Re: 6510 I/O port as chip selects to expand memory

From: Michał Pleban <*lists_at_michau.name*> Date: Thu, 18 Nov 2021 13:34:45 +0100 Message-ID: <61964865.3030406_at_michau.name> · lists_at_michau.name

smf wrote:

> Be careful how you design it, the 6509 based cbm2 pretty much did what
> you're suggesting and programming them was terrible.

The 6509 had an additional functionality: the memory bank for LDA (xx),Y
and STA (xx), Y instrutions was selected separately.

Without this kind of functionality, if you just change the memory bank
with an I/O port then copying data between banks becomes practically
impossible (or at least it would require an order of magnitude more
effort) because you are always reading/writing the same bank that
contains your code.

But you are right that jumping between banks on the 6509 is a nightmare.

Regards,
Michau.