Selecting RAM, Slots, Sub-Slots and port-extender

Por Accumulator

Champion (351)

imagem de Accumulator

09-04-2023, 05:14

I am wondering if there is a solution using only I/O ports to select Slot, Sub-Slot and cartridge-extender, without using the variables addresses FCC1H - FCC8H and FFFCH - FFFFH.
Primary slots can be selected by I/O port A8H, and after selected primary and secondary, you can use Port FCH - FFH for selection which 'bank' to be used.
How to check for cartridge-extender and if result of slot reading a value by using BIOS call #0CH,
is in order of F000SSPP, Is there no option for tertiary slots?
Do we not have bits enough to read this?
Am I something missing or not understanding?

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Por snake

Expert (71)

imagem de snake

21-04-2023, 17:50

To mount slots you can use port 168.
To configure an expanded slot you can mount it on page 3 then use 65535 address.
To detect an expanded slot you can mount it on page 3, write a value to 65535 then read form the same address, if values are different the slot is expanded.