MAME is a multi-purpose emulation framework.
MAME's purpose is to preserve decades of software history. As electronic technology continues to rush forward, MAME prevents this important "vintage" software from being lost and forgotten. This is achieved by documenting the hardware and how it functions. The source code to MAME serves as this documentation. The fact that the software is usable serves primarily to validate the accuracy of the documentation (how else can you prove that you have recreated the hardware faithfully?). Over time, MAME (originally stood for Multiple Arcade Machine Emulator) absorbed the sister-project MESS (Multi Emulator Super System), so MAME now documents a wide variety of (mostly vintage) computers, video game consoles and calculators, in addition to the arcade video games that were its initial focus.
IMPORTANT NOTE: The CHD format has undergone a change with this release. The main reason for this change is to include some of the key metadata into the hashes for the CHDs. This ensures that the metadata is valid and prevents abuse.
The first impact you will find is that all of your CHD differencing files are invalid. Just delete your "diff" directory contents entirely.
The second impact is that all your existing CHDs will warn you that they have incorrect hashes. This is expected. Your old CHDs should still work fine, so if you can live with the "bad ROM" warnings, you don't really need to do anything. However, if this bugs you or you want to be "clean", you can update your CHDs, using this command line:
chdman -update <chdfile> <newchdfile>
for each one of your CHDs. This will take a while, but will produce CHDs that match the new checksums posted in the drivers.
Ok, we are on the home stretch now. Thanks to Phil Bennett, most of the major problems of the last few versions have been cleaned up. This should be the last update before we release 0.130, so make sure you get your bug reports into MAMETesters as soon as you can to help ensure this is a good release!
Still cleaning up the big device-ification mess from last version. Most all reported bugs are fixed now, so hopefully we are on the home stretch. Please grab the latest 0.129u5 update and verify that everything you care about is working fine and playing sounds as expected. And while you're at it, try out a few games you don't care about. Who knows, you might discover something new!
Once again, please report all issues over at MAMETesters to ensure they get proper attention. You will notice the large list of fixed bugs at the top of the whatsnew.txt. If it's not reported, don't assume we know about it!