Genesis / Megadrive core ported to MiST

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Re: Genesis / Megadrive core ported to MiST

Postby hyperterminal » Sun Nov 04, 2018 2:50 pm

There is another graphical glitch in the game Turbo Outrun. On the sky you can sometimes see vertical stripes. This is especially visible in stage 4 Indianapolis, when looking at the sun. The US version of OutRunners had a similar bug that was fixed recently.

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Re: Genesis / Megadrive core ported to MiST

Postby Total Eclipse » Sun Nov 04, 2018 9:00 pm

Okay, one somewhat late to the party here,and have only just got around to giving this a try.

One word : Amazing

Thanks to all involved in producing this core.
Atari equipment all in storage - Now playing with MiST :)

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Re: Genesis / Megadrive core ported to MiST

Postby jotego » Mon Nov 05, 2018 8:05 am

Total Eclipse wrote:One word : Amazing

Thanks to all involved in producing this core.


It may sound odd coming from one of developers of the core: but I am amazed myself. Last year I thought it was going to be impossible to have this working on MiST. I actually stopped development of the sound system because I thought the graphics will never catch up. But then, things started moving again. There are many contributors to the core now and Alexey -from Mister- is helping too so rather than a fight between platforms, it looks like we are holding hands moving forward.

I have discovered many interesting games while debugging the core, let me list some of them:

  • Alisia Dragoon: wonderful music
  • Castlevania: Bloodlines: again, great music and a nice introduction to the Castlevania series
  • Kuuga - Operation Vapor Trail: Nice shooter with great music
  • Contra - Hard Corps: the music of this game takes the chip to a new level. Very well produced
  • Crying - Asia Seimei Sensou: Somehow odd graphically, but very interesting music. I need to compare the sound of this game closely with good emulators to see if JT12 is getting it right.
  • Ghouls'n Ghosts: very nice conversion from coin-op, interesting to compare with Anima's version for Atari ST on the choice of colours.
  • Granada: it looks like a low-cost production, but it is very enjoyable.
  • Shadow Dancer: same characters as the coin-op but somehow more enjoyable

I have also been disappointed by some titles, like Xenon 2. How can it be that the Atari ST version has a nicer music in the introduction screen? They used PCM sound on Atari STfm, a system that wasn't even ready for that!

And there were a few disappointments with the system too. There is a good bunch of games poorly produced. Particularly when it comes to sound, there are conversions from arcade that do not handle well moving from an 8-channel YM2151 to a 6-channel YM2612 and cut down on SFX/music more than needed. Again, moving from YM2151 to YM2612 meant adjusting the volume of the FM channels as YM2612 is quieter but some games do not seem to do it so we lose on loudness but also on sound quality because YM2612 drops lower bits of the sound, which YM2151 would have used. Indeed, we could say that YM2612 (Megadrive) is 8-bit sound whereas YM2151 is 16-bit sound.

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Re: Genesis / Megadrive core ported to MiST

Postby DanyPPC » Mon Nov 05, 2018 9:37 am

I'm curious to test the new sound engine.

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Re: Genesis / Megadrive core ported to MiST

Postby ijor » Mon Nov 05, 2018 10:21 am

Sorgelig wrote:Generally Genesis games are not required cycle accurate CPU (except couple demos specifically requiring it). Just because many games have bugs and by different reasons these bugs are hidden/eliminated due to specific place/time the cycle accurate CPU is good to have in Genesis.


Yes, something similar happens on several other platforms. I've seen some cases where bugs are harmless only because an amazing chain of events. Make any small change that breaks that chain, and the bug would become fatal.
Fx Cast: Atari St cycle accurate fpga core

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Re: Genesis / Megadrive core ported to MiST

Postby jotego » Mon Nov 05, 2018 10:37 am

ijor wrote: I've seen some cases where bugs are harmless only because an amazing chain of events. Make any small change that breaks that chain, and the bug would become fatal.


That’s often the case with engineering bugs in real products. They occur/hide because of a chain of events. Someone makes something wrong but depending on the next processing step you may or may not see it. Documentaries about plane crashes show a lot of this.

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Re: Genesis / Megadrive core ported to MiST

Postby slingshot » Mon Nov 05, 2018 11:04 am

jotego wrote:I have also been disappointed by some titles, like Xenon 2. How can it be that the Atari ST version has a nicer music in the introduction screen? They used PCM sound on Atari STfm, a system that wasn't even ready for that!

Well, listen to the PC version then :)

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Re: Genesis / Megadrive core ported to MiST

Postby slingshot » Mon Nov 05, 2018 11:07 am

ijor wrote:
Sorgelig wrote:Generally Genesis games are not required cycle accurate CPU (except couple demos specifically requiring it). Just because many games have bugs and by different reasons these bugs are hidden/eliminated due to specific place/time the cycle accurate CPU is good to have in Genesis.


Yes, something similar happens on several other platforms. I've seen some cases where bugs are harmless only because an amazing chain of events. Make any small change that breaks that chain, and the bug would become fatal.


There's an unfortunate result of this: you cannot make the VDP's timing match the original, because then the imperfect CPU will introduce bugs, but if you cheat a bit in the VDP, then the bugs are working against each other and makes the result acceptable :)

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Re: Genesis / Megadrive core ported to MiST

Postby Sorgelig » Mon Nov 05, 2018 11:25 am

jotego wrote:Ghouls'n Ghosts: very nice conversion from coin-op, interesting to compare with Anima's version for Atari ST on the choice of colours.

comparing to PCEngine version it's poor. I believe it could be better if they would like to. If you compare PCE version with original arcade, then you usually need to spot the differences precisely, while Genesis version is obviously castrated too much.

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Re: Genesis / Megadrive core ported to MiST

Postby seastalker » Mon Nov 05, 2018 9:57 pm

"There are many contributors to the core now and Alexey -from Mister- is helping too so rather than a fight between platforms, it looks like we are holding hands moving forward. "

Perhaps the most beautiful and welcomed sentence I've seen all year, ANYWHERE!! May all cores benefit in the same way!!!

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Re: Genesis / Megadrive core ported to MiST

Postby Higgy » Tue Nov 06, 2018 8:58 am

Hi all,

I was keeping track of the Cores and at the moment we have:

fpgagen_20181101.rbf - old jt12 (0.4?)
fpgagen-titan2.zip - old jt12 (0.4?)

and now there is jt12 v0.5

Do we need to check the problem game ROMS with Core fpgagen-titan2 and if that is ok then the changes in fpgagen-titan2 can be included in fpgagen_201811??.rbf with jt12 0.5 ? Otherwise we could be getting Cores with combinations of jt12 versions etc.

As far as I have looked these seem to be problem ROMS:

Outrunners - sky bug
Gynoug - "Mode7" effect at the beginning of the first level of
Road Rash II - started out perfectly but game froze at the end of race 1.
Shadow Dancer - anyone have an odd glitch from the start of the game where your ninja character and dog are missing frames where they walk comically?
Shining In the Darkness - main town music sounds odd and the percussive instruments take over.
Sonic 1 - music when I completed first stage sounds wobbly.
Adam's Family 1993 - glitching in the underground section
Turbo Outrun - On the sky you can sometimes see vertical stripes. This is especially visible in stage 4 Indianapolis, when looking at the sun

I don't think there have been any comments regarding if fpgagen-titan2.zip is better than fpgagen_20181101.rbf
I will test where I can, but most of my freetime is currently being spent testing a certain pinball game on a certain 8-bit computer :wink:

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Re: Genesis / Megadrive core ported to MiST

Postby DanyPPC » Tue Nov 06, 2018 9:41 am

I can test titan version with Turbo OutRun.

Shadow Dancer and Sonic haven't any problem. They work properly.
I think Sonic runs as on real hardware, reached level 3-3 without any graphic or sound problem.

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Re: Genesis / Megadrive core ported to MiST

Postby DanyPPC » Tue Nov 06, 2018 9:52 am

Turbo OutRun with Genesis Titan2 Core version:
TurboOutRun.jpg
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Re: Genesis / Megadrive core ported to MiST

Postby jotego » Tue Nov 06, 2018 11:03 am

Higgy wrote:Hi all,

I was keeping track of the Cores and at the moment we have:

fpgagen_20181101.rbf - old jt12 (0.4?)
fpgagen-titan2.zip - old jt12 (0.4?)

and now there is jt12 v0.5


Sorry to keep updating... I found and fixed a bug on Scooby Doo yesterday. So now it is jt12 v0.52. Sonic sound at the end of 1st stage seems fine to me, at least with this version.

I am waiting for the Titan 2 demo team to provide a .vgm file so I can check why we miss sounds in their demo. Until then, I do not plan to provide more updates.

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Re: Genesis / Megadrive core ported to MiST

Postby hyperterminal » Tue Nov 06, 2018 12:29 pm

While you are at it, I'd like to remind you of this bug in OutRunners:
Image
As you can see, there is one bad flickering line on the screen of the second player, just on top of it's HUD (it can be best seen if you look above the word "TIME").

This bug only occurs at 31 kHz, so it might be scandoubler related.

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Re: Genesis / Megadrive core ported to MiST

Postby Total Eclipse » Tue Nov 06, 2018 3:35 pm

The only thing I've found that completely fails so far is the Stuck Somewhere In Time demo. That reports that it's being run in an emulator, presumably due to checking CPU timings?
Atari equipment all in storage - Now playing with MiST :)

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Re: Genesis / Megadrive core ported to MiST

Postby slingshot » Tue Nov 06, 2018 4:14 pm

DanyPPC wrote:Turbo OutRun with Genesis Titan2 Core version:
TurboOutRun.jpg

Turbo Outrun sky is bad. But at least it's not a new bug, it was there even in September.

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Re: Genesis / Megadrive core ported to MiST

Postby DanyPPC » Tue Nov 06, 2018 5:38 pm

Yes, i know. That was only a test for Higgy.

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Re: Genesis / Megadrive core ported to MiST

Postby Nemmerle » Thu Nov 08, 2018 3:12 am

It seems I always reach the cool projects when things are advanced and I have nothing more to add.

This Mega Drive FPGA emulation sounds awesome to me. I started to googling MISTer adn MIST, I was really thinking in buying one ... but I gave up.

I am more a Xilinx guy, so I think I will try to get your code and try to implement something in a Xilinx Zynq. I have here a Zynqberry with a 7010 that I will use to test things.

I can't promise anything, buy in the case I can finally port this core and emulate something in my Zynqberry, I will let you know.

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Re: Genesis / Megadrive core ported to MiST

Postby vebxenon » Thu Nov 08, 2018 6:50 am

Sorgelig wrote:
jotego wrote:Ghouls'n Ghosts: very nice conversion from coin-op, interesting to compare with Anima's version for Atari ST on the choice of colours.

comparing to PCEngine version it's poor. I believe it could be better if they would like to. If you compare PCE version with original arcade, then you usually need to spot the differences precisely, while Genesis version is obviously castrated too much.


There's no Ghouls'n Ghosts for PC Engine. It was done for Supergrafx, which has more advanced hardware https://en.wikipedia.org/wiki/PC_Engine_SuperGrafx. Ghouls'n Ghosts for Mega Drive was reprogrammed by Sega and one of the first games for the system. It was also released on Master System.
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Re: Genesis / Megadrive core ported to MiST

Postby Sorgelig » Thu Nov 08, 2018 8:20 am

vebxenon wrote:There's no Ghouls'n Ghosts for PC Engine. It was done for Supergrafx, which has more advanced hardware https://en.wikipedia.org/wiki/PC_Engine_SuperGrafx. Ghouls'n Ghosts for Mega Drive was reprogrammed by Sega and one of the first games for the system. It was also released on Master System.

SuperGrafx capability is roughly on par with Genesis. Original TurboGrafx had only only one scrolling plane. SuperGrafx adds second one. Genesis already has 2 planes + window plane which can be considered as 3rd plane. Overall somewhere SuperGrafx is better, somewhere Genesis is better. No much advantage of one over another.

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Re: Genesis / Megadrive core ported to MiST

Postby slingshot » Thu Nov 08, 2018 9:25 am

DanyPPC wrote:Yes, i know. That was only a test for Higgy.


Found the problem with Turbo Outrun, I wonder what the fix will break. Seems a H-INT should happen after the last active line (or the beginning of the first inactive). It counts the interrupts, and if one less happen, line no. 1 instead of 0 will replicated at the top positions.

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Re: Genesis / Megadrive core ported to MiST

Postby DanyPPC » Thu Nov 08, 2018 9:38 am

Good !

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Re: Genesis / Megadrive core ported to MiST

Postby slingshot » Thu Nov 08, 2018 12:37 pm

Nemmerle wrote:It seems I always reach the cool projects when things are advanced and I have nothing more to add.

This Mega Drive FPGA emulation sounds awesome to me. I started to googling MISTer adn MIST, I was really thinking in buying one ... but I gave up.

I am more a Xilinx guy, so I think I will try to get your code and try to implement something in a Xilinx Zynq. I have here a Zynqberry with a 7010 that I will use to test things.

I can't promise anything, buy in the case I can finally port this core and emulate something in my Zynqberry, I will let you know.


There are other cores, which should benefit from some care.
Seems this 7010 is a good candidate, it has 2,1 MB of block RAM, VRAM and the 68k RAM can be implemented in it. (the only thing I miss from the Cyclone III, some more BRAM). Maybe you could port the MiSTer version, it also uses BRAM for VRAM and 68k RAM, and DDR3 SDRAM for the ROM.

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Re: Genesis / Megadrive core ported to MiST

Postby phoboz » Thu Nov 08, 2018 12:55 pm

Nemmerle wrote:It seems I always reach the cool projects when things are advanced and I have nothing more to add.


Support for interlace graphics mode (320x448i) is still a major missing function of this core, so this is a major task to undertake (if you want :?: )


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