CPC+ color palette

[freemac]

Hi,

In CPC 6128 we have "only" 27 colors
I ask about using more color in CPC+, does it just change a 27 colors palette ?
In other way can I theoricaly hack for sample super cauldron ?
~in this way I can hack only one CPC+ game, show me the best choice

[andycadley]

It doesn't change the 27 colours in the "old" palette. If you set any colour using the "old" palette mechanism it re-writes that to the relevant fixed RGB value and stores it in the ASIC palette registers.

To select from any of the 4096 colours available you have to use the "new" method instead, which is basically:

Page in the ASIC registers at #4000
Write the relevant values to the appropriate ASIC register
(Optionally) Page out the ASIC registers again

How difficult that is to patch into any given game depends a lot on how it works. If the code is running (or has to access data) from #4000 to #7fff then you may have to relocate it or use a springboard function elsewhere so that the ASIC doesn't get in the way. In addition you're going to need at around twice as many bytes to store colours (unless they're fixed throughout).

For anything that changes the palette dynamically you also need to consider that changes to the Plus palette registers are (unfortunately) not atomic so you will potentially see a glitched colour if you change it at the point where that colour is on-screen.

[robcfg]

The CPC classic has a palette of 27 colours, of which it can show 16 on Mode 0, 4 on Mode 1, and 2 on Mode 2. Any of the 27 can be used as border colour.

Now, the CPC+ have a palette of 4096 colours while having the same limitations per Mode. Then you have the sprites which I don't remember if they use their own palette entries.

What is it exactly you are trying to do?

[andycadley]

Then you have the sprites which I don't remember if they use their own palette entries.

Yes, the sprites have a separate palette of 15 possible colours. 

[arnoldemu]

Do you want to hack a CPC game to give it Plus palette on Plus?

Do you want to give CPC extra colours without making Plus implementation in FPGA?

What is your goal?

[GUNHED]

Hey guys, don't want to be nitpicking, but please call the two computers either CPC464/CPC6128 or 464plus/6128plus. Or simply CPC or Plus if you prefer. There is no CPCplus or such a thing. 

[ZorrO]

There is no Gunhed or such a thing. 

[freemac]

How do I create a forum vote ?

I think around retro-compatible game (ones running on Amstrad CPC 6128 and also CPC 6128 plus)
I think super cauldron is this case, and also Prehistorik.
Here I want just a list of game retro-compatible. And vote for just one of them.

[ZorrO]

Select section in which you want to post survey and instead of [NEW TOPIC] button, just click [NEW POLL].

[freemac]

or else a C64 palette 

[andycadley]

I'm confused by the poll, Super Cauldron and Saboteur weren't ever Plus games, whereas Prehistorik II was (although I'd argue it was a CPC game with some extra bolt on Plus features, rather than a Plus game downgraded to the older models)

[arnoldemu]

Freemac are you planning hardware enhancement for all CPC or only for your CPC in a FPGA?

Is it an enhancement for all Gate-Array or only palette?

Would it be compatible with Plus? 

Is the palette fixed and I can choose a theme (e.g. CPC standard, Orange, C64) or fully programmable? 

is it like these but for CPC?

https://zxdesign.itch.io/ulaplus



Is it a special mode for CPC like in Aleste 520EX which can give 64 colours?
https://www.cpcwiki.eu/index.php/Aleste_520EX

Or do you ask for some games to have Plus palettes added to enhance the games?

If you do see this list here of games already done:

https://www.cpcwiki.eu/index.php/Converted_GX4000_Software

Most have had controls updated for gamepads and 2 buttons, many also have new palettes.

[freemac]

In fact I have a 4th VGA palette mode free (color, green, orange, <another ?>)
First I think a special fixed palette for only one game

But then I think now that C64 palette shall unlock more games (adapted from C64 (16 colors, perhaps I have just to "cut" 3 wires for doing that easy))

I think (color, green, orange, C64) shall be cool 

[arnoldemu]

In fact I have a 4th VGA palette mode free (color, green, orange, <another ?>)
First I think a special fixed palette for only one game

But then I think now that C64 palette shall unlock more games (adapted from C64 (16 colors, perhaps I have just to "cut" 3 wires for doing that easy))

I think (color, green, orange, C64) shall be cool

It would be interesting to see how that would work and if it would work for multiple games. I think best for that is to convert each 27 colour to similar on c64. There will be repeats but no program would need to be changed. Maybe this works well maybe not and good to experiment I guess.

Another might be to take the 27 colours and adjust how vibrant they are and maybe reduce colour a bit, that could work with lots of games.

You may find a fixed palette per game is best choice and gives the best look, again this would be at the gate-array in your FPGA where one of the 27 colours chooses a colour in your special palette