Sega Saturn modernization plan

[angelosa]

• VDP1 (needs a full rewrite)

---

• VDP2 cycle patterns
• VDP2 back layer
• VDP2 base NBG2 / NBG3
• VDP2 base NBG0 / NBG1
• VDP2 RBG0 / RBG1
• VDP2 window control (shouldn't need to be in the layer code but postprocessed later)
• VDP2 sprite/shadow control
• VDP2 line control
• VDP2 mosaic control
• VDP2 color calculation
• VDP2 priority (can select per dot ...)

---

• hookup the newly dumped SMPC LLE (is code same for all variants, and region select is done with jumpers?)
• pad bus handling (is a derived MD design)

---

• SH7604 INTC
• SH7604 DMA
• SH7604 SCI
• SH7604 cache

---

• SCSP modernize internal semantics
• Investigate SH-2 to 68k transfers bus penalties, particularly when latter is actually running.

---

• make SCU to be bus aware (.flags?), make sure that the other two DMAs (SCUDSP and SH-2) respect (some of?) these rules.
• concile A-Bus into a single entity (CD-Block HLE, CD-Block LLE, cart slot, floppy controller, MPEG cards, Netlink, ST-V games like fhboxers for serial multicab connections ...)
• replace IOGA functions in ST-V with sega_315_5649_device.

---

• Cleanup hash/saturn.xml, get rid of 2500 lines of unnecessary header repetition;
• Add EGWord redump sets (important given it's the only other keyboard example we will have for a while);

[JimCarlTay]

Known issues (MAME Testers; ST-V):

• MT01657: Graphical issues (diehard, dnmtdeka) (Reported by LastNinja2)
• MT02642: Takes too long to get to game test mode, or to exit from test mode and enter attract mode (myfairld) (From source code)
• MT03864: Music glitches starting to occur during first stage (cotton2, cottonbm) (Reported by abelardator2)
• MT04187: No sound in game, message "SCSP MCIEB enabled ffff" appears (colmns97) (Reported by M.A.S.H.)
• MT04445: Black screen if you choose to play as Jeffry, Sarah, or Wolf (vfremix) (Reported by you)
• MT04446: Incorrectly drawn sprites, or they flash randomly (kiwames) (Reported by you)
• MT06149: Slowdown during quick-time events (diehard, dnmtdeka) (Reported by Solstar)
• MT06270: Freezes occur under certain circumstances (danchih, danchiq) (Reported by izius)
• MT07203: Slowdown when starting a stage after Monarch Bat (batmanfr) (Reported by Planestate)
• MT07417: (Possible) Brief slowdown after one specific fade-out (sandor and clones) (Reported by ICEknight)
• MT07900: (Possible) Crash if argument "-video bgfx -bgfx_backend d3d12" is used when starting in command line (diehard) (Reported by Andrew; I'm not able to reproduce this)
• MT09183: Missing "focus" effect or window sprite layer (sasissu) (Reported by danylopez123)

Known issues (MAME Testers; Saturn console and software list items):

• MT04951: Message "Special Function Code Select enable 0004 0000" appears during opening sequence (saturnjp [azelpantai]) (Reported by Justin Kerk)
• MT06893: Input issues with two multitaps when inserted (Reported by vikbez)
• MT07004: Gray horizontal lines on sprites when flipped (saturn [guardheru]) (Reported by samsho2)
• MT07371: Sprites are glitched out (saturneu [rayman]) (Reported by AnonBaiter)
• MT07507: Crash occurs after Capcom logo (saturnjp [cybots, mshvssf, sfz3, xmvssf]) (Reported by FabricioCoroquer)
• MT07508: Severe graphical glitches (saturnjp [kof96, kof97, samsho3, samsho4]) (Reported by FabricioCoroquer)

Known GitHub issues:

• Make Saturn CD Block implementations to be user selectable #5807 (Attempt to make CD Block implementations user-selectable)

[angelosa]

MT07203: (Possible) Slowdown when starting a stage after Monarch Bat (batmanfr) (Reported by Planestate)

This isn't a "possible", it's a VDP2 fault getting confused between the regular cycle patterns handled naively and the unemulated rotation parameter ones.

MT02642: Takes too long to get to game test mode, or to exit from test mode and enter attract mode (myfairld) (From source code)

Game loves to hang with sound tight loops.

MT07507: Crash occurs after Capcom logo (saturnjp [cybots, mshvssf, sfz3, xmvssf]) (Reported by FabricioCoroquer)
MT07508: Severe graphical glitches (saturnjp [kof96, kof97, samsho3, samsho4]) (Reported by FabricioCoroquer)

These needs testing, I vaguely remember actually playing samsho4?

[JimCarlTay]

Meanwhile, I am currently testing if I can be able to repro MT06149 (slowdown in diehard during quick time events). As of the latest build of PR #15763, I thought it was no longer reproducible, but I'm trying to figure out what changed between the builds I have used prior to test for the sound regression in that game, which is fixed by that PR.

UPDATE: I can still repro MT06149. I've added it back to the list.
UPDATE 2: However, the slowdown as described in that bug is brief as of the last time I tested diehard.

[angelosa]

Will take some performance back from what I'm gonna do tomorrow.
40f6705