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Einhander
rank 20
Posted:
Sun Aug 16, 2015 5:54 am
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Recently I managed to pick up a GDEMU, which is an ODE (optical drive emulator) for the Sega Dreamcast. They are built by hand by a person in Poland who sells them direct to customers as opposed to through an online storefront:



The GDEMU completely replaces the GDROM drive inside of the Dreamcast with a small PCB that includes an SD card reader. Disc images of Dreamcast games are added to the SD card, the SD card is inserted in the GDEMU, and the games can be played directly from the card. Each disc image is placed into a folder on the SD card, and there is a small button on the GDEMU itself that switches between folders (sort of like switching between "pages" on a 4X VMU). You can throw a "menu" disc into the first folder and boot directly into a menu with a list of games, from there you can either select a game to start or you can press a button to go to the Dreamcast's normal menu (for checking VMUs and changing systems settings/etc).


(These pictures aren't mine, I just grabbed them off of the internet)

One of the biggest upsides to the GDEMU is the fact that reading data from an SD card is much, much faster than reading data from a GDROM drive (even on a paltry Class 4 SD card like the one I am using), and as a result the loadtimes for games are significantly reduced. Since there is now no GDROM drive, you don't hear any grinding noises coming from the lens motor either, now all you hear from the Dreamcast is the quiet hum of the fan and the occasional beep from your VMUs.

There are a number of other methods available for bypassing the GDROM drive on a Dreamcast, outside of the GDEMU we also have a USB based replacement called the USB GD-ROM, and although technically it's not an ODE we also have the serial port SD card adapters that are used with Dreamshell. While the USB GD-ROM has a benefit of using more common (and cheap) USB devices (anything from USB sticks to hard drives up to the ridiculously huge firmware limit of 2TB), feature wise it's pretty much the same as the GDEMU (100% compatibility, reduced loadtimes, no more wear and tear on your laser, no more handling discs, etc). While the GDEMU only "officially" supports SD cards up to 32GB, 128GB SD cards have been tested and work fine. A major downside to the USB GD-ROM is that it requires complete disassembly of your GD-ROM drive if you want to run it with the metal shield on top, and while it allows you to have either an internal or external USB port, an external port requires you to cut a chunk of plastic out of your DC's shell.

Dreamshell partnered with a serial port SD card adapter is a decent solution in a pinch, or if you don't want to spend a ton of money on an ODE (GDEMU is around $120 after currency exchange, USB GD-ROM is over $150), but its compatibility is abysmal and so far the developers haven't been able to get enough speed out of the serial port to make it a reliable option. The major upside to the serial port adapters is that they are cheap ($10), and are plug and play - no system disassembly required.

The major impetus for me to get a GDEMU was that my current DC's laser was failing. Cleaning and POT adjustments can only get so far, and I knew that eventually it would become unusable. While DC's are pretty easy to get ahold of in the US (and not that expensive), I really wanted a solution I could get and then not have to worry about again, so a solid state board like the GDEMU was perfect (not to mention convenient, the unit arrived just two days after my laser stopped reading games for good). I'm still thinking of picking up a cheap $10 serial port adapter though, solely for backing up my VMU saves.

Do any of you guys have a GDEMU or USB GD-ROM? Since getting the GDEMU I have sunk a lot of time playing different DC games to see how awesome it is to see such short load times (I was going to make this post days ago and I was going to record some gameplay footage but I've gotten hooked on PSO again so whenever I fire the DC up lately most of the time I end up just playing that). I'd honestly say that something like the GDEMU is the best possible accessory to get for the Dreamcast. If you're seeing issues with your DC's laser or are just looking for a way to reduce loadtimes and keep your discs in their cases I'd definitely recommend checking one of them out.
 
lordnikon
rank 86
Posted:
Sun Aug 16, 2015 3:12 pm
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This tech is just awesome. Do you know if you can load content that exeeds the Dreamcast's GDROM size limit? For instance having a 2GB disc on the SDCard? The reason I ask is, things could get very cool for Quake 3 and custom maps Wink

Also can it be written do and read from by moving files to and from the VMU?

The Tokyo Extreme Racer games are perfect to run off the GDEMU because all they do is seek non-stop loading City data as you are driving.

I have a Dreamcast where the laser is dying, so this would be perfect for that unit.
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Einhander
rank 20
Posted:
Sun Aug 16, 2015 6:09 pm
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I'm not positive that it could exceed the GD-ROM's storage limit, but since it's literally just running disc images I don't see why not. Custom Q3 maps would be pretty amazing. It would be possible to alter all sorts of things in DC games, from music to textures and etc without having to worry about the 700mb or 870mb limit (on 99 minute discs) that would be imposed if you were burning your customized game to a CDR. I know a lot of people that alter music for DC games have to worry about filesizes and have to lower the bitrate of the music to compensate for it, so something like this would make that much less of an issue. With Quake 3 converting PC maps to whatever format they are in on the Dreamcast should be possible, the only thing to remember when building custom maps is that they have to be small enough to run well on a system that only has 16MB of RAM. Theoretically cracking open pak files would mean it would be possible to alter sounds, textures, and even models, but I have no idea what kind of work that would entail.

SD cards can't be written to currently because it's just emulating the disc drive. It pretty much turns the DC into a cartridge based system and your SD card into a multi-cart. Moving files to and from the VMU would be easier to do by grabbing a serial port adapter and using Dreamshell. I suppose if someone wrote a menu that could do it it would be possible, but I don't know if the DC would even support sending write commands to the disc drive.

Also, funny you should mention Tokyo Xtreme Racer - TXR2 was one of the first games I tried after installing it, I wanted to see how fast the cars load when you are moving between them in the car selection menu. It was so much smoother than running off of a disc, it was awesome. If my actual laser wasn't toast I could do some comparison videos and upload them. Everyone who does comparison videos seems to use Shenmue, which is a fantastic game, but not a very good representation of how loading is done on most Dreamcast games. Load heavy games like TXR, Half Life, or even non-games like Dream Explorer are better examples of the benefits gained from an SD card.
 
lordnikon
rank 86
Posted:
Sun Aug 16, 2015 8:36 pm
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Interestingly enough, I think the worst developed games are needed to see how much the GDEMU can help slow loading times. The really good games are already going to have pretty fast loading.

Maybe Soldier of Fortune's load times will finally be mitigated by the GDEMU:

https://youtu.be/S1HdQ5tYO50?t=189
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Kbuzz
rank 23
Posted:
Thu Aug 27, 2015 9:44 pm
quote : #5
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I'd love to get one of these. Last I checked, the compatibility was decent but not 100%. I guess it's improved since?

I'd like to see how Garou Mark of the Wolves runs. I remember the Dreamcast version needing to search the disc for every little sound effect to the point where some would just be skipped altogether.

Would also be a great way to enjoy some modded and patched versions of games without having to cut anything out to fit on a cd-r, or playing imports without a boot disc / modchip.

Cutting out loadtimes, laser maintenance, and motor sounds all in one go is pretty huge in prolonging the life of the hardware.
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petterk
rank 9
Posted:
Fri Aug 28, 2015 10:59 am
quote : #6
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I have one of these aswell, and have not found a single game that did not work.

I use raw GDI dumps of it (disc.gdi) and they load just fine. Nothing cut out or anything.
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Einhander
rank 20
Posted:
Sat Aug 29, 2015 6:22 am
quote : #7
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Kbuzz might be thinking about the SD card adapters that plug in via the serial port. Compatibility for those is nowhere near 100% and for technical reasons it never will be.

The upside to those devices is that they only cost $10-$20 online, vs $120 though.
 
Kbuzz
rank 23
Posted:
Mon Aug 31, 2015 5:00 am
quote : #8
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Nah I own an SD adapter. Mostly use it to backup vmu saves. Early firmware versions of gdemu had some compatibility issues. Great to see they've ironed those out.

I'll be happy to never burn a cdi ever again!
  _________________
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