From ceb582b8a0df2b8c0119872127fba3cdc0334b04 Mon Sep 17 00:00:00 2001 From: Vas Crabb Date: Fri, 20 Oct 2023 17:57:18 +1100 Subject: docs: Updated for changes to media loading behaviour. Bumped docs version since this now describes behaviour of the upcoming release. --- docs/source/conf.py | 4 ++-- docs/source/usingmame/aboutromsets.rst | 24 +++++++++++++++++++++--- docs/source/usingmame/assetsearch.rst | 18 +++++++----------- 3 files changed, 30 insertions(+), 16 deletions(-) diff --git a/docs/source/conf.py b/docs/source/conf.py index db6ec89301d..5a8c585f694 100644 --- a/docs/source/conf.py +++ b/docs/source/conf.py @@ -63,9 +63,9 @@ copyright = u'1997-2023, MAMEdev and contributors' # built documents. # # The short X.Y version. -version = '0.259' +version = '0.260' # The full version, including alpha/beta/rc tags. -release = '0.259' +release = '0.260' # The language for content autogenerated by Sphinx. Refer to documentation # for a list of supported languages. diff --git a/docs/source/usingmame/aboutromsets.rst b/docs/source/usingmame/aboutromsets.rst index 51c72d0ce41..3a5197a3159 100644 --- a/docs/source/usingmame/aboutromsets.rst +++ b/docs/source/usingmame/aboutromsets.rst @@ -68,6 +68,24 @@ If you hit problems with a set not working, there are several things to check-- ROMs and CHDs ------------- -ROM chip data tends to be relatively small and gets loaded to system memory outright. Some games also used additional storage mediums such as hard drives, CD-ROMs, DVDs, and Laserdiscs. Those storage mediums are, for multiple technical reasons, not well-suited to being stored the same way as ROM data and won't fit completely in memory in some cases. - -Thus, a new format was created for these in the CHD file. **Compressed Hunks of Data**, or CHD for short, are designed very specifically around the needs of mass storage media. Some arcade games, consoles, and PCs will require a CHD to run. As CHDs are already compressed, they should **NOT** be stored in a ZIP or 7Z file as you would for ROM images. +ROM chip data tends to be relatively small and are loaded into system memory in +their entirety. Some games also used additional storage media such as hard +disks, CD-ROMs, DVDs, and LaserDiscs. Those storage media are, for multiple +technical reasons, not well-suited to being stored the same way as ROM data and +won’t fully fit in memory in some cases. + +Thus, a new format was created for these in the CHD file. **Compressed Hunks of +Data** files, or CHD files for short, are designed very specifically around the +needs of mass storage media. Some arcade games, consoles, and PCs will require +one or more CHD files to run. As CHD files are already compressed, they +**should not** be stored PKZIP or 7-Zip archives as ROM images would be. + +To save space when multiple variants of a system or software item are present, +MAME supports *delta CHD* files. A delta CHD file only stores the parts of the +data that differ from its *parent CHD* file. This allows large space savings +when different variants share a lot of data. Delta CHD files can only be used +for clone systems, devices with a parent ROM device, and clone software items. +A delta CHD file must use a (non-delta) CHD file from the parent system, parent +ROM device or parent software item as its parent CHD file. The parent CHD file +must be present to use a delta CHD file, or MAME will not be able to read the +shared data from it. diff --git a/docs/source/usingmame/assetsearch.rst b/docs/source/usingmame/assetsearch.rst index 102e87c9bbd..325d4bcfd7e 100644 --- a/docs/source/usingmame/assetsearch.rst +++ b/docs/source/usingmame/assetsearch.rst @@ -227,10 +227,6 @@ item ROMs in the following locations: * A folder or archive matching the short name of the parent software item, if applicable. (This is for convenience for software items that also run as stand-alone systems with the same short name, such as Neo Geo games.) -* Any folders and archives that would be searched for system or device ROMs for - the system or device that the software list belongs to. This is for - historical reasons due to the way software list support was originally added - to MESS and will be removed in a future version of MAME. If you load the German version of Dune II from the Mega Drive/Genesis cartridge software list in the PAL Mega Drive console, MAME will look for the cartridge @@ -255,13 +251,6 @@ ROM as follows: * Still ignoring the short name of the software list, MAME will use the short name of the parent software item only, looking for a folder called **dune2**, a PKZIP archive called **dune2.zip** or a 7-Zip archive called **dune2.7z**. -* The short name of the PAL Mega Drive system is ``megadriv``, so MAME will look - for a folder called **megadriv**, a PKZIP archive called **megadriv.zip**, or - a 7-Zip archive called **megadriv.7z**. -* The parent system of the PAL Mega Drive is the North American Genesis system, - which has the short name ``genesis``, so MAME will look for a folder called - **genesis**, a PKZIP archive called **genesis.zip**, or a 7-Zip archive called - **genesis.7z**. CHD format disk images ~~~~~~~~~~~~~~~~~~~~~~ @@ -284,6 +273,13 @@ almost the same way it searches for ROMs, with just a few differences: file itself. The checksum of the CHD file itself can vary depending on compression options. +To save space, MAME allows delta CHD files to be used for clone systems, devices +with parent ROM devices and clone software items. The delta CHD file must use a +CHD format disk image from the parent system, parent ROM device or parent +software item as its parent CHD file. The space saved depends on how much +content can be reused from the parent CHD file. MAME searches the same +locations for parent CHD files that it would search for the disk image itself. + Loose software ~~~~~~~~~~~~~~ -- cgit v1.2.3