Chance of a RAM cart for homebrew?

Discussion in 'Sega Discussion' started by vexatious, Nov 10, 2014.

  1. vexatious

    vexatious Active Member

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    What are chances of a 32mbit ram cart being made for 32X/CD homebrewers? How hard would it be to make one with basic soldering skills? What if I wanted a 64megabyte cart? Would that be too big in a standard cartridge size (what if I wanted simm slots for EDO ram)? Would an Everdrive+SRAM+32mbit RAM combo cart be possible?

    I think the SegaCD/32X would be very nice with a RAM cart. Certainly wouldn't mind tackling a DOOM port, especially with source code available. I find the SegaCD/32X a very nice system considering CDrs are bootable without modchip, and it seems much easier this way compared to the Saturn and its dual VDP setup (32X only adds a simple framebuffer over genesis VDP). Only problem I see are emulators available. I don't know if any work with 32XCD games.
     
  2. retro

    retro Resigned from mod duty 15 March 2018

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    Moved to the Sega dev forum, as this has little to do with EverDrive (and Krikzz has his own forum now, anyway).

    The fact that you have to ask this (plus the other questions) makes the answer - extremely hard! You'd need a very good understanding of how all three systems work to understand how to do it... or if it's even possible.
     
  3. vexatious

    vexatious Active Member

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    Sorry about that. Everdrive seems like a great option TBH.
     
    Last edited: Nov 12, 2014
  4. vexatious

    vexatious Active Member

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    Bump

    After getting 2 year online associates college degree in computer networking thought I'd keep asking.

    It appears the genuine Sega mapper allows a full bankswitched 256meg (32 megabyte) memory space in 512kb chunks. Moreover, 32x can only access first 32megs of space and bank switching is only allowed from main 68k. This means only about 4.5 megabytes total of local buffer for CD programs-content (games); at least it's a little more than Saturn.

    Standard Everdrive only comes with 64meg but it seems like re-writable eeprom as opposed to RAM since description states 100,000 writes. Only the "Mega Everdrive" has infinite writes but doesn't clearly describe RAM or rewritable eeprom, and it's larger space.

    According to Sega SDK (assuming it's authentic), each SH2 has 2 dma channels into main 68k of genesis. Furthermore, SDK states this is implemented to allow access to memory space on SH2s (256kb + 256kb) from hardware on CD side. Sounds like the ASIC can draw into 15-bit color vdp directly if I'm guessing right. 68k sounds like a memory-system controller in addition to a CPU.

    Worst part about all this is testing support without a Mars 32x devkit. Doubt any emulator supports full Sega mapped 256meg space, let alone as RAM expansion for CD32x. Hopefully memory spaces are protected against coding error.


    EDIT:

    So far it seems easiest to find a broken "Super Street Fighter 2" cartridge and swap rom for ram (preferably socketed). But problem with this is lack of Sram and only 64megs seems possible.

    Seems humiliating to ask development questions in a forum mostly populated by hackers and hacks. Like walking into High School being preyed by bullies.

    Thanks
     
    Last edited: Mar 17, 2019

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