ST-V Titan Splits Off the Saturn Core on MiSTer

The Saturn MiSTer core has lost ST-V Titan functionality — because it was split off into its own separate core.

The split Feb. 24 signifies how mature the ST-V emulation has become since developer Sergiy “SRG320” Dvodnenko initially added support for it in late January. The move also frees up some space for the main Saturn core, as the MiSTer FPGA only has so many transistors for emulating hardware.

The ST-V Titan is essentially an arcade version of the Saturn with a few differences such as running games of cartridges instead of CDs — with the exception of one fishing game that uses a disc — and having a couple arcade vendor test modes.

Neither the new ST-V core nor the most recently updated Saturn core have been added to the main MiSTer branch yet, so they must be manually downloaded from the official MiSTer Discord server’s unstable nightlies channel.

While the unstable nightly Saturn core simply needs to be put into your MiSTer’s “consoles\cores” folder, the process needed for ST-V games is a bit more complicated. Courtesy of Robby in the MiSTer Discord, here are the steps for manually installing the ST-V core and the MRA files needed to play ST-V games:

• Download latest single or dual sdram ST-V core here
• Copy the ST-V core RBF to \media\fat\_Arcade\cores and name it “ST-V.rbf”
• Download latest MRAs here
• Extract the ST-V MRA folder to \media\fat\_Arcade
• Acquire your own stvbios.zip (from 0.258 rom set or later) plus ST-V MAME ROMs and add them to \media\fat\games\mame
• Launch any ST-V MRA to play a game.

Arcade cores on the MiSTer use MRA files to launch their games. As Birdybro explained on the MiSTer Discord, “they describe to the main MiSTer binary how to load the ROM parts into DDR3 or SDRAM, and various other things.” He said it’s because the MAME format is usually a ZIP file for the arcade game and a bunch of files inside representing each of the different mask ROMs on the board.

To simplify keeping all the necessary files up to date, Davewongillies made a script to update the ST-V core and its MRA files that can be downloaded from this GitHub page.

While the core split was the biggest news since SHIRO! last reported on them Feb. 14, a lot of improvements have been made to performance since then, too. As listed on the cores’ GitHub page, those updates since then are as follows:

• SH7604:
  • fix 16-byte transfer mode in DMAC (Die Hard Arcade ST-V)
• SCU:
  • fix DMA reading CBUS with an unaligned address (Advanced V.G.: cutscene freeze)
  • fix the decrement of the DMA read counter (Street Fighter Zero 3 regression)
• VDP1:
  • fix Gouraud shading for normal sprite (Manx TT SuperBike: menu regression)
  • fix the sprite rendering (Asuka 120% Limited Burning Fest LimitOver: timer)
  • fix Vblank Erase (ST-V Virtual Mahjong 1/2)
  • optimize Gouraud shading divider
  • fix the normal sprite rendering (Columns 97 regression)
  • fix timing of reading the framebufer (Grandia: items menu)
  • re-fix timing of reading the framebufer (Sega Ages/Akumajou Dracula X regressions)
• VDP2:
  • fix reading coefficient table for rotation scroll screen (Panzer Dragoon Saga: name entry screen)
  • fix the calculation of the address of coefficient table (Panzer Dragoon Saga: horizon line)
  • fix the usage of Scale coefficient for Rotation scroll screen (Astal: fog)
• SMPC:
  • fix break condition for INTBACK command (fix buttons for some ST-V games)
• Miscellaneous:
  • add horizontal crop option to hide artifacts
  • fix hcrop
  • improved h/v offset (CRT)
  • add swap joystick option
  • fix the wheel, add dual mission stick support via SNAC
  • fix case of some paths
• ST-V:
  • add channel for loading eeprom
  • implement 315-5838 decompression chip (Decathlete)
  • use PORTA.3/PORTB.3 as Button1 (Batman Forever)
  • rearrange the buttons
  • add analog h/v offset
  • implement 315-5881 decompression chip (Astra Superstars, Elandoree, Final Fight Revenge, Radiant Silvergun, Steep Slope Sliders, Tecmo World Cup ’98, Tecmo World Soccer ’98)
  • implement RAX sound board (Batman Forever)
  • add special button mapping for Batman Forever

Despite the ST-V’s similarity to the Saturn, its versions of games that were ported to the home console do exhibit differences — often for the better. Toya on the MiSTer Discord compiled a rundown of some of the games’ ST-V versions when compared with their Saturn ones:

Groove On Fight

-   Higher resolution graphics with better sprite detail.
-   Faster gameplay with no slowdown or input lag.
-   Instant transitions between rounds (Saturn has loading times).
-   Saturn version has extra characters, but the trade-off is lower performance.

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Radiant Silvergun

-   Better sprite clarity and smoother animations.
-   No load times vs. Saturn version.
-   Some sound effects were compressed on Saturn.
-   Saturn version has an extra mode (Story Mode) but is slightly slower in spots.

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Cotton 2

-   Better enemy sprite clarity and less sprite flickering.
-   Smoother scrolling and performance.
-   Saturn version has minor slowdown in busy scenes.
-   Load times exist on Saturn but not on ST-V.

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Cotton Boomerang

-   Faster gameplay speed compared to Saturn.
-   Saturn version has loading times before levels.
-   Smoother frame rate on ST-V.

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Final Fight Revenge

-   Saturn version is slightly slower due to hardware limitations.
-   ST-V has smoother frame rates and no loading screens.
-   Sound quality is better in ST-V.

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Shienryu

-   Arcade version has better colors and sharper visuals.
-   Saturn version has slight sprite compression.
-   Minor slowdown on Saturn in busy scenes.
-   Load times exist on Saturn but not on ST-V.

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Astra Superstars

-   More fluid animation.
-   Faster and smoother combat.
-   Saturn version has frame skips and minor slowdown.
-   Loading between fights on Saturn.

Dvodnenko first released a playable build of the core to the public in May 2022 and has updated it many times since then. It was first added to the main MiSTer branch in October 2023, indicating that it was mature enough to be available to all MiSTer users rather than as an optional core that had to be added manually. The last time its updates were pushed to the main MiSTer branch was in January.

Anyone interested in supporting Dvodnenko can do so at his Patreon.

The MiSTer is a field-programmable gate array, a chip that can be changed by programming it to physically emulate retro video game consoles. It includes an SD card reader from which “cores” and games can be loaded.

The cores are the programming that tells the FPGA chip how to configure itself to reproduce the performance of a console. There are cores for a wide array of consoles, from the Atari 2600 to the PlayStation — and, of course, the Saturn.