When I first heard about the Replica One, I was jumping for joy. I thought that was the coolest thing ever. I bought the Building the Replica One book (first printing) with the hopes of one day building it.
I also always planned to buy the Replica One kit from Briel but couldn't justify the cost at the time. Well, a DECADE later, I decide it's finally time to buy the Replica One. Now, as luck would have it, it seems Vince has gone off the grid with regards to building/selling these kits. This is my fault for waiting so long.
Anyway, the second reason for buying that book was to learn enough to build my own 6502-based computer. So I thought...why not build a "Replica One" replica? A replica of a replica! LOL
But seriously, I am designing a 6502 computer that, I would hope, would be mostly compatible with the original Apple 1. Now, here's the deal...I have several ROM's that I would like to load on it. Some that won't fit into the 8K that Vince's design uses. In fact, my design uses 32K RAM and 32K ROM (minus a little RAM for I/O).
Now, I see a few problems with this.
1) The PIA address space for keyboard / display of $D010-D013 is in conflict of my 32K ROM.
2) The $E000-$EFFF RAM space is in conflict of my ROM based on a memory map that I read:
"RAM space available for a program in an 8K system modified to use cassette BASIC"
3) A few addresses in the $CXXX space for the cassette interface. Believe it or not, I actually want to support the cassette interface.
As you can see, my 32K ROM is just going to be out of the question if I want to maintain this address space and NOT use something like CPLD/FPGA for advanced memory decoding (I don't want to use programmable logic).
So, what are my options? I suppose I could recompile the Woz mon (for example) to use a different address for the PIA. But that would probably break a lot of legacy code.
I guess the question comes down to how much Apple 1 compatibility I want vs. how much of a general purpose 6502 computer I want.
What are your opinions?