019 3:02 pm 
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I have it working just need to know where to add these wires I have ce from the ram to t75 I know that’s right I just need 93 it seems tying it high it works I w don’t know your issue with further helping I’m NOT giving up till I succeed!


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PostPosted: Sun Jun 30, 2019 3:06 pm 
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Joined: Thu Jun 27, 2019 8:25 pm
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I will get this working so I can give people the option of using this instead of ruining an expensive koe cart with or without your help


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