Posted By
siz
on 2023-04-12
08:39:35
|  Re: New Project: Hannes-compatible 256k RAM Expansion
- Suppose you have switched to bank 1 to do some calculations on the data there. Now you need to switch back to the TED bank (assume P6=0) to make some data available to it: what value would you write to $FD16?
It depends. In the nineties I would probably written
lda #$03 ; assuming I want bit 6&7 to be 0
sta $fd16
But then I also would have wrote
lda #$18
sta $ff07
to switch on multicolor mode, not caring about NTSC compatiblity
Nowadays (knowing that bit 2-3 can be address too) I would write
lda $fd16
and #$f0
ora #$0f
sta $fd16
or directly
lda #$3f ; assuming I want bit 6&7 to be 0
sta $fd16
- Would you write a different value according to how much expansion memory is installed in the machine? Say 256kB, 512kB and 1 MB (suppose you have already found that out).
No. I would like to use the power up value ($ff) as the default one.
- What value to you expect to see from PRINT PEEK 64790 on a machine with a Hannes-style expansion and what value to you actually get on your 6502plus4-equipped machine? Please make a real test happy.
I had to put your number into calculator to convert it to hexadecimal. 
I expect it to be $ff (that register is documented to be a 6529 which powers up with $ff)
Let's see the test:
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