"mos6502" posts for February 2015

[BigEd]

Here's our second monthly roundup - see also our partial catalogue and our profile page. Comments welcome on this thread!

2015-02-06 We feature Michael Steil's side-by-side annotated disassemblies of the C64's ROMs - both the Kernal and Microsoft Basic - and mention several other notable dissassemblies.


2015-02-13 All about Commodore's C65 - an unreleased prototype with some interesting characteristics, instances of which come up for auction every year or so. We feature Paul Gardner-Stephen's video - he is building a related FPGA project.


2015-02-20 wumpus' novel animated visualisation of dataflow within the 6502 - xray6502. We link to some related visualisations and mention the use of visual6502 in undergraduate teaching.


2015-02-27 The 65CE02, a rare late version of the 6502 direct from Commodore, and the recent discovery that it has a bug in decimal mode: SBC doesn't quite work.


We hope you enjoyed these. We try for a mix of topics, whether the various 6502 micros from back in the day, or new projects using 6502, or feats of software relating to 6502. We're also partial to details of the chip internals.

Ed and André, posting as 'mos6502'

Edit: updating links to archive links

[BigDumbDinosaur]

BigEd wrote:

The 65CE02, a rare late version of the 6502 direct from Commodore, and the recent discovery that it has a bug in decimal mode: SBC doesn't quite work.

Thinking back to those days, it seems that once Commodore took over MOS Technology and started shipping parts with the CSG logo the bugs started to appear. There was a particularly annoying one in the 6526 involving timer B interrupts, which was well-documented in Transactor magazine by both Elizabeth Deal and Paul Bosaki. Complicating matters, the timer B bug wasn't present in all 6526s.