Many thanks for the interesting comments. Fortunately I had BASIC, so did not need to compile the compiler by hand - in fact I am now struggling to understand the compiler source code! I took the big-endian approach for convenience, but appreciate how a little-endian approach could be implemented ...

I was finally reunited with my notes and disks on Swift this week. I can't read the disks yet, but my notes begin with the assertion that "Swift is a threaded interpreted language", then include info on the general approach (e.g. a parameter stack and a return stack), a list of primitive commands ...

For the moment, I do not understand what you write, but once I recover what I did, I will let you know.

Thank you for your interest. I think I knew more about FORTH in the 1980s than I do now (!) - DeGrandis-Harrison was almost certainly an inspiration at the time. However, I wanted to use the compilation step (from source into byte code) to make SWIFT programs more like other languages, so that the ...

I wonder if anyone here might be interested in a FORTH-like language that I wrote for the BBC Micro as a teenager in the 1980s. I called it "SWIFT" because it was faster than any other language available for the BBC Micro at that time (as measured by the Ackermann function test, which was popular ...

@joelnoche Yes, just to confirm that the hexagons simply denote flip-flops and have no other meaning. Thank you for your interest in my circuit diagram, but please note that I made this diagram primarily to understand the 6502, and made several changes to the original circuit, so it is probable that ...

Awesome - thank you so much for all your work on the 6502 - it helped me a lot in making my own circuit diagram.

I haven't had any luck figuring out how to use web fonts or embedded fonts. I've added Courier as a back-up font for the annotation layers, but it is too big to use as a substitute font in the block diagram layers, so I've used Consolas instead, which at least works on my Windows 10 system. There ...

Thanks. I made those fixes. It looks like the font issue is not about the browser, but whether the font is installed by the OS. The font in question is Latin Modern Mono Caps. I could include the font specification in the svg or convert the text to paths, but both solutions would increase the size ...

Thanks. Note that in the screenshot, the fonts have not been rendered correctly (this is probably a browser-dependent issue). Also you can click on the black squares next to the title to get more text detail (not a great user interface at present, I admit!).

As suggested above, I have now produced a version of the circuit diagram with a block diagram overlay. In a suitable browser the overlay can be switched off (or on again) by clicking on the title. It can be found at https://davidmjc.github.io/6502/bcd.svg.
Any suggestions for other improvements ...

I found and corrected several other minor errors. In particular, despite previously understanding how the sb/A decimal adjust circuit worked, I messed it up in the circuit diagram. Similarly, despite knowing that PLA line 138 has a special treatment, I forgot to include it (this is also missing in ...

Many thanks for both the comments and the correction. One of my motivations for making the diagram freely available was in the hope that others might spot some of the many errors I undoubtedly made! I have cross-checked against the visual 6502, and believe I have now fixed the circuit. I believe ...

Thanks - I did this mostly in 2018, so it is not up to date with respect of my current understanding of the chip. For instance, I now find the "Data output register" to be something of a chimera! I did at least rename "RESB" to "BRC" (for branch carry) as I believe this circuit is more about timing ...

I have a live and let live attitude to orientations (in general!). One advantage of a freely licensed diagram is that anyone is welcome to download it, rotate it and release their preferred version under cc-by-sa! I did most of my editing of the svg with the Balazs orientation, so it was a bit of a ...