Hardware Review: GDEmu - Sega Dreamcast SD Card ISO Loading Disc Drive Replacement

Hardware-Review-GDEmuAs of recent there's been a rather significant breakthrough in the retro gaming world. Similar to flash cartridges, console hackers have somehow found a way to trick disc based systems into running games from SD card. With the ability to now store and play a large library of game images from removable media, are the days of discs now nearing an end?

Introducing the GDEmu

Back in September 2012, it was announced that the brains behind the hugely popular Dreamcast emulator Makaron was working on a physical disc drive replacement for the Sega system. After sharing various photographs of console guts, development boards, and all sorts of wires, it was clear that Deunan Knute wasn't just toying around. His aim was simple: to bring the Sega Dreamcast a future proof solution should the likes of bit rot strike our beloved game discs.

After nearly a year and half’s silence, Knute finally returned to his LiveJournal page to document his progress. In February 2014’s blog post Knute not only revealed the rewards of his research, but also custom made prototype boards of the GDEmu project. Before signing off, he also hinted that a batch of boards may be made in the near future and put up for sale. After what we can only assume was a barrage of requests for a unit, a few weeks later Knute confirmed that his labour of love would see a short production run to gauge interest.

Needless to say, many months on the GDEmu continues to sell out as soon as it arrives on Knute’s newly launched website. Now coming on sleek black PCBs marked v5, this disc drive alternative has come a long way - but is it worth investing in?

Some Surgery Required

Before we head into the details, it’s worth noting that the way the GDEmu works is slightly different to that of a flash cartridge (similar to the Everdrive range). Instead of being something you can freely plug-in and remove when needed, the GDEmu is more of a permanent installation to the Dreamcast. Not only does it act as a disc drive replacement for loading games into memory, but it literally does replace the disc drive (something you’ll no longer be needing).

Although sounding daunting at first, the GDEmu is incredibly easy to install and requires nothing more than a single screwdriver. Simply open up the console, detach the GD-ROM drive, and plug the GDEmu into the now visible connector, reassemble. Done.

If for whatever reason the above tutorial isn’t visible, Knute has kindly detailed the process in a few easy steps. The most important of these worth noting though is that you need to make sure your console is the VA-1 model. This can be confirmed by looking at the underside of your console and seeking out a circled number 1 next to the system’s region.

Once installed in the console, the hardest part is over - everything from here on takes place on the PC and the Dreamcast’s control pad.

Getting started with the GDEmu

At this point in time you’ll need to choose your weapon of choice, an SD card to hold your many favourite Dreamcast titles. According to the official GDEmu website, SD cards over 32gb have not been tested with the device, nor should SDXC ones work with it. Feeling curious about this (and desperate for more space), we decided to dream and ordered a 128gb SDXC card to test with.

After reading other forum posts stating that these larger cards could indeed be used, as long as they were formatted correctly, we were feeling lucky. According to several GDEmu users elsewhere, the trick here was to use a standalone formatting tool that allows you to wipe SD cards larger than 32gb in the FAT32 standard. Without going too technical, all you’ll need to get the job done is a tool such as GUIFormat. Regardless of which size card you’ll be using, make sure it is formatted as above and ready for use.

With a clean card ready to go, you’ll need to make a few more preparations before you plug it into the GDEmu’s SD slot. Unfortunately, this disc drive replacement isn’t quite as simple as the drag-and-drop functionality we’ve grown to love with the Everdrive flash cartridges. As the GDEmu effectively tricks the console into thinking there is a disc in the drive, it needs to have a bank of images to cycle through in order to pull this off. With this in mind the GDEmu currently requires each game image to be placed into its own sequentially numbered folder, and then to be renamed as ‘disc’. So for example, this is how you’d layout a small selection of games on the SD card.

  • 01/disc.cdi
  • 02/disc.gdi (accompanied by its other tracks)
  • 03/disc.cdi

As this example shows, the GDEmu can read both GDI images and self-booting CDI images.

Upon turning the console on with these few images loaded onto the card, the first title will be booted into memory. Should you fancy moving onto game 02, a press of the button on the GDEmu while the console is on will instantly switch the disc in memory over. And obviously, another press would grab the third image before cycling back to the first if pressed again.

For those of you not feeling too adventurous, this is where the preparation ends - simply place the SD card back into the device and boot up your console.

For the rest of you thinking “where’s my game selection menu” or “how will I remember what game number 17 is later on?”, then keep reading…

Supercharging the GDEmu

Upon release, the preparation above was all that was needed for the GDEmu. Just a mere few months later though, retro gamers have decided that using the small disc change button over and over again to swap games wasn’t ideal. As a result, software known as GDMenu was created with the intention of sitting in position 01 on your SD card, all with the purpose of accessing every other image through an on-screen menu.

As shown above, the GDEmu automatically loads GDMenu (should it be placed in slot 01 on your SD card) when the Dreamcast is turned on. After a short loading screen, GDMenu then lists every single game installed on the card, based upon the name of each disc image. Using up and down on the control pad, you’re able to choose which game to boot into memory without ever needing to use the GDEmu’s hardware button.

Now this is all good, but if you’re anything like us, choosing which games to put on your SD card can often become a messy procedure. Starting with our favourites and then the various others we want to experience, the end result is anything but organised or alphabetical. As the video above will show, GDMenu is yet to become able to organise game images by name and instead lists them in the order they sit on your SD card. While you could indeed keep a long log of what’s in each of your numbered folder, remembering what each ‘disc.cdi’ file contains is no longer tricky - there’s an app for that!

This other crucial part to this Dreamcast swiss army knife is the custom built software, SD Card Maker for GDEmu. This simple bit of software for the PC reads your GDEmu SD card and then presents a list of your chosen games for re-arranging. After moving your games into a order more suited to your needs, hitting the save button will make the software go through your SD card’s contents, renaming all of the numbered folders until they match your new order.

Once done, simply plug your card back into the GDEmu and if all has gone to plan, GDMenu will now show all of your chosen games in the correct order.


This final point leads us onto one promising development. We carried out the process above on the 128gb SDXC card we purchased, and we’re pleased to say that 128gb SD cards do work on the GDEmu once formatted correctly. If you want to ensure you have the same success as us, we purchased ours from Amazon at this link.

Gaming on the GDEmu

With quite a lengthy set-up process and lots tinkering required, you must be wondering if the GDEmu is really worth it. After-all, Dreamcast games aren’t exactly expensive and discs work perfectly fine, right? Well retro gamers, be prepared to be amazed. Not only does the GDEmu act as a direct replacement to the GD-ROM drive, but it also loads games at a much faster rate than any laser can. Take Shenmue for example:

Despite loading the exact same game into play, the GDEmu’s lack of moving parts and physical media allows the device to just get on with the gaming. Long gone are the loud disc drive noises, and here to stay are improved load speeds. In the above example, the GDEmu takes just a mere 15 seconds to reach Shenmue’s title screen once powered on, while a standard Dreamcast console reading the game’s disc requires 26 seconds to do exactly the same. Although these are mere seconds were talking about, they make all the difference.

While we may be getting ahead of ourselves here discussing the speeds at which the device can read games, it’s worth taking a step back here to acknowledge what’s going on within. Not only does this device load a game into memory from SD card, but it does it with absolute ease. You’ll be hard-pressed to prove that there isn’t infact a game disc inside the console, something that can only be seen and heard through the quicker and quieter load speeds. Simply put, the device does exactly what it set out to do in the first place, and a little too well.

To give a bit more background on this fantastic compatibility and no fuss gaming, we need to revisit the short lived life of Dreamcast Serial Port SD Card readers. After a rather remarkable breakthrough was made in getting the Dreamcast to read data into memory from the Serial Port, various devices began popping up which allowed you to plug SD cards into the back of your console. As great as these were, running games on them (and well) was another matter. Not only was there huge compatibility issues present, but the actual speed of the device was lacking. The arrival of the GDEmu is a welcome one to many Dreamcast gamers, something which finally renders the loading of game ISOs via Serial Port SD card readers obsolete.

But before you toss aside your Serial Port adapter, the GDEmu can actually be used in conjunction with this dated device to give your Dreamcast some added oomph! For those unfamiliar with the adapter, some homebrew software known as Dreamshell was developed to grant the console its very own operating system equivalent. This allowed the aforementioned loading of games via SD cards through the adapter, amongst other things such as backing up original game discs in their rawest form. While these functions may no longer be needed, placing Dreamshell onto your GDEmu’s contents allows you to do various other little tweaks to your system, along with being able to back-up and restore save games on your Visual Memory Units. And before we leave this point, those still nostalgic about the VMU should look towards putting Dream Explorer onto the GDEmu too - a disc full of all the VMU mini-games and functionality to restore them.


Applications aside, our tests with countless game images continued. Not before long our SD card was packed with 61 different games, and of course GDMenu and the two other tools above. Out of these many games, we were hard pressed to make the GDEmu struggle. From Sonic Adventure to Power Stone, Shenmue to Sega Rally 2, everything worked as if there was really original discs being read in the system. This compatibility also continued with homebrew releases such as the fantastic Wind and Water: Puzzle Battles, to even unreleased titles like the incredible Propellor Arena. Emulators for other systems such as DreamSNES (a Super Nintendo emulator) also worked on the device, expanding the system’s potential library to thousands upon thousands of other retro titles. Every now and then there would occasionally be the odd game which showed up as ‘Unknown Disc’ on GDMenu, but after trying a different ISO of the same game, this issue was soon remedied. In the end, the only game we seemed unable to run was Unreal Tournament which was stuck in a boot loop.

One of the final things to note regarding this compatibility is that the GDEmu makes the Dreamcast region free. This means that no matter what region system you have installed the device to, it will boot games from all around the world with no fuss whatsoever. In order to get the most out of this, our GDEmu was placed into an NTSC-U system so that everything ran at 60hz by default - but it did mean we needed to carry out the R422 modification to get PAL 50hz games displaying correctly.

As fantastic as all of this is, there are a few things worth mentioning regarding the GDEmu that should be noted before making a purchase. While we were rather excited to get a 128gb SD card working on the device, the GDEmu has a readable limit of 64 folders. This means that those hoping to store the entire library of classics on one SD card will instead need to look at having several cards spreading out the games on each. Knute has stated that this limitation is not going to be resolved, as it requires more expensive hardware to remedy. Alongside that, the only other issue with the GDEmu is that it appears to be a victim of its own success. Although it does boast a fantastic compatibility, we found that Space Channel 5’s background FMV sequences loaded almost too quick for the system, occasionally leaving Ulala walking a split second ahead of the action. Having said that, these are tiny niggles compared to the positives the installation of a GDEmu can bring.


If you haven’t already guessed by now, we have been absolutely blown away by this incredible device. To even think that technology has arrived to mimic disc drives and out-perform them is simply mind-blowing.

The GDEmu is an absolute must have for retro gamers and those affixated with Sega’s last ever system. While the initial set-up may be a little fiddly, it’s worth pushing through for the ability to have 64 strong library of 128-bit classics sat within your console without a disc in sight. Given its compatibility is near perfect (at least from our testing), it’s highly unlikely you’ll be reinstalling your GD-ROM drive anytime soon.

Available from Knute directly at €100 + shipping, those interested in the GDEmu should keep a close eye on the ordering page as units appear to sell out as soon as they arrive.

Link: GDEmu Official Website

Last Updated ( 16 November 2014 )  


Better known as Adam offline, Cauterize is one of RetroCollect's final bosses with an unhealthy addiction to pixels. When he's not out searching the web for the latest retro gaming news or creating content for RetroCollect, he'll will most likely be found working on his Sensible Soccer skills.

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(Link to this comment) Tomleecee 2014-11-16 17:33
Nice review! Looks like I need to get involved in some GD Emu action now. My wallet is going to cry.
(Link to this comment) BuckoA51 2014-11-16 19:12
I do think this http://renovation-3do.narod.ru/USB-GDROM_Controller.htm looks like a better product, but importing it from Russia is a lot harder.
(Link to this comment) Speedle 2014-11-17 11:24
I managed to get one of these from the initial production run and I can honestly say it is EPIC! Loading times are super fast, I've not come across any issues when using it to play my games and the addition of the GDmenu thanks to the legends at Assembler really does make using this a breeze :)

Highly recommended!
(Link to this comment) DarakuTenshi 2014-12-09 13:56
Stuff like this is what is getting me out of collecting video games. I'm so glad! I have realized that I am much more of a gamer than a collector after things like Everdrives have been coming out. The only games I really collect anymore are TurboGrafx/PCE and Neo-Geo.
(Link to this comment) manic23 2015-03-21 14:39
I need to correct you one one VERY important point, you state that the GDEMU makes your Dreamcast region free, this is NOT true! maybe it works if you are laying PAL games on an NTSC Dreamcast but not the other way round. Even the creator of this device confirms it on his site, https://gdemu.wordpress.com/2014/09/12/joyride/ (scroll down to near the end). You need to convert NTSC games first using GDROM Explorer application to region free before they will work with this device.

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