The lead developer of the MiSTer’s Saturn core added the last four months’ worth of test updates to the main branch over the weekend, fixing an issue with saving games that’s plagued users for more than a month.
Sergiy “SRG320” Dvodnenko gave a rundown Sunday of what’s new since the last time he updated the main branch in June on his Patreon page.
Updating the main branch makes it easier for MiSTer users to get updates — they can download them by running “update_all” instead of having to grab each new version of the core separately from the “unstable nightlies” channel on the MiSTer Discord server.
For those who don’t use unstable nightlies and only get updates from running update_all, saving Saturn games broke when MiSTer project creator Alexey Melnikov, aka Sorgelig, pushed a new update to the main MiSTer core Aug. 28 that tied into a change to how games are saved in what was the latest “unstable” Saturn core at the time. But that change hadn’t been added to the latest stable Saturn core that players downloaded when using the “update_all” function, since that hadn’t seen an update since June 12.
On Aug. 26, a change to the save index to enable save file selection was committed to a new version of the Saturn core, called “unstable” because it’s essentially still in beta testing. The main MiSTer core was referencing that save index change in the unstable Saturn core, causing saves to break for anyone who hadn’t updated to the latest unstable.
That problem is fixed now that the Saturn core’s been updated on the main branch.
According to the project’s GitHub, these are the updates that have been made since the last time SHIRO! reported on the Saturn core in early September:
- SH7604:
- fix bus access from Slave (Batman Forever: player selection screen)
- fix bus access from Slave DMAC (NBA Action ’98)
- SCU:
- implement reading of Indirect parameters from B-BUS (Hi-Octane (Japan): logo FMV)
- VDP2:
- adjust DISP and Interlace flags latching (Gokujou Parodius Da! regression)
- fix Sprite data color recognition (Pro Yakyuu Greatest Nine ’98 Summer Action: logo)
- optimize code
- adjust DISP and Interlace flags latching (Pro Yakyuu Greatest Nine ’98 Summer Action: green frame glitch)
- SCSP:
- fix Monitor register (NHL All Star Hockey ’98 sounds)
- SMPC:
- implement an open bus (smpctest)
- adjust timing for INTBACK command (smpctest)
- DDRAM:
- move caches to BRAM to reduce LE resources
- rework the time-critical channels (slowdown in VDP1 rendering)
- hide unused channels
- Miscellaneous:
- Recent commit to main changed how some MRA map strings are interpreted
- Change some MRAs to use a version that works for both old and new main
- Update sys
Zet-sensei, who works closely with Dvodnenko to test updates, said last month that new accuracy tests for the SMPC, the System Manager & Peripheral Control chip, were being used to fix emulation of that chip. Two updates in the last month reflect changes made as a result of that test.
The SMPC test as well as tests for emulation accuracy of many other Saturn chips are being made by Celeriyacon, who first became involved in the core last summer when they contributed a sound chip testing tool. As for how Celeriyacon makes the tests, they’ve never said — “very secretive,” Zet-sensei has said.
Other fixes in the last month include fixing MRAs, which are files used when launching ST-V Titan arcade games. The ST-V is the arcade version of the Saturn, almost identical to it except for using cartridges rather than CDs for all but one of its games. The ST-V was broken off of the Saturn core into its own arcade core back in June, but many fixes to the Saturn core also apply to it, so Dvodnenko mentions it in his updates.
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.
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.
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