Megaman X3 Project Zero

Discussion of hardware and software development for Super NES and Super Famicom.

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qwertymodo
Posts: 774
Joined: Mon Jul 02, 2012 7:46 am

Re: Megaman X3 Project Zero

Post by qwertymodo » Mon Jun 18, 2018 4:46 pm

I wonder if it might be possible to reduce the wiring by just disconnecting the high address line from the Cx4 and feeding that directly into the ROM chip (so the Cx4 thinks it's always within the 16Mbit memory space and doesn't tri-state the data lines).

zzattack
Posts: 14
Joined: Wed Oct 21, 2015 4:26 pm

Re: Megaman X3 Project Zero

Post by zzattack » Tue Jun 19, 2018 8:19 am

Haven't tried that but it did cross my mind. This was the easier theory to test, because of those data line test points. If that works, a 1-rom solution is easy too. If not, easiest way would probably be to design a custom board and transplant a cx4..

Ice Man
Posts: 526
Joined: Fri Jul 04, 2014 2:34 pm

Re: Megaman X3 Project Zero

Post by Ice Man » Sun Sep 08, 2019 7:41 am

Bumping that topic because I'm currently trying to make my own custom board for that hack.

While using 2x27C160 or 2x29F016 is a neat way and was already found working by zzattack I was thinking to only use one 27C322 for example.

Now my plan is:
Cx4 RD0-RD7 goes to 27C322 D0-D15 (using 2x 74HC257 to decode Lo and Hi)
Cx4 RA0 and /ROE are used to decode Lo and Hi via 74HC257.
Cx4 RA1-RA20 goes to 27C322 A0-A19.
27C322 A20 is controlled by the 74HC139 to switch between lower and upper 2MB of the ROM.

That way the Cx4 should always think it's within 16Mbit, right?

Frankym2612
Posts: 34
Joined: Thu Jun 27, 2019 8:25 pm

Re: Megaman X3 Project Zero

Post by Frankym2612 » Tue Oct 15, 2019 9:25 pm

Would it be possible to just run the last 8 data lines from a 16bit 32mb chip to the cx4? Like say using the original mmx3 cart Or does it absolutely need 2 roms

lidnariq
Posts: 9289
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: Megaman X3 Project Zero

Post by lidnariq » Tue Oct 15, 2019 9:37 pm

What is absolutely true:

The CX4 does not enable ROM in the $40-$7D and $C0-$FF banks. The Project Zero patch requires the ROM above the first 2MB be enabled in these memory regions.

It might be possible to trick the CX4 into enabling the ROM sometimes when it usually doesn't, by changing some of the address lines into it. Only if this is doable could it then possibly be true that a single 'PROM would be usable.

Frankym2612
Posts: 34
Joined: Thu Jun 27, 2019 8:25 pm

Re: Megaman X3 Project Zero

Post by Frankym2612 » Tue Oct 15, 2019 9:39 pm

Ok thank you!

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