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SNES game PCB cartridge with chip vs battery to save

Posted: Mon Jun 15, 2020 8:29 am
by Kayumba
Hi for all,

Can you explain me please, why there is no possibility to make PCB for SNES games with chip to save the game vs battery?
I can see here for example, that on ALiexpress, Chinese propose game version with battery and without:
Image

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Mon Jun 15, 2020 8:53 am
by Memblers
two possibilities I can think of:
1 - could use FRAM or similar non-volatile chip. not available much as a 5V part, and Sonic 3 for MD/Genesis was the only cart that I know that used FRAM.
2 - a game could save to the same flash memory that's holding the game. this requires (potentially) extensive changes to the game though, unless you do it like the PowerPak, where you must reset to the menu to save.

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Wed Jun 17, 2020 8:47 am
by Kayumba
Memblers wrote:
Mon Jun 15, 2020 8:53 am
two possibilities I can think of:
1 - could use FRAM or similar non-volatile chip. not available much as a 5V part, and Sonic 3 for MD/Genesis was the only cart that I know that used FRAM.
2 - a game could save to the same flash memory that's holding the game. this requires (potentially) extensive changes to the game though, unless you do it like the PowerPak, where you must reset to the menu to save.
So it's possible to use FRAM with custom PCB?
Why no body do it accept chines ?
See here:
Image

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Wed Jun 17, 2020 10:40 am
by lidnariq
Two reasons:

1- FRAM is drastically more expensive than SRAM and a battery and all the support hardware

2- Almost all of the available FRAM is 3V only, so you must include extra hardware in order to not damage it and/or your SNES.

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Thu Jun 18, 2020 7:36 pm
by Memblers
It often seems to be the case that Chinese bootleg carts are made with recycled parts (pulled from other boards). Like on FC multicart I bought, the flash chip still has a sticker from the original software in a pachinko machine. It also has a coin-cell holder, and the seller noted you can add your own battery. But the RAM chip being backed up is a recycled 71256 (fast cache RAM).. maybe the battery could last for some days or weeks? Plus it wipes your save when you run any other game that uses WRAM, it's just altogether janky. But incredibly cheap.

I see that picture shows a Ramtron part, that company no longer exists but I believe was bought by Fujitsu. I suppose it's possible they kept the Ramtron branding, I don't know, seems doubtful. Could be old stock or recycled.

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Fri Jun 19, 2020 10:17 am
by getafixx
Memblers wrote:
Thu Jun 18, 2020 7:36 pm
I see that picture shows a Ramtron part, that company no longer exists but I believe was bought by Fujitsu. I suppose it's possible they kept the Ramtron branding, I don't know, seems doubtful. Could be old stock or recycled.
They re-branded. Those chips are FM18W08 (or FM28V020 for 3.3V systems), by Cypress Semiconductor now.

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Sat Jun 20, 2020 1:04 am
by calima
FM18W08 unit price: qty 1 28$, qty 1000 19$. Yikes, the only way those chinese can afford to put them in snes repros if they can pull them for free from some junked equipment.

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Sat Jun 20, 2020 6:08 am
by aquasnake
recycled FRAM and Flash ROM

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Sat Jun 20, 2020 6:38 am
by aquasnake
calima wrote:
Sat Jun 20, 2020 1:04 am
FM18W08 unit price: qty 1 28$, qty 1000 19$. Yikes, the only way those chinese can afford to put them in snes repros if they can pull them for free from some junked equipment.
a part of cantonese did so:

a certain number of countries transported electronic junk to china,

a certain number of people disassembled them and picked up the fine components,

another certain number of people made some kind of electronic equipment and re-transported to a certain number of countries,

all happy, are we?

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Sat Jun 20, 2020 2:00 pm
by Markfrizb
calima wrote:
Sat Jun 20, 2020 1:04 am
FM18W08 unit price: qty 1 28$, qty 1000 19$. Yikes, the only way those chinese can afford to put them in snes repros if they can pull them for free from some junked equipment.
Mouser and Digikey sells them for $17 range... the 64k version is around $9....still too expensive.

How fast does a sram need to be though? Could sram be as slow as 130ns?

Re: SNES game PCB cartridge with chip vs battery to save

Posted: Sat Jun 20, 2020 2:19 pm
by lidnariq
Looking on Octopart, I'm seeing 3V FRAM from Rohm (MR48V256) and Fujitsu (MB85R256) for mediocre prices ($5/@1 down to $4/@1k).

SNES cart RAM is almost always in a SlowROM location, so /RD or /WR are asserted for 5 MCy≈230ns, so a 130ns memory should be fine.