Megadrive emulation in a Dreamcast VMU

Discussion in 'General Sega Discussion' started by biggestsonicfan, Aug 4, 2019.

  1. biggestsonicfan

    biggestsonicfan

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    The main page is here.



    SMD_Koubou has manufactured a PCB that fits inside a Dreamcast's Visual Memory Unit and can play Megadrive games!
     
  2. Vangar

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    Welp, thats bizzare. Here's another video of it playing NES:

     
  3. biggestsonicfan

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    I want one... bad...
     
  4. Cooljerk

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    Thats pretty neat, but just to clarify, it's an entirely separate, more powerful piece of bespoke hardware that emulates a genesis that fits into a VMU shell, replacing the screen. Again, neat, but worth distinguishing.

    Worth distinguishing, because THIS is an actual ARM Cortex-M23 emulator for the VMU, as in it runs on the literal Sega Potato processor. This ARM Cortex emulator for the VMU is incredibly useful, because otherwise the only way to write code for the VMU is in pure LC86K VMU Assembler, no C to VMU toolchain exists. And unlike very forgiving consoles like the Megadrive or even the Dreamcast, VMU assembler is a nightmare. For example, its memory uses 9-bit addressing despite it being an 8-bit CPU, with the caveat that only certain registers can access certain areas of memory. On top of this, the Screen LED itself is split over two arrays in two different banks of memory making writing and drawing to the screen extremely difficult. This is the main reason why the VMU was so underused on the Dreamcast. Programming for the VMU is very complex, more complex than the Dreamcast. The VMU programming manual from Sega is literally thicker than the programming manual they provided for the Dreamcast with the Kitana SDK!

    The ARM Cortex M23 emulator for the VMU runs a very good speed, enough to actually develop real VMU applications. Most importantly, it lets people actually write VMU applications in C, compiled into ARM Cortex M23 code, running on the emulator ontop of the VMU. Added benefit is that the ARM emulator has normal addressing, a virtual normal contiguous memory block, etc.

    Example:

     
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  5. biggestsonicfan

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    If anyone couldn't distinguish it from looking at it, I suggest they get their eyes and head examined to be perfectly honest. In my first post, I mention that a special PCB has been made to fit inside a VMU. No one is trying to trick anyone into thinking a stock VMU was softmodded into this.
     
  6. Cooljerk

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    It's almost as though there was an entire paragraph following the sentence you quoted explaining why that distinction was pointed out or something (hint: it wasn't any allegation of tricks).
     
  7. grap3fruitman

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    It was distinguished and you're being pedantic just because.
     
  8. Cooljerk

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    It's not "pedantry" nor did I accuse OP of "tricking" anybody, it was distinguished to contribute to the topic. These annoying posts trying to claim nefarious intentions in my contributing post are far worse than what you consider "pedantry."
     
  9. grap3fruitman

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    Yes it was and yes you did. I'm not playing this game.
     
  10. Vangar

    Vangar

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    The fact that the screen is high resolution and in color should be enough for anyone to realise the original hardware is no longer inside. This kind of thing has been happening for quite a while now. I remember reading about this one a few years back:

    https://hackaday.com/2010/09/29/dreamcast-vmu-meet-ipod/
     
  11. doc eggfan

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    Are these going to be mass produced, or is it just a neat one-off.

    I would jump at the change to buy one, although an SMS/GG version would be better, considering the two button layout.

    Hell, a game boy emulator would be awesome too, considering the form factor. In fact, why hasn't nintendo done a game boy classic/mini yet?
     
  12. SoNick

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    While this is neat, I'm not sure how much I can get behind something that involves cannibalizing a VMU. The hardware's not rare now, but they are no longer being produced, so there is a finite supply of them.
     
  13. mentski

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    I'm not saying you're necessarily wrong, but when it comes to VMUs, coming up to 20 years on and there is still a WHOLE lotta old new stock hanging about for sale. I bought one new in box only this week, full working batteries with the tab in and all.

    The amount of people that'd undertake a project like this is a drop in the ocean compared to how many units are out there.
     
  14. Scarred Sun

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    Welp, this.
    What mentski said, and the inevitable stock of VMUs that have defective screens/internal boards but are otherwise fine.