Technical information

SEGA Confidential
SATURN Virtual CD System User's Manual
15
Files that Contain Unaltered CD Images
CDs have a variety of format standards. Data edited in formats and lengths that
meet those standards are saved as “CD Image Files”. The VCD emulator sends these
CD image files directly to the VCD I/F Board. In order to do this, the CD image
must be created before the emulation is started. This is called "Real-Time" emulation
mode.
In this emulation mode, actual complex sector placement (arrangement), such as
channel interleave is performed prior to the start of emulation; therefore, there are
no functional restrictions as those previously referred to in “Direct DOS File Access.”
CD Images and Data Files Used for Partial Updates
This emulation mode uses a single updated data file, and enables an emulation test
using the original CD image file. This is called the "Partial CD Image Update" emu-
lation mode. The VCD emulator determines the type of emulation to run based on
which files are present when it is started, and on the parameters of the VCD emula-
tor startup command options. File extensions are used to determine whether the
necessary files exist to run an emulation. The body section is specified by the param-
eters of the VCD emulator startup line options.
The CD emulation software consists of four programs: the VCD emulation program
and three preprocessing programs.
• VCDEMU.EXE is the program that performs VCD emulation.
• VCDPRE.EXE is the program that performs preprocessing before direct DOS emulation is performed.
• VCDBUILD.EXE is the program that performs preprocessing before real-time emulation is performed.
• VCDUTL.EXE is the program that performs preprocessing before partial CD image update emulation
is performed.