CDTV addressing questions

[Yulquen74]

I have been asked about making my FASTRAM board for A500(+)
CDTV friendly. Having no CDTV myself, I would need some help from the experts.

As of now, my board contains 16MB of non autoconfigured SRAM, and the SPLD logic on the board opens up the following ranges (of which some can be controlled with switches):

0x200000-0x9FFFFF (8MB Z2 RAM area)
0xA00000-0xBDFFFF
0xC00000-0xDBFFFF (autoconfigured by kickstart)
0xE00000-0xE7FFFF
0xF00000-0xF7FFFF

Theres also a small Gary board which patches address accesses
in the ranges other than the Z2 to look like accesses to 20xxxx, hence
it will generate proper non delayed #DTACK for the RAM board and side-cars,
and there will be no conflicts with the Agnus address realm.

This setup works quite well on A500(+) setups.

CDTV on the other hand, has an address map like this (if this one is correct):

000000-0FFFFF Chip memory
100000-1FFFFF Space for extra chip memory (Megachip)
200000-9FFFFF Space for AutoConfig memory
A00000-BFFFFF CIA chips
C00000-C7FFFF Space for slow-fast memory
C80000-DBFFFF Space
DC0000-DC7FFF Power backed-up real time clock
DC8000-DC87FF Non-volatile RAM
DC8800-DCFFFF Space in non-volatile RAM decoded area
DD0000-DEFFFF Space
DF0000-DFFFFF Custom chips
E00000-E7FFFF Memory card address space for front panel memory card
E80000-E8FFFF AutoConfig configuration space
E90000-E9FFFF First AutoConfig device, used by DMAC
EA0000-EFFFFF Space for other AutoConfig devices
F00000-F3FFFF CDTV ROM
F40000-F7FFFF Space in CDTV ROM decoded area
F80000-FBFFFF Space in Kickstart ROM decoded area (used by Kickstart 2) FC0000-FFFFFF Kickstart ROM

Immediately I see I would have to stop patching the 0xF00000-F7FFFF area as FASTRAM as it will block the CDTV ROM. That area would also have to be
closed on the FASTRAM-board.

Would it still be ok to have FASTRAM at 0xA00000-BDFFFF if it is patched in Gary as before although the address map claims it for CIA space?

My initial assumption is that the A500 CIA space that starts at 0xBFD000 is still used, only it is mirrored downwards.

Other than that please comment on other possible memory conflicts I should be aware of.

Thanks in advance for any help.

[Toni Wilen]

Originally Posted by Yulquen74

Immediately I see I would have to stop patching the 0xF00000-F7FFFF area as FASTRAM as it will block the CDTV ROM. That area would also have to be
closed on the FASTRAM-board.

Yes. F40000-F7FFFF is unused. (But do not put ram there, it can be used as an extra ROM space with simple hardware modification)

Would it still be ok to have FASTRAM at 0xA00000-BDFFFF if it is patched in Gary as before although the address map claims it for CIA space?

Yes. That space is unused (Possibly some protections or buggy programs access it and assume CIA). Gary CIA address space decoding was really simple, "fixed" in Gayle.

Other than that please comment on other possible memory conflicts I should be aware of.

CDTV ROM checks for memory card ram expansion at 0xe0xxxx. (It is linear mapped). If you have RAM there, it will be detected as memory card RAM. It must not be added to system ram list.