||Hack the Dreamcast Visual Memory Unit
Play homebrew games on
Dreamcast's LCD-toting memory card
One of the more unique aspects of the Sega Dreamcast is the visual memory
unit, a 128-KB memory card with a 48 32 resolution LCD monochrome
screen. The VMU has clever uses for memory card management (you can
manipulate and delete saves without plugging it into a Dreamcast and
even connect two memory cards to trade saves), but
we're really interested in it for its ability to
store games. It comes with a battery and built-in controls (a D-pad
minicontroller and two buttons), so you can play standalone games
using it, even though it normally plugs into your Dreamcast
Basically, the device resembles a teeny tiny Nintendo Game Boy. As
such, it's eminently hackable.
The VMU, also known as the
Visual Memory System (VMS)
in the United States, never reached its full potential during the
height of the Dreamcast's popularity. If connected
to your Dreamcast controller, it would sometimes show the game, logo,
vital statistics, or other information while playing games. Some
multiplayer games provided personal data, hidden from your opponents.
You can also use standalone VMU
games with a few commercial titles. Games such as Power Stone use
standalone VMU games intriguingly. Sega's Sonic
Adventure is particularly interesting because it allows you to grow a
cute-looking Chao creature on your VMU and then import this data into
the Dreamcast game. There were also several official VMU games
downloadable from the Internet via the Dreamcast's
web browser, for titles such as Namco's excellent
fighting game Soul Calibur. However, with the
Dreamcast's cancellation and the homebrew
scene's interest, the VMU has seen significant and
interesting independent development efforts.
Acquiring Your VMU
As discussed previously, you should be able to find a Dreamcast
for anywhere between $5 and $10 at your local specialty game store or
on eBay. They come in a variety of fetching colors, with even
limited-edition VMUs sporting Godzilla and Sonic Team themes. White
and transparent are the most common colors, so don't
spend too much time collecting. Just pick one up.
When you track down a VMU, whether bought in the store or unearthed
in the closet, you may find that its batteries have died. The unit
takes two CR2032 lithium batteries, also found in watches and
cameras, so it's easy to track down replacements for
around $5 for the pair. Just remove the small screw holding on the
back compartment and replace the batteries to return your VMU to
Arming Your VMU
Transferring files from your PC to your
Dreamcast may not be exactly
straightforward. You have several possible choices:
- Hop online
The advantage of this method is that you don't need
to burn CDs to manipulate VMU games. A major disadvantage is that
you'll need to take your Dreamcast online somehow,
which probably means you need a dial-up ISP or an ultra-expensive
Dreamcast broadband adaptor.
- XDP for fun and VMU profit
A simple if dubious method for acquiring VMU saves is to burn a disc
of the XDP Standalone utilities and web browser package from the
Psilocybin Dreams site (http://www.psilocybindreams.com).
Click one of the browser options to reach the main menu, then use the
digital controller to choose the Menu option. Finally, choose the VMU
Mini Games option to see a web page (as if you were actually online)
that includes over 30 freeware, freely distributable VMU games. This
includes the vast majority of the games we'll talk
about in the next section. However, the disc also contains highly
customized versions of Dreamcast browser software that, while
possibly being abandonware in some abstract sense, the developers may
not have permission to distribute. Bear this in mind before
This solution works because the developers burned an offline web page
and a web browser onto the same disc, so it's a
little like you're online.
- VMU copy
While this option is excellent if you have normal Dreamcast save
games that you'd like to transfer to your Dreamcast
without going online and grabbing them, there's
currently no functionality to detect if a save is actually a VMU
game, so VMU game support is broken. Perhaps this will change in the
VMU Development Resources
Do you think you're a hardcore programmer capable of
creating your own VMU games from scratch? It's
definitely possible, but it won't be easy. Start
with the VMU Development page at http://www.maushammer.com/vmu.html.
This site provides info on a VMU assembler, available in Windows,
Linux, and even Amiga (!) flavors. However, VMU development has poor
documentation and requires assembly code, so it's
hardly straightforward. Also bear in mind that some of the interest
in the Dreamcast VMU scene started to die out when the DC began to
fade, so many of these pages have fallen into disarray in recent
To aid you in your programming task, and heck, even to run the
previously mentioned VMU games on your PC as a test, download a PC
emulator that claims to emulate the VMU. This should be handy if you
want to check ongoing development. However, both the Windows-based
VMU emulators, DirectVMS (http://www.dcemulation.com/emu-directvms.htm)
and SoftVMS (http://www.dcemulation.com/emu-softvms.htm),
seem to crash with some regularity on the most recent versions of
Windows. You may have better luck with a Mac OS port of SoftVMS
Finally, if you want to know anything else about the VMU, the
VMU FAQ at
http://rvmu.maushammer.com/faq.html is an
extremely useful document that explains many common problems, from
how to reset your VMU to animation constraints. However, please bear
in mind that its writing preceded the discovery of self-booting
methods for burning Dreamcast-compatible CDs, so it
doesn't cover any of the self-boot options for
Choosing the Best VMU Games
After you've successfully downloaded a VMU game onto
your memory card, you can access it by removing your memory card from
its berth in the Dreamcast controller. Press the Mode button on the
controller until the playing-card icon flashes, then press the A
button to enter the VMU game.
Please note that you can have only one VMU game on your memory card
at a time, although you can also store multiple Dreamcast
non-minigame saves. The VMU has no multiboot concept; you
can't select between multiple games. VMU games may
use up to 128 blocks (the official maximum), so you also need to
ensure you have enough space, even if the new VMU game writes over
the old one.
However, separating the quality games from the mere demos can be
tricky when it comes to playable VMU titles. Frankly,
it's fun to download everything because the entire
VMU pantheon is limited to tens of titles. You can make your own
decisions then. If you'd like to do that, you might
want to check out the following:
- Rockin B's VMU page
This excellent page has quality ratings for each title, with careful
picks and even screenshots of the better VMU titles. Because
there's no concept of copy protection for VMU
titles, it's very clear which are commercial and
which are noncommercial VMU games. This page has no commercial VMU
titles. See http://www.rockin-b.de/vm/VM-downloads.htm.
- PlanetWeb's VMU site
The people behind the PlanetWeb browser for the Dreamcast still have
their page up. It includes a few VMU minigames and massive amounts of
VMU animations and normal Dreamcast save games, in conjunction with
the fan site Booyaka. Visit http://dreamcast.planetweb.com/vmu/.
- DCEmulation's VMU Games
Although it lumps everything together, this resource has some
interesting VMU games of various kinds, from the sublime to the
ridiculous. Learn more at http://www.dcemulation.com/covers/index.cgi?browse&Vmu%20Games.
If I had to pick some homebrew VMU games you should check out because
they're wacky, weird, cool, or any of the above,
they'd be the following:
- Alien Fighter by Soren Gust
This is an excellent vertically scrolling shooter with sound, a saved
high score, addictive old-school gameplay, and all the bells and
whistles that come with low-resolution black-and-white VMU fun!
- Glucky Labyrinth by Omar Cornut
This game is a fine attempt at a DOOM-style 3D maze game, with chests
to open, levels to ascend, and smooth-scrolling 3D dungeons to
traverse—impressive on such a limited piece of hardware.
- Snaky by Anonymous
This classic game featuring the snake with the ever extending tail
that the player mustn't bump into, is fairly
straightforward but still plenty of fun. It also features a
high-score table for your greatest slithers.
- Minesweeper by Soren Gust
You all probably know and have suffered inadvisable addictions to the
Minesweeper-style game. This is an excellent version, complete with
both sound and save games.
You can download these and others (shown in ) from the Rockin B site.
Figure 1. Title screens
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