2019 been such a great year for Sega Genesis
and Mega Drive fans, hasn’t it?
Sure, we’ve seen tons of great options over
the years for enjoying the system’s most
popular games, but I’d say that 2019 is
the year that everyone – including Sega themselves
– went all out.
Thanks to consoles like the Mega Sg from Analogue
and the Genesis Mini, wireless and wired controllers
from 8bitdo and Retrobit, and fantastic projects
from the community like the Triple Bypass
mod, it’s easy to see why Sega appreciation…
AND game prices are on the rise.
The cherry on top comes from Spain based developer
TerraOnion, who spent the last couple of years
developing what could be considered the ultimate
Sega flash cart – The Mega SD.
This device not only supports the requisite
Genesis and Master System games, but at long
last delivers something that myself and others
have been clamoring for – Sega CD-ROM games.
We’ve been able to take a look at the Mega
SD thanks to a review unit sent to us by TerraOnion,
so let’s dive in and see what this thing
[ MUSIC: “Principle” by Matt McCheskey
The early 90s were an interesting time for
the video game industry.
Cartridges had long been the preferred media
for consoles, and for good reason.
Not only are they fast and efficient…but
more importantly, they’re extremely durable.
But as games grew in size and complexity by
leaps and bounds, and it was clear that developers
needed more leg room.
When NEC released the CD-ROM addon for the
PC-Engine in 1988, it was off the races to
see who would be next to utilize what seemed
at the time a limitless canvas of data storage
at an exponentially lower manufacturing cost.
Sega delivered their CD-ROM expansion in Japan
in 1991 and throughout other regions over
the course of the next two years.
In Japan and Europe, this device was known
as the Mega CD, while North America came to
know it as the Sega CD.
Connecting to an edge connector hidden inside
an expansion slot on Genesis, the Sega CD
more than doubles the console’s height.
CDs are loaded into the system through a front-loading
tray, which really drove home its premium
feel…and let’s face it, it just looks awesome.
The added girth wasn’t just for show, either.
Inside was a hodgepodge of additional tech
for developers to play with, including hardware-based
scaling and rotation, which was a staple of
the Genesis’s closest competitor, the Super
This added hardware didn’t come cheap, landing
at nearly 300 dollars in the US, although
a number of pack-ins were included to help
sweeten the pot.
Granted, early games didn’t seem to offer
much that couldn’t already be done on a
cartridge, the system’s library ended up
being fairly decent for those determined enough
to wade past a glut of Full Motion Video games
– which hey, a lot of those are pretty fun
A number of hardware revisions, from lower
cost resdesigns to streamlined, all-in-one
consoles, followed over the Sega CD’s lifespan.
While the add-on sold fairly decently worldwide
for the time, it’s often grouped in with the
32X as a high profile failure which tarnished
Sega’s reputation in the West.
Whether it’s due to aging hardware or the
deterioration of CDs themselves, the Sega
CD is yet another example of the fragility
of disc based consoles.
As such, a number of capable members of the
retro gaming community have sought to merge
the aging tech with modern hardware.
Optical Drive Emulators – also known as O.D.E.s
– do away with the tiny moving parts of a
disc drive and whisking the game data away
from scratch-prone discs to the relative safety
of solid state media.
We’ve previously talked at length about
various ODEs for the Sega Saturn and PlayStation
1, but perhaps the most elaborate ODE came
in the form of TerraOnion’s Super SD System
3 for the PC-Engine and Turbografx-16.
The SSDS3 connects to the back of the console,
allowing the user to not only play Super CD-ROM
games without the need for original hardware
or expansion cards, but also HuCard ROMs as
well – all to say nothing of how it’s also
a plug-and-play RGB video output solution.
While the SSDS3 did struggle with various
challenges at its inception – mostly surrounding
its video output capabilities – it’s in a
pretty great spot now.
Thanks to input from the community, talented
modders, and electrical engineers, a number
of firmware and hardware fixes have helped
to optimize the device.
Naturally, the big question was: what would
TerraOnion do as a follow up?
Most, including myself, were hoping for a
Sega CD focused device.
The biggest hurdle that has prevented such
a device from becoming reality is that the
Sega CD is so much more complex than the PC
Engine CD system – which isn’t much more
than just a CD drive.
The Sega CD is a system unto itself with many
discrete chips that enhance the power of the
Well, in the summer of 2019, TerraOnion announced
that they had overcome these challenges by
unveiling the Mega SD, an ODE for the Sega
CD… and so much more.
It’s available for about 260 US dollars via
I think the most surprising thing about the
Mega SD is the way it immediately defied expectations.
I always imagined that a Sega CD replacement
would attach to the edge connector the same
way that a real Sega CD system would.
When the MSD was revealed as an oversized
cartridge, I was pleasantly surprised that
this much more appealing form factor was even
Housed in the same type of smokey, translucent
plastic that the SSDS3 came in, the size and
shape is virtually indistinguishable from
a Virtua Racing cartridge.
On the side, you have a micro SD card slot
and a singular physical button.
Inside is a blue PCB populated with a number
of chips, a Green access LED and a Spartan
The cartridge edge is very subtly chamfered
to prevent wear and tear on the system’s
slot while drawing the correct voltage.
In fact the whole device draws LESS power
than a real Virtua Racing cart!
Which really leads me to think: to classify
the MSD or heck, even the SSDS3 as an “ODE”
is a bit inaccurate.
A typical ODE replaces the drive functionality
alone, while the rest of the hardware remains
This is total hardware emulation via the FPGA,
so think of it like this – the Mega SD is
as much a Sega CD as the Super Nt is a Super
NES or the Mega Sg is a Sega Genesis.
Supporting FAT 32 or ExFAT formatted Micro
SD cards up to 400 gigs, you should have more
than enough space for anything you want to
play from region to region.
The Mega SD will work on most hardware variants.
The original Model 1 and Model 2 Genesis will
be the go-tos for most who choose original
The Genesis 3 and the portable Nomad will
also work, but both will take different mods
to get the fully desired functionality, such
as CD audio.
But it’s kinda crazy seeing Sega CD games
running on a Nomad screen, isn’t it?
What about system on a chip style clone consoles?
Well, I just had the Gamerz Tek MiniGen on
hand to test… and color me surprised – it
works… to an extent!
Not sure if a mod would fix that, or if anyone
even cares to try to figure it out.
But it’s the one-two punch combo of the Analogue
Mega Sg and Mega SD that may just provide
the ultimate road to 16-bit heaven.
Just remember to tick the “enable cartridge
and CD audio” box while unchecking “automatically
enable CD audio” in the Sg’s options if
you want it to get the most out of it.
As usual, I’ll be showing a bunch of material
captured from different consoles and revisions
through the entire episode.
Keep in mind that as the device gets into
more people’s hands – I’m sure lots of
quirks will pop up.
Thankfully, up til now, TerraOnion has been
pretty good at stamping out glitches or incompatibilities
at the firmware level.
Speaking of firmware, the MSD does keep these
updates locked behind a user account on the
TerraOnion website, which requires you to
register your device’s serial number.
This number can be found on the back of the
cartridge itself or via the option menu in
the front end user interface.
The firmware generated seems to be tailored
to only install on a unit with a matching
The main menu is pretty self explanatory.
You scroll up and down to navigate the various
directories you’ve previously set up on
the SD card via your computer.
If you’re using a Mega Sg, set the reset
mode to HARD in the SD’s options, which
ensures higher compatibility with games working
by causing a hard console reset when you choose
a game to play.
In general, it’s probably best to just leave
it set this way.
Whether it’s pulling game ROMs from your own
carts using a device like the Retrode, or
ripping disc images from your CD games using
a computer program like ImgBurn[a], you’ll
have to put in a lot of legwork to get everything
just the way you like it.
If you decide to skew towards grabbing the
games from elsewhere… well, that’s up to
you to figure out.
While Sega CD support is probably the main
reason people would be interested in the MSD
in the first place, it’s easy to forget that
you can play all kinds of other games, too.
Yeah, it might be hard to get excited about
Genesis and Mega Drive game support in a world
where Krikzz’s Mega EverDrive has been a
thing for years, but the all-in-one functionality
is a big part of the appeal here.
Predictably, Genesis games seem to run exactly
as you would expect.
Once you start a game, you can bring up an
in game menu by pressing Up + Start on the
controller, which has several functions specific
to running regular Genesis games.
While cheat codes and saves states are standard
fare for higher tier flash carts, fans of
the latter will be pleasantly surprised by
a whopping 8 – yes, 8 – individual save state
slots per game.
I know this seems extreme, but I love the
idea of keeping a set of save states that
would allow me to quickly jump back to later
Save state files are stored on the SD card
within the STATE folder and have matching
file names to the ROM, so they can be easily
Generating or Loading a save state can cause
some odd behavior with the Genesis sound hardware,
like weird sounds or just music not playing
Thankfully, it tends to correct itself when
something happens that would cause the music
to start over – like dying or pausing and
Of special note is special support for Virtua
The original cartridge uses a specially integrated
chip, making the Mega SD, to my knowledge,
the very first Genesis flash cartridge to
be capable of playing it.
Some unlicensed games with enormous ROM sizes
also work – such as Pier Solar.
However, make note the in-game menu cannot
be accessed while playing some of these special-case
Master System cartridge and card games are
both supported via the Genesis’s Master
Well, except F-15 Fighting Falcon, which originally
used a specific graphical mode not carried
over to the Genesis hardware.
SMS games use the button located on the side
of the Mega SD to pause the game, similar
to a real system.
Unfortunately with Master System mode, there
is no in-game menu and consequently, save
states are not possible.
As far as I know, the only flash cart that
supports save states for SMS games is Krikzz’s
Master EverDrive X7.
This mode does offer optional emulation of
the Master System’s Yamaha YM2413 FM expansion
audio, which can be toggled on and off in
the main option menu.
Finally, 32X ROMs are supported IF you have
a 32X unit attached to your console.
I understand this might be a bummer for some,
but it simply comes down to the way the Genesis
and 32X interact with each other.
We just gotta accept that it’s not viable
right now, and that having it would require
at the very least a bigger and more expensive
Having a 32X attached does come with a slew
of considerations, though.
In short, you lose the ability for any sort
of in-game menu, even for regular Genesis
games, which means no save states.
You also won’t be able to boot Master System
OR Sega CD games.
In a nice effort to quell confusion, incompatible
games won’t even show up in the menu at
all when you have the 32X attached.
All variants of save file types are supported
– from the SRAM used by most games to the
EEPROM types used in certain games like Wonder
Boy in Monster World.
With the most recent Firmware update, save
files are simply drag and drop from EverDrives
or real cartridge via a Retrode.
Gently place the .SRM files into the BUP folder,
and match the file name to the game ROM.
By the way, if this is a subject you’d like
to learn more about, check out our episode
on cartridge save preservation!
Of course this is all good stuff, but it’s
the much touted Sega CD support that most
of you are here for, right?
If you’re a fan of the system like I am,
then the ability to play these games off of
solid state media makes tips the scales and
makes the Mega SD an essential and unique
CD-ROM game images need to be ripped as .bin,
.img or .iso and are required to have a .cue
Sorting each combo of disc image and cue file
into their own folder gives us what we see
as a standalone game in the Mega SD’s menu
Multi-disc games need to have all files in
the same folder and labeled in a way that
they appear in correct disc order.
Disc 1, Disc 2… you know what I mean.
CD games do have the particular caveat of
requiring a BIOS file, which can be a bit
of a prickly subject because they are still
However you decide to obtain these files is
completely up to you.
You’ll need to load them into the options
of the main menu – one for each supported
One important thing to keep in mind is that
Sega CD functionality on the Mega SD will
not work at all if you have a real Sega CD
connected to your console because it causes
some sort of bus conflict.
And so, his mean no Sega CD game loading on
the all-in-one systems such as the CDX or
As you may have already guessed, this also
means that the handful of 32X CD games aren’t
Games are auto detected by region via the
header of the disc image, and will boot up
the correct BIOS file.
Once you boot a game, everything functions
just like a regular Sega CD.
You can play the redbook audio from here as
if you had a disc inserted or manage your
Backup RAM and save files.
Once you actually start the game, you’ll
be greeted with that all too familiar jingle.
Most CD-ROM consoles up through the PlayStation
used dedicated built in memory to store save
games, with the option to expand this space
with RAM carts or some other device.
So, how does the Mega SD deal with this hurdle?
Matching what a real system would do, the
Mega SD has the option to generate a single
pool of internal memory and accompanying RAM
cart which will be automatically loaded when
you play a CD game.
This file is stored on the SD card and consists
of an equal amount of internal space as a
real Sega CD, while the RAM cart storage is
a bit smaller than what you’d get using
an official RAM cart.
If you want to function within these confines,
and juggle files back and forth, you can do
But really, who wants to jump through those
hoops when you can have unlimited space.
Enabling the “per game” backup RAM option
creates an internal and RAM cart pool PER
That one game will have an entire, luxurious
…meaning you’ll never run out of space.
Like cart games, CD backup ram files have
a .SRM extension and are stored within the
BUP folder for maximum convenience and easy
The in-game menu does work with with Sega
CD games, which is pretty convenient.
Although there are understandably no save
states, you can reboot the game or jump back
to the Mega SD menu from here.
This is also how disc changes are normally
handled with multi-disc games.
When you reach a disc swap point, go into
the menu and change it.
Alternatively, if you long for the time honored
tradition of getting off the couch and swapping
the disc, pressing the button the Mega SD
will achieve the same results.
For fun, I tried swapping discs during the
opening FMV of Night Trap, causing it to play
random scenes from disc 2 and generally just
I thought it was cool that the game behaved
the same way if you did something similar
on a Sega CD model 2 – a testament to how
accurate the Sega CD hardware emulation is
on the Mega SD.
Thankfully, we don’t have to think twice
about video quality output with the Mega SD,
but we do have to consider an important part
of the CD gaming experience: Audio.
TerraOnion has enlisted the help of FirebrandX,
who has developed a number of audio centric
mods for the Genesis, to design an amp circuit
to drive analog audio into the Genesis circuitry.
As a result, there’s quite a few options that
address the sound in particular.
You can set the default CDDA and PCM audio
levels back in the main options menu.
CDDA stands for Compact Disc Digital Audio,
referring to the audio on disc.
PCM audio comes from the additional sound
chip in the hardware itself and is used for
both sound effects and some music tracks.
These audio levels can be tweaked separately,
but the default 80% value mimics the levels
of real hardware.
Going beyond that amount might cause audio
distortion in some games.
These levels can also be temporarily altered
via the in game menu – which is pretty handy
for games where the audio balance just doesn’t
In addition, the CDDA Treble Boost and PCM
Lowpass filter options available in the main
menu can be ticked to bring the overall sound
closer to original hardware combination.
While you might not think that it would be
tricky to emulate the characteristics of CD
audio, it did take the team some work to match
the sound signature.
The most recent firmware combines FBX’s
attention to detail with the help of MDFourier
to get the audio as close to as close as possible
to the original hardware.
In this case, a VA3 Model 1 Genesis and a
Model 1 Sega CD.
MDFourier is an ongoing open source project
dedicated to analyzing original Genesis and
Mega Drive audio for preservation and to assist
in producing accurate emulation.
Finally, we were told that there may be a
slight buzzing while the SD Card is being
accessed, and may be heard during moments
of complete silence.
TerraOnion even delayed the announcement of
the Mega SD for several months while they
worked with Electrical Engineers to reduce
this as much as possible.
I’d say it was well worth the effort because
I have crank the volume by at 40 decibels
to bring it out in my captures.
But, y’know, if you can pick it out then
consider me extremely impressed.
When CD-ROM games were first arriving on the
market, one mark you’d always see levied
against the medium is load times.
For the most part, I’d say that Sega CD
games aren’t too horrible in this area overall…or
maybe I’m just used to it by now.
But one major benefit that anyone would expect
out of the Mega SD is the ability to speed
up load times.
And speed them up, it does.
In some cases though, audio and video are
timed by the developer in such a way to keep
everything in sync.
Speeding up load times might cause them to
fall out of sync.
[ Game Audio ]
In which case the Emulate Seek Time option
comes in handy.
This will slow everything down to mimic the
read speed of the original hardware.
The firmware actually keeps track of the games
that need this applied, so you can leave the
toggle off at all times – the system will
slow it down when it’s needed.
[ Game Audio ]
For the most part, I’d say that the improvements
are fairly minor – a second or two here and
But in some games, such as Willy Beamish….
[Game Audio ]
Which has excruciately long load times to
do anything… well, it’s significantly
[Game Audio ]
Doesn’t make the game all that more playable,
but I guess fans will be happy.
[Game Audio ]
One of the more interesting experimental features
is the Scaling Speed Up option, which speeds
up the Sega CD’s VDP for smoother scaling…
in certain instances.
Although it’s recommended to leave this off
most of the time, it might be fun to see how
it affects certain games.
Now that you know what this thing is capable
of doing, let’s relax and have some fun.
What are some things you should check out
if pick up a Mega SD?
The Sega CD may not have a vast library, but
it does have some notable games that I feel
are absolutely essential.
Not only that, but we can’t forget what
might just be the ultimate use of the Mega
SD – MEGA DRIVE PLUS games.
Did you know that a game could be programmed
in such a way to use both the Genesis and
Sega CD hardware in tandem?
The game itself plays off a cartridge while
the Sega CD could be used for music tracks.
It’s a mystery why Sega never took advantage
of this ability… much less publicized it.
How cool would this have been back in the
As far as I know, Watermelon’s Pier Solar
and the Great Architects was the first game
to utilize this hidden capability.
Terraonion knew this sort of functionality
would be heavily desired.
Super NES fans have been enjoying CD audio
“hacks” of cartridge games using the SD2SNES
flash cart and it’s MSU1 chip for some time
Well, Terraonion delivers the goods with what
they call Mega Drive Plus games.
It’s about time Sega fans can get in on the
action… but the downside is that there’s
just not a lot of them yet.
The first one I played was OutRun, which mixes
in the arcade music for the Genesis game.
I guess it’s alright, but I don’t love this
version of the game and the audio playback
is fairly quiet.
There’s certainly ample room for improvement
here, but the other Mega Drive Plus release
thus far is virtually perfect – and it’s for
one of the first games I’m sure came to
mind when you first heard of this feature.
Streets of Rage 2.
Whew, this is awesome.
The music is balanced perfectly and the chosen
music tracks sound like something that would
have existed if Sega themselves had done this
– and they should have.
I gotta tell ya – there’s so many Mega Drive
Plus games I’d like to see in the future.
I’m just spitballin’ here, but could you
imagine a Michael Jackson’s Moonwalker with
the real MJ tunes?
I’m excited about this stuff.
The Sega CD was my first exposure to the divisive
Working Designs, who were responsible for
localizing some choice RPGs in a time when
they weren’t all that popular in the West.
Other than their sometimes dated translations,
one of the big things that makes Working Designs
so contentious is their knack for altering
aspects below the surface.
Increasing difficulty… have restrictions
on saving your games… and more.
If these sorts of things rub you the wrong
way, I recommend checking out the UnWorked
Designs hacks, which undoes a lot of tinkering
while keeping the original translation.
One the disc image has been patched, these
are absolutely playable on the Mega SD.
I went into a bit more depth on these in our
Useful ROM hacks episode, so if you want some
specifics of what was altered – check that
Back in 2015, a programmer named Brian VanBuren
did a lot of legwork when it comes to decoding
Sega CD save RAM files.
He compiled the various utilities he developed
in an archive called SCDTools.
An offshoot of this project was BACKUP SHELL,
an interface that can be run on a real Sega
CD and allows you to copy preselected save
files to the internal or cartridge memory.
The ISOs included with the Backup Shell download
will boot using the Mega SD.
You can also tamper with the hex data of the
save files to help give you more money and
Once you copy the saves, just rename associated
the BACKUP Shell .srm file in the BUP folder
to match whatever game you want to use those
Although it seems like much of this work was
unfortunately under appreciated, Brian VanBuren,
if you somehow see this, thanks for making
So what about general games worth checking
Everyone knows about the expensive ones – y’know
Keio Flying Squadron…
Shining Force CD
and of course Snatcher….
But do yourself a favor and beeline for Road
Avenger, which is perhaps the greatest FMV
game ever made and is such an over the top
rollercoaster that it tends to leave a strong
impression on everyone who played it.
It also has the best opening theme of all
time… well at least in my opinion.
And if you like that, check out Gaming Muso’s
cover of it here on youtube.
He totally does it justice.
Star Strike is a FMV rail shooter that was
originally cancelled, and then later released
by Good Deal Games in 2001.
And it….. IS….
This is exactly the kind of stuff I play FMV
It’s so stupid…
I love it.
As a lifelong Sega fan, how cool is it to
finally see this lavish attention put on the
I, for one could have never imagined when
I was 13 that I’d be playing a CD game off
of a cartridge.
So what do you think?
While I feel the Mega SD easily takes the
crown of essential flash cart for the Sega
Genesis, others might feel that it’s price
is a bit too hefty versus the alternatives.
A real Sega CD can play burned discs without
modding the system, which might be plenty
for some, but that does require you to have
the hardware already.
Or heck, maybe you don’t even care about
the system at all, in which case…
I get it.
But, the potential for future Mega Drive Plus
games brings everything home, at long last,
giving the Genesis an SD2SNES equivalent that
has been long overdue.
We may never see a year full of loving innovation
directed toward the Genesis ever again.
But that’s OK, I can’t think of anything
else that I’d want.
[a]Should we research and vet an alternative
Sometimes people comment with warning about
it having adware or something, or at least
certain installations do.