|A1200 to A4000 CPU slot adapter. just a few related questions / thoughts. not worth it's own thread.|
so someone mooted the idea of an A4000 to A1200 CPU slot adapter. now i'd love to stick a Vamp in my A4k - but i have a few stumbling blocks.
on the V1200 card, are the Address lines A24 to A31 implemented to the slot connector, or is it a 24bit address design? as only those lines are connected on the actual A1200 mainboard anyway?
now the A1200 CPU slot looks to be MOSTLY there. but we're missing:-
_BGACK - bus grant acknowledge
_CBACK - cache burst acknowledge
_CBREQ - cache burst request
_CIIN - cache inhibit in
_ClOUT - cache inhibit out
_ECS - early cycle start
_IPEND - interrupt pending
_OCS - operand cycle start
_STERM - synchronous termination
A(31:24) - top 8 address lines
also i need to look at what address range the V1200 sticks its 128meg ram.
so this could lead to a range of possibilities not limited to:-
1. the A4000 doesn't start at all
2. the A4000 does start, but only with all motherboard fast ram removed and NO Zorro cards detectable
3. the A4000 starts, no mainboard fast ram, but Zorro2 capability is available.
4. the A4000 starts, the V1200 cpu card's ram is mapped to the A4000's cpu slot ram address range so mainboard fast ram capability is available, and Zorro cards are available - but again, only in Zorro2 mode (those pesky address lines)
i can't see Zorro3 capability being available without full bus protocol signals being available, and the full 32bits of addressing. we can probably lose the cache control lines, but i'm not so sure OCS/ECS and BGACK are so easily ignorable?
now i know that there is an A4K CPU board to A1200 Slot adapter - in the shape of the micronic Mk3Z3-PCI busboard thing. and that was only able to have "slower" Zorro3 available when an A4K CPU card was installed - which kinda bears out my thoughts that the A4000 CPU cards expect and provide a lot more bus control logic.
also, if it was easy enough for someone like me to do, surely someone would have done it by now! ;)
but i'm a total novice - so any guidance or advice is most welcome. :)