Arcade / Console --> Amiga conversion discussions
 

Basically, CPS games have extremely made game code in 68k, with many ideas and things never implemented on an Amiga.

Always the same burden : 1) the ram needed, 2) the CPU takes care of the game logic, and is sending all the time tiles metadata to the chips, which has to be replaced by blitter routines (and sprites).

That's why the 68000 is clocked either at 10 or 12mhz.

Ghouls'n'Ghosts also run at 60fps. what i saw until now on STE is certainly not 60fps, but 25 fps. And it works very well.

I did a research about SSF2T. Basically, the 1200 version has everything ! The problem is that they never removed the PC routine that the coders have added : it forces the game to run @ 60fps at any cost (absolute), instead of automatic screen refresh (relative fps display).

Even at 30fps, SSF2T would have been great, with all the animations running, sound, music and sprites.

A 6 buttons joystick can be used on Amiga. What's the problem ?

on A1200 with 2mb would be possible

CPS games use unified code, and unified assets.

2mb would be only for a computer with tile hardware. With no tile hardware, you need 4mb (count also the conversion of the music and sfx, taking quite an amount of ram space).

we did great with rygar, who knows...;)

I think you vastly overestimate the requirements. Keep in mind that the Amiga version would use reduced graphics and sound (fewer colours, 8 bit samples).

You can also load stuff off disk when required so no need to keep it all in RAM.

The main problem with SF2 is that the sprites are massive and everything very colourful. The blitter just isn't fast enough to use 256 colour modes... Maybe 32 colours, but it gets tricky because you actually have four palettes you need to manage:

1. Character 1
2. Character 2
3. Background
4. Health/time display

The first three can be different every time.

The blitter speed is the real limitation on the Amiga. It's why so many games use 16 colour modes, or dual playfield. The Amiga's sprites are rarely used for actual sprites, instead being either for status displays or an extra layer of parallax.

The best games work within those limitations. Using the separate sprite palette and the copper you can get a lot of colours on screen and really effectively hide the limitations, but you need to design the game with that in mind from the very start. Arcade ports are obviously designed for CPS2 hardware.

If we reduce sprites size, and use copper like you've said, we can manage to do well. On A1200 we can use 020 with blitter to speed up operation. Maybe we "only" well use 64 colors, we can have 50 hz conversion!

I'm afraid that even with reduced graphics (i.e. 16 colours) you will need more memory to store the sprites and other assets. I would estimate that the reduced graphics data still requires about twice as much memory compared to the arcade machine. So the real problem here is the design of the Amiga graphics system.

Well, once you get over 16 colours you need more cycles for bitplane DMA... And of course some of the extra colours are shared with sprites.

The problem with reducing the sprite size is that you need to fix all the hit boxes and movement speeds, it gets complex and the game won't play quite like the arcade version.

That doesn't make any sense... Why would the Amiga graphics need more memory than the arcade ones? The arcade system has a huge memory mapped ROM for graphic data, which becomes RAM on the Amiga.

The problem Anima stands with the bitplans number.... CPS games use something like 8 bitplans in Amiga mode (considering that the CPS systems are planar to start with).

If the arcade needs 16mb (Ghouls'n'ghosts to name it), with only 16 colors, you lower the bar for the graphics storage.

For Ghouls'n'Ghosts STE, you will need 4mb of ram even with 16 colors for the whole game, also considering the amount of sprite frames and the diversity of the tiles for the whole game.

Ghouls'n'Ghosts should be working good on A500 with 4mb of ram (more if 32 colors mode is used), and in 64 or 128 colors on A1200.

I say this considering what you have achieved until now on STE on GNG.

Even in 30 fps, SF2 would still be great to play. 60 fps is just pure delirium to achieve, the Amiga even the AGA machines just don't have the grunt for this.

Imagine, a PC with 486DX2 just could not have a way to make SSF2T running at 60 fps. That's why gametek PC coders had to insert a routine to fix the VBL @60fps. Otherwise, they explained the game never could have been running on PC.

Next the sprites size is not a problem. At all. Anima just got Shielder, the 1st level boss of Ghouls'Ghosts perfectly animated on a plain STE in 16 colors.

CPS Game doesn't work the way usual ST and Amiga games do. It's basically a print and display engine.

The real hard thing is to refresh the tiles needed for sprites and background per VBL. The CPU has to work overtime to put these out.

You should check Anima's test with arcade Final Fight, the huge sprites can move all together on the screen.

Isn't also the main problem here that the stupid Amiga can only access 2MB of RAM for graphics, sound and stuff? So if you have Fast RAM, I guess it can be used as temp storage and you have to bank it/swap it with Chip all the time, or something, but it's inconvenient and I am sure introduces a huge performance problem.

Whereas the ST has only one type of RAM and it can use it all for whatever. I think that probably creates an advantage for the ST.

You get back to the : "you need to split every sprites asset and levels assets".

that's what it is.

Or else, you go for a software renderer and you use fast ram to get the maximum speed out of the 68000.

It's so stupid to have memory this way, why was it even made like that? Is this the only machine that uses memory in this way?

it's only a problem depending on the way you want to code on the amiga.

In fact, one great way to port CPS game would be to use the cartridge port.
It use up to 8mb of rom :) And it's directly connected to the 68000 processor.

Yeah but that leaves out all the people that don't have an A500.
It would be great to have cartridge games, though. I would definitely be interested inn that, and always wondered why it never happened.

Because otherwise your fast RAM would be as slow as your chip RAM.

Or you only get half as many colours, like the ST.

Or you do something even stupider, like the Sega consoles, and entirely separate your graphics memory from your CPU.

I see, speed considerations I have not had. But why is it capped at 2MB? Would have been nice to add an option to expand both.

Hmm that's the MSX way of working too, actually, all computers today have separate graphics memory, so, I guess it has been deemed it isn't that stupid ;)

those 2mb of chip could be soupped up to more maybe (@Toni can you confirm or negate what i said ?)

the 68000 is able to support 16mb of ram (Fast-ram).

however, it's clear that with a new board that you could clip over the chip ram, in order to bring it to 16mb of chip....I'm maybe dreamin' :D

It's not as though 2 MB is a particularly low cap when you consider that all Amiga graphics cards, intended to use much bigger screens, are capped at 4 MB. A contemporary PC graphics card had something between 768 kB and 2 MB. Given the total addressable space of a 68000 or 68EC020 (8 MB fast), it was also well-rounded.

The access from CPU to graphics memory is much faster on today's PC than it was on the MSX or Sega, where access to graphics memory was so slow that you couldn't dream of drawing bitmapped graphics. The Amiga approach is more general, as much of the Amiga's hardware is, at the cost of being uncompetitive with "idiot savant" technology.