Re: [stella] A new way to bankswitch

Subject: Re: [stella] A new way to bankswitch
From: "Fred Quimby" <c9r@xxxxxxxxxxx>
Date: Wed, 9 Mar 2005 18:16:03 -0500
>I don't agree on that. Look at the timing diagram for an LDA $FFF8:
>  #  address R/W description
>        --- ------- --- ------------------------------------------
>         1    PC     R  fetch opcode, increment PC
>         2    PC     R  fetch low byte of address, increment PC
>         3    PC     R  fetch high byte of address, increment PC
>         4  address  R  read from effective address
>When the LDA $FFF8 is executed, you only have the effective adress
>on the bus for one processor cycle. So If the bankswitching hardware does
>not switch, if it sees a valid adress for one cycle, it will simply not
>at all :-)
>And the 0.1 5F Cap is good for about 3005s delay. I think I calculated that
>a while ago.
>Don't know the exact value, but it is in that range. It should switch !

I assume you mean 300 ns... But anyway, I didn't realize that it would
operate that fast with a cap.  That short of a delay should allow a switch
to complete within a single cycle, so if true, I wonder if it would work in
a 16k scheme, where we could place something like this in every bank:


Then to jump to a routine in a particular bank, just do the LDA/PHA thing,
then JMP Bank_X.  If it works, it would really reduce the complexity of
writing a 16k (or larger) game.  OK, so maybe I should wait for this to be
thoroughly tested before I get too excited.

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