Saturn MiSTer Core Gets First Update in Five Months, Adds Expanded RAM Support

A five-month wait for owners of the MiSTer FPGA ended this week when the hardware emulator’s Saturn core got its first update since November.

Developer Sergey Dvodnenko, aka SRG320, published new code Monday on his Github that makes a litany of improvements to his core’s performance. His Patreon page listed fixes for emulation of the CD-ROM drive, both VDP graphics processors and the SCU co-processor. It also denotes that the core supports the 1 MB and 4 MB expanded RAM cartridges — aka DRAM — for the very first time.

The updates include:

• CD:
  -rework cd drive interface (Main module)
  -add fifo logic for “Put sector data” command (Sega Ages Volume 1)
  -fixes for SH7034
• CPU:
  -fix wait logic in SH7604 DIVU
  -fix reset in SH7604 peripheries
• VDP1:
  -fix draw end flag (Worldwide Soccer ’98)
  -fix table jump to unaligned link (Akumajou Dracula X – Gekka no Yasoukyoku)
  -fix IO writing to FB (Valora Valley Golf)
  -add support for End Code for Normal/Scaled sprite (Primal Rage)
• VDP2:
  -fix burst write to VRAM (Shining Wisdom)
  -fix window in hires mode (Pro Pinball The Web)
  -fix fetch Back Color (Rampage – World Tour)
  -fix Field flag (True Pinball)
  -add support Screen-over for Rotation scroll screen (Virtua Fighter game series, Fighting Vipers)
  -fix line scroll in interlace mode (DecAthlete, Astra Superstars)
  -fix Rotation parameters window and pipeline (Azel – Panzer Dragoon RPG, Bulk Slash)
  -fix coefficient data transparent bit (Grandia)
  -fix IO reading from CRAM (Death Throttle)
  -fix pattern name parameters for reduce/expand (Rabbit)
• SCSP: fix DMA end flag (Sega Ages Volume 1)
• SMPC: fix INTBACK command (Theme Park ,Worldwide Soccer ’98)
• SCU:
  -fix DMA write
  -fix BBUS read/write (Virtua Fighter)
  -add DMA write to ABUS (Street Fighter Zero 3)
• Add full size VDP1 framebuffer memory (Burning Rangers, FIFA – Road to World Cup 98)
• Add support for DRAM cartridge.

The latest version of the core, which comes in two versions for one or two sticks of RAM, can be downloaded from the “unstable nightlies” channel on the MiSTer Discord server. It also requires users to run the unstable main MiSTer build that was posted to that channel March 26.

Awbacon, who runs the Video Game Esoterica YouTube channel, put together a video Tuesday showing off how the new core performs with a few games, including Castlevania, Twinkle Star Sprites and Gungriffon II. His video also gives instructions on installing the core for those who need a little help with that.

Users on the MiSTer Discord server reported games like Street Fighter Zero 3 and Vampire Savior, which both require the 4 MB expanded RAM cartridge, running well. Other games showed improvements, like Bulk Slash displaying skyboxes, Panzer Dragoon Zwei playing sound and Last Bronx running at full speed.

During the five-month wait for a core update, some worried about Dvodnenko’s wellbeing, as he lives in Ukraine amidst an ongoing war with Russia.

Those fears were allayed somewhat when he posted a brief update Feb. 13 to his Patreon to say that he was working on fixing a “significant problem” in the CD block and to ask for patience.

It was the first sign of life from him since he updated the core Nov. 16, which Shiro reported on at the time.

Dvodnenko released to the public a playable build of the Saturn core for the first time in May last year, with a flurry of updates coming between late September and mid-November.

If you’re interested in supporting Dvodnenko, check out 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 now, at least in an early form, the Saturn.