There are plenty of SBC that use a native 6502. If one took an SBC with a built in breadboard one could swap around the CPU more easily and safer than experimenting on an Apple I !! I certainly would not experiment with my actual Apple 1 without seeing the results on a similar but less valuable machine. :-) bill On Tue, Feb 28, 2023 at 7:42 AM Mike Willegal via vcf-midatlantic < vcf-midatlantic@lists.vcfed.org> wrote:
Demonstrate an apple 1, configured for a 6800 but sporting a 6501 instead. It would have to run code without a rotate right instruction...
Both 6501 and 6800 has been done on clones. The WOZ monitor does not use ROR. Note that there are a couple of differences between 6800 and 6501 that require a couple of small tweaks to allow a real 6800 to work in an Apple 1. In the report I have seen with the 6501 It’s unclear if tweaks to the base design as laid out on the board are necessary. Look for Tim Colgrove’s 6501 in the New England Retro Computer Facebook group.
http://www.willegal.net/blog/?p=3968
Mike Willegal.