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View topic - Battery save RAM added to non Save RAM cart??

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  • Joined: 27 Jun 2020
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Battery save RAM added to non Save RAM cart??
Post Posted: Fri Jul 02, 2021 12:50 pm
Hi guys,

Anyone have the info on adding a battery back up to a game like Afterburner or Golden Axe so that you could turn the cart into say, Phantasy Star?

If worse comes to worse I will go over monopoly with eyes / multimeter... just... ugh... so over... that...
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Post Posted: Fri Jul 02, 2021 1:10 pm
It requires mapper support so it’s probably easier to make a new PCB from scratch with your homebrew mapper rather than try to Frankenstein it onto an existing one.
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  • Joined: 27 Jun 2020
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Post Posted: Sat Jul 03, 2021 4:11 am
Hopefully someone comes up with a cheap throw on the board FPGA solution
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  • Joined: 04 Jul 2010
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Post Posted: Sat Jul 03, 2021 8:10 am
Cheap and FPGA on the same sentence... ^^
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  • Joined: 05 Nov 2014
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Post Posted: Wed Jul 07, 2021 7:39 am
Modding a monopoly or penguin land cart would be the quickest option. Youll need to add a few wires between the rom and mapper for the extra address lines due to needing a larger rom for phantasy star.

I brought a cheap copy of golfamania to see what was going on inside it, and it had an embedded mapper in the game rom, with extra pins to drive the sram, so thats not useful as a doner.
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  • Joined: 11 Mar 2018
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Post Posted: Wed Jul 07, 2021 11:36 pm
ichigobankai wrote
Cheap and FPGA on the same sentence... ^^


Not all FPGA/CPLD chips need to be powerful enough to fit a complete games console on them. More basic models with ~800 gates are around $5.
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  • Joined: 04 Jul 2010
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Post Posted: Thu Jul 08, 2021 6:56 am
I know as i'm using CPLD (32 to 128 macrocells) on my SMS boards.

Nowadays you can read "FPGA" everywhere... But CPLD are not FPGA.
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Post Posted: Thu Jul 08, 2021 7:05 pm
Most of the things that are currently sold as CPLDs are more like FPGAs than the CPLDs of a decade or two ago. (They have "fabric" and uniformly distributed individual bits of logic that you have to allocate routing resources between. Oldschool CPLDs are much more like PALs)
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Post Posted: Thu Jul 08, 2021 7:48 pm
PAL/GAL are SPLD, (nice) old tech for tiny/simple project, unfortunately no JTAG.

CPLD are more simple/light than FPGA
old EPM7032 or recent component like ATF1502 acts identical, but yes there are some big CPLD like MAX V or old MAX II series.
But even biggest are just like tiny baby FPGA (in size)
Changing manually functions/routing between logical bloc to fit things can be... complicated.

FPGA needs external rom for their configuration (so needs time to load and boot), internal structure is nowhere like a CPLD. Faster, bigger, for big project. You can't really use this in a cartridge due to their price, speciffically on SMS which have, unfortunately, a very low audience.
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Post Posted: Thu Jul 08, 2021 9:59 pm
Look at how the MAX V synthesis software works. It's just a small FPGA inside.

I recently was playing around with them recently; the 5M40 smallest tier is clearly just one of higher tiers where the synthesis program only lets you use 5 of the 25 "blocks" of fabric..

The iCE40 series of FPGAs have an OTP internal ROM, although most can boot from external SPI ROM too.

Anyway, right now commercially "CPLD" seems to mean "smaller FPGA with internal flash". But historically that wasn't the distinction, and that's why I make the distinction about whether there's "fabric" or not.
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