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C128/C65/MEGA65 Bank switching

  • Don't forget, that you have more than 2 Banks available in the MEGA65, because it comes with build-in memory extension ;-)

  • I know, but I already asked if the BASIC 10 really can access more than BANK 0 and BANK 1.


    Hint: Moving DATA from BANK X to BANK 0/1 with MAP DMA (Stash/Fetch/Swap) is not meant.

    That's only moving Data from extended memory to 'BASIC-Memory.


    In other words: can the cpu directly access the extended memory?


    I try explain in C128- language.

    The 4502 can access 1MB, this is equivalent to C128 with 'full' MMU capability, where MMU bankswitches parts of the 1MB into cpu's '64k viewport'. The extended memory is more like the REU, where you must fetch,stash or swap parts within the range the MMU can see (and thus make availlable to the cpu).

  • Now i got you ! I'll check back with Paul.

  • Partially it's hard to explain, coz BANK is used in 2 different meanings.

    #1: Real existing hardware 64k RAM Bank and

    #2: The BASIC command 'BANK', which in fact doesn't mean a RAM-Bank but a configuration of memory.


    In case of FRE(x) we talk about real RAM-BANKs

    But you can't use pE BANK 5 to 'switch' to the 5th real RAM-BANK.

  • Additional info:

    When I activate Bank 2 & 3 in VICE, and I try to FRE(2), FRE(3) the answer is


    ?ILLEGAL QUANTITY ERROR

  • Because Bank 2 and Bank 3 on the c65 are ROMs ? Kernelroutines, etc...

    So a FRE(2) or (3) is not logical.

  • Because Bank 2 and Bank 3 on the c65 are ROMs ? Kernelroutines, etc...

    So a FRE(2) or (3) is not logical.

    No, I said "activate RAM BANK 2 & 3 in VICE x128."

    It is just that I think BASIC (neither 7.0 nor 10.x) was designed to use more than 2 RAM BANKS, one for programm, one for variables.

    Even GW-BASIC only initializes only 64k for BASIC in MS-DOS, that's why I think that from BASIC it's not possible to access more than BANK 0 and 1.

    On the other hand we can pretend that BASIC 7.x & BASIC 10.x are superior to GW-BASIC, because our 8-bit BASICs can use twice the memory (128K)

  • I have moved the discussion here regarding the Available Memory on the c65 with the help of Bank switching

  • adtbm

    Changed the title of the thread from “C65/MEGA65 Bank switching” to “C128/C65/MEGA65 Bank switching”.