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Bank switching in ZX-Basic

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wilco2009

Posts: 28

Joined: Sat Nov 24, 2012 1:23 am

Post Thu May 22, 2014 9:34 am

Bank switching in ZX-Basic

I've never programmed used bank switching, but now I'm developing a new external interface to convert a 16Kb Spectrum to a machine very close to a plus 3 machine but with 512Kb of RAM, and due to it, I'm starting to be interested of this kind of programming.

Have ZXBasic support for bank-switching?. If the aswer is yes, I have a suggestion about the possibility of support for 512Kb of RAM. The method to change the page above 128Kb is the same that the used in Pentagon, ie using bits 6 and 7 of the same port than 128Kb ($7FFD).

If it is not supported, could be very interesting to do it, because if we do it manually we can only use it for data, but not for code. The best way is to implement it natively. It is not possible to do that with a library.

The main challenge could be to use the same addresses for different functions.
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britlion

Posts: 766

Joined: Mon Apr 27, 2009 7:26 pm

Location: Slough, Berkshire, UK

Post Tue May 27, 2014 6:22 pm

Re: Bank switching in ZX-Basic

Right now there is no native support for 128K. So it requires quite a bit of fiddling with banks and putting them back before the compiled code notices in order to work 128k. Probably mostly being used as a data source copying to a low memory buffer really - like a fast disk in effect.

Real support for it in the compiler, with calls into higher memory automagically would be very nice indeed.
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wilco2009

Posts: 28

Joined: Sat Nov 24, 2012 1:23 am

Post Thu May 29, 2014 5:12 pm

Re: Bank switching in ZX-Basic

I agree, due to it my question.

Perhaps is better to move the post to the whislist forum.

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