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Micro SD as a cheap cartridge alternative

  • Just thinking about different formats for delivering games on the MEGA65. Of course, there will be Paul's awesome 4 MB floppy format and it would be totally disrespectful not to ship floppy games with it given the amount of effort he's spending on it. However, for those who don't like floppies because they're slow or it's easy to lose one in a multi floppy set (for big games), I'm also trying to figure out a suitable cartridge replacement as those are expensive to manufacture and have very limited space (can't hold said multi-floppy big games). So I thought about this:


    Since the MEGA65 has the second Micro-SD slot which is automatically booted from if a Micro-SD is inserted in it, maybe Micro-SDs could be used as cheap big cartridge. One could realistically put custom versions of the OpenROMs sans BASIC interpreter that inject the game straight to the intended target address. Also a custom freezer that disable unwanted features like save states (no cheating). If I remember correctly, one of the nice things about this idea is that the OpenROMs allow raw reading of the Micro-SD card sector so one could also only do a minimal FAT32 partition that's only as big as required by CBDOS and Hyppo to boot the machine and load the main game PRG. The rest of the data could be put on a raw partition whose format is known only to the game.


    What do you all think of these ideas?

  • i like the idea !

    even if the MEGA65 itself is an open system, if a developer is producing games or other software for that machine, he surely could implement

    such security measurements to protect his work.

    But couldn't you just clone the SDcard ?

  • Yes you could but cloning to a byte level from an external OS requires a bit more technical know-how than just copying files. It's kind of like needing Maverick C64 with the crack disk to remove copy protections back in the day. Plus, it's more of a challenge as a real concern since the retro-computing scene is small enough nowadays that pirating new retro releases will get you a 💩 blast on every forum. Gone are the Commodore clubs of my youth with the trade/want lists.

  • ... maybe Micro-SDs could be used as cheap big cartridge.

    I didn't have a C64 module at hand, so for size comparison I used a module for the Atari 2600:



    You have "nothing in your hand" compared to the module with the microSD. It is alone in the haptics at all no comparison to the module.


    You grab a classic module with your whole hand and put it into the slot with a little pressure.


    A microSD card can almost be carefully inserted into the mini-slot with tweezers. And above all: How should a halfway collectible package for a microSD card look like? Together with a poster measuring 2cm x 1cm? :D

  • Honestly, I wouldn't buy several SD cards with games - maybe with a thumbnailed sticker on it?

    Then, just sell digital copies of your games.


    Guess, nowadays the retro fans are happy to buy their games, so they will also buy downloaded ones.

    Besides this, for collectors benefits you may plan real modules... but honestly don't know it the mega65 will have a cartridge slot... ??

  • Problem is cartridges have limited space. 128kb ain't much. I was thinking of something like a MEGA65 game with streaming FMVs. Certainly doable with a class 10 micro SD. With the size of the screen and using the RRB and a full character set and four palettes, that would come at about 5 MB/s uncompressed. Huge AAA games on a retro-computer 🙂

  • What is the reason the cartridge option is limited to 128kB?
    I like to use floppies for my own work, little programs and so on. Will probably also use the (internal) SD for that.
    When it comes to purchased games, for me nothing beats a real full size cartridge.


    Having said that, I fully understand the benefit of using microSD as substitute for a cartridge. The problem that I see is a microSD is soo small, and the SD slot is at the rear of the machine. Not really suitable for repeatedly inserting and swapping microSD’s.

    Personally I find the cartridge size used for the Nintendo Switch already at the very limit.


    But the future will tell us what option turns out to be the best one. I’m open to test all possible scenarios :)

  • Can't add to my own post so I'll add by double posting. There is also the fact that C64 cartridges only expose 16KB at a time and you have to add extra circuitry to do bank switching in your cart if you want more. Take a typical SSI Gold Box AD&D game which filled four to six floppies on both side discounting the extra Adventurer's Journal which contained all the text they couldn't fit in the game. To make a cart that would fit this kind of game would be very complex considering the limitations of having only 16KB of the cart memory mapped at a single time. Maybe if you can fit the PRG and common data in 8KB and say that the other 8 is a scratch loading buffer or other schemes like that.

  • I had to go look on Knights of Bytes website to validate that Sam's Journey was actually available on cartridge and not just on floppy but indeed it is (but only in PAL format). Gist of it: clever coding for the cartridge version and, if you go look at Protovision's website, the cartridge version is more expensive due to the additional hardware for bank switching. Knights of Bytes would be best placed to answer how they achieved that feat.

  • Sams Journey works out of the box as cartridge on the MEGA65 ;-)