The VMU, initialism of Visual Memory Unit (called VMS peripheral for t
Visual Memory System in Japan or Virtual Memory Unit), is a memory card Sega Dreamcast. While its most basic function is as a removable storage device the VMU may also serve as an auxiliary display during normal gameplay and, through use of additional software, act as a handheld game console. Console-like features of the VMU include a small black and white screen, speaker, directional pad, and four buttons.
Several titles for the Dreamcast included mini-games that could be downloaded onto a VMU. The Sonic Adventure series, for instance, included the Chao Adventure mini-game. In the g
ame players could transfer Chao eggs to the VMU and play to increase the stats of their hatched Chao, whereupon they could upload their improved Chao back into the Dreamcast game.
The VMU is plugged directly into one of two slots on a Dreamcast controller. Two VMUs may be plugged in each controller. When operated independently of the Dreamcast console, the VMU acts as a file manager with limited game console functionality. VMUs may also connect to each other directly to facilitate file transfer or multiplayer gaming.
use the player is prompted to select from a group of simple bitmap images to serve as the default background for the VMU. This image is displayed while the Dreamcast console is in the operating system menu; it is usually replaced by a simplified logo during regular gameplay. Some titles display custom animations on the VMU's screen during gameplay, while some titles also offer new background images for the unit.
The VMU runs on two CR-2032 lithium batteries which are inserted into the rear of the VMU under a screw-secured lid. Without battery power, the VMU still works as a memory card and auxiliary display, but cannot play downloaded mini-games.