Log Message:
mame: update to 0.231.

MAME 0.231, our April release, is out now! The Yamaha FM synthesis
rewrite is progressing, with the OPL family (including YM2413,
YM3526, YM3812, YMF262 and Y8950) done this month. A number of
regressions reported against the previous release have also been
fixed. Most things should be improved, but if you notice something
wrong with a system using one of these chips, be sure to let us
know. Warp-1, a very rare Sun Electronics game from the late ’70s,
has been added this month. This is an early example of an “into
the screen” space shooter.

For as long as it has been emulated, the “3D” stages in Contra have
been too easy. This comes down to the functionality of the Konami
007452 chip, which Konami calls a VRC&DMP. Now we know that VRC
stands for Virtual ROM Controller, and controls ROM banking. However,
the DMP part has been more of a mystery, assumed to be some kind
of protection. This month, furrtek worked out that it’s apparently
some kind of Divide/Multiply Processor, for 16-bit maths operations
that would be unacceptably slow on the games’s pair of 6809-family
CPUs. The great news is the game now runs correctly, the bad news
is you’ll probably die a lot more.

David “Haze” Haywood is back this month with fixes for several
arcade games that have never been quite right. He’s fixed graphical
priority issues in SNK’s Beast Busters and Mechanized Attack,
improved timing in Seibu Kaihatsu’s Shot Rider, and corrected layer
offsets in Mitchell’s Funky Jet. He also added support for a couple
of protected Mega Drive bootleg games from Argentina. Recently,
David has been streaming MAME gaming sessions, often highlighting
under-appreciated games. You can watch the recorded streams on his
YouTube channel. Still on the topic of things that have never been
right, sasuke has been busy this month. He’s improved the Nichibutsu
1412M2 DAC playback rate and timer period calculation, most noticeable
on the Mighty Guy soundtrack, and made Taito’s unicycling game
Cycle Maabou playable.