Largest possible cartridge ROM size with SA-1?

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shedletsky
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Largest possible cartridge ROM size with SA-1?

Post by shedletsky »

Hello.

I'm creating an SNES game/piece of weird art and I want to produce 5-10 physical cartridges to give out as gifts to friends in the game industry.

I'm trying to figure out if I can afford to use SA-1 in my game, since it seems like all the possible SA-1 donor carts have a relatively small ROM size.

Has anyone been able to put a 6 or 8 MB ROM on a SA-1 cart? Wondering if it is as simple as soldering a larger ROM chip onto an SA-1 board.
lidnariq
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Re: Largest possible cartridge ROM size with SA-1?

Post by lidnariq »

On the one hand, FullSNES claims that the SA-1 theoretically has enough pins to address 16 MiB of ROM.

On the other hand, no existing PCB currently has all the needed traces for this.

Furthermore, you can't buy big programmable ROMs in the needed capacity and capable of operating at 5V, so you need to add some protection to keep from damaging the SA-1 and/or ROM, which makes the needed PCB area bigger.

If you're not already comfortable with a lot of surface mount soldering, I'd recommend planning on not using the SA-1.
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jeffythedragonslayer
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Re: Largest possible cartridge ROM size with SA-1?

Post by jeffythedragonslayer »

What's your budget for this project?
tsop48
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Re: Largest possible cartridge ROM size with SA-1?

Post by tsop48 »

MX26L6420 work with SA-1 , it have 8 mb , time ago i was thinking to make a multicart with games for this kind of board , but there is not enough games of my interest . Maybe a Super Mario RPG with KIRBY Super Star or Kirby DreamLand 3 , but need to change the S-Ram too.
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shedletsky
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Re: Largest possible cartridge ROM size with SA-1?

Post by shedletsky »

jeffythedragonslayer wrote: Wed Feb 15, 2023 10:48 pm What's your budget for this project?
One way that I've thought of accomplishing my goals was to buy a SD2SNES and somehow hardcode it to just load my game ROM instead of booting into its OS. No idea how possible this is - my understanding is that maybe the board design is open source. I just paid $400 for one of these to do development on. So conceptually that kind of sets the ceiling for me at around $400-500 for one cartridge.

If I could produce the first cartridge for $500 and then 9-14 more cartridges for $100, I'd be pretty happy. So I guess my budget is around $1500-2000.
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jeffythedragonslayer
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Re: Largest possible cartridge ROM size with SA-1?

Post by jeffythedragonslayer »

shedletsky wrote: Thu Feb 16, 2023 4:30 pm
jeffythedragonslayer wrote: Wed Feb 15, 2023 10:48 pm What's your budget for this project?
One way that I've thought of accomplishing my goals was to buy a SD2SNES and somehow hardcode it to just load my game ROM instead of booting into its OS. No idea how possible this is - my understanding is that maybe the board design is open source. I just paid $400 for one of these to do development on. So conceptually that kind of sets the ceiling for me at around $400-500 for one cartridge.

If I could produce the first cartridge for $500 and then 9-14 more cartridges for $100, I'd be pretty happy. So I guess my budget is around $1500-2000.
It it were me, I would just gift my friends a flashcart with my game already on it and not worry about reducing the flashcarts' capabilities. Who is going to complain about being given a free flashcart?
Markfrizb
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Re: Largest possible cartridge ROM size with SA-1?

Post by Markfrizb »

shedletsky wrote: Thu Feb 16, 2023 4:30 pm
jeffythedragonslayer wrote: Wed Feb 15, 2023 10:48 pm What's your budget for this project?
One way that I've thought of accomplishing my goals was to buy a SD2SNES and somehow hardcode it to just load my game ROM instead of booting into its OS. No idea how possible this is - my understanding is that maybe the board design is open source. I just paid $400 for one of these to do development on. So conceptually that kind of sets the ceiling for me at around $400-500 for one cartridge.

If I could produce the first cartridge for $500 and then 9-14 more cartridges for $100, I'd be pretty happy. So I guess my budget is around $1500-2000.
Hi
I’ve been down this road before and I have the pcb rom adapters you’d need already in hand. Max capacity of 8mB and properly down translated for the 3volt roms. Feel free to PM me for more information
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shedletsky
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Re: Largest possible cartridge ROM size with SA-1?

Post by shedletsky »

jeffythedragonslayer wrote: Wed Feb 15, 2023 10:48 pm It it were me, I would just gift my friends a flashcart with my game already on it and not worry about reducing the flashcarts' capabilities. Who is going to complain about being given a free flashcart?
That's rational, but we are creating art here.

The cool thing is that the game is a physical artifact you can plug into a 30 year old SNES and it works.
Markfrizb
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Re: Largest possible cartridge ROM size with SA-1?

Post by Markfrizb »

shedletsky wrote: Sat Feb 18, 2023 8:24 pm
jeffythedragonslayer wrote: Wed Feb 15, 2023 10:48 pm It it were me, I would just gift my friends a flashcart with my game already on it and not worry about reducing the flashcarts' capabilities. Who is going to complain about being given a free flashcart?
That's rational, but we are creating art here.

The cool thing is that the game is a physical artifact you can plug into a 30 year old SNES and it works.
Gifting a $200 flash cart for a single purpose, per person, seems expensive. A $10 donor cart + a small amount of work seems more reasonable financially (maybe $30-40 in total). And, when you plug it in and it’s on and works. To me, something gets lost when you’re confronted with a menu to navigate, at least of its art only.
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krzysiobal
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Re: Largest possible cartridge ROM size with SA-1?

Post by krzysiobal »

I have a free bare SNES pcbs that can be used for LOROM or HIROM, even with SRAM and battery backup.
Up to 8MB, with 5v->3.3v voltage shifters.
And USB cartridge burner. I can send you cheap if you wish.

BTW. What is SA-1 responsible for? Is it some kind of CPU with internal memory? I'm asking because I were going to make cheap SNES flashcart possible without any expansion chips, but I am wondering how many FPGA resources would be neccessary to simulate it.
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tepples
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Re: Largest possible cartridge ROM size with SA-1?

Post by tepples »

SA-1 ("Super Accelerator") is a 65816 CPU clocked at 10.74 MHz, 2 KiB of internal RAM, a CIC, and a memory controller. This memory controller arbitrates access to ROM and SRAM between the main CPU core (the 5A22 in the SNES) and the sub CPU core, switches banks in up to 8 MiB (64 Mbit) of ROM ("super MMC"), and can convert chunky pixels in SRAM to planar pixels for the S-PPU. Lacking specific experience, I suspect that the FPGA resources needed to emulate it would be on the same order of magnitude as those needed to emulate the SNES CPU (without the PPU or audio side).

Further reading: "SA-1" in Fullsnes
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shedletsky
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Re: Largest possible cartridge ROM size with SA-1?

Post by shedletsky »

Markfrizb wrote: Sun Feb 19, 2023 2:01 pm Gifting a $200 flash cart for a single purpose, per person, seems expensive. A $10 donor cart + a small amount of work seems more reasonable financially (maybe $30-40 in total). And, when you plug it in and it’s on and works. To me, something gets lost when you’re confronted with a menu to navigate, at least of its art only.
Yeah agree with that totally.
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