Re: [hatari-devel] TT palette bankswitching should be supported

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Ah, so this isn't about ST<->TT color palette mapping,
but about e.g. 16/4/2 color modes.   Both TT and ST modes?

	- Eero

On 02/20/2016 04:45 PM, Roger Burrows wrote:
Hi Eero,
On 20 Feb 2016 at 11:37, Eero Tamminen wrote:

Bank number is taken into account in the ST & TT color register writes.

Looking at my previous message, I can see that I did not explain the situation
clearly enough.  If you switch banks (by writing to the TT shifter), the
display screen does not switch to the new palette corresponding to the changed
bank number.  It does on real hardware.  On Hatari, the displayed palette
remains the same as before the switch.

I have a very simple program that uses bank switching and works on my real TT
but not on Hatari.  I can post it if necessary.


On 02/19/2016 08:05 PM, Roger Burrows wrote:
When running in ST Low, ST medium, or TT medium, the TT video hardware
bankswitching for the palette: the part of the TT palette that maps to the
STe-compaitble palette can be changed, by changing the "bank number" in the

After power-on reset, the bank number is the set to zero, which causes the
first 16 TT palette registers to map to the STe palette registers.  If you
the bank number to N, then TT palette registers 16*N to 16*N+15 are mapped
instead.  There is even a special TOS3 XBIOS call, EsetBank(), to do this.

Hatari does not support this.

In video.c, function Video_TTShiftMode_WriteWord(), I think that there needs
be a check for bank number, which would then be used (I don't want to
where) to do the mapping.

Tested on a real TT, and documented in "Atari TT030 Hardware Reference


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