The 6502 only has 56 opcodes. The db also includes modern variants of the 6502.
I meant instructions/mnemonics.
I was referencing Simonw's post:
> Here are the 65 hardcoded opcodes
The 6502 instruction set as a database
21–30 of 31 posts
Re: The 6502 instruction set as a database
#22The 6502 only has 56 opcodes. The db also includes modern variants of the 6502.
> The 6502 only has 56 opcodes In terms of bytes that the original CPU officially recognised as instructions, it was more like ~150 (working from old memories, I may be off by one or few there). Some of the other ~106 did something unofficially, and a number were valid instructions on later versions of the design. That ~150 were grouped into 56 instructions, many with multiple addressing modes (so "load A immediate",…
> pendant
I assume you mean pedant.
Re: The 6502 instruction set as a database
#23Inspiring. I would love for the author's plan (pasted below) to get applied widely across key information sources: Instead, I hatched a plan: 1. Collect sources, and encoded the raw data in a machine-readable form 2. Study those sources, and encode my understanding as assertions, sanity-checks and validations of that data 3. Synthesise that data according to my understanding, and verify it against the sources availab…
Thanks for reposting this here.
I think I work in a similar way to this, but I've not written it down as a "manifesto" before like Simon has.
I'm going to be thinking about this as the Discovery Manifesto.... or maybe the autodidactaliser.
I've found it useful to reexpress foreign knowledge in a familiar setting. The magic is possibly that the learning seems fun because the familiar tool is fairly easy to use and the new information is expressed in the familiar way.
It's also good because it's not cheap dopamine, like looking over Youtube videos.... I watched a video on the 6502... I know how it works now??.. Youtubes do have their place, but not at the expense of doing more in depth thinking.
Re: The 6502 instruction set as a database
#24Up next: 6502 emulator in a single SQL query
:-)
Re: The 6502 instruction set as a database
#25Not sure what the advantage is, relative to the tables as CSV files.
As far as I know, most information about the 6502 instruction set comes in two forms:
- emulators/simulators/FPGA code
- books, data sheets, OCR'd PDFs of books and data sheets, text files copy/pasted from PDFs or retyped from books and data sheets
Code is likely to be heavily tested, but it makes extracting high-level information about the instruction set very difficult.
Data is easy to analyse and synthesise, but since it's described in prose there's no easy way to test or validate it - if somebody in 1984 made a typo that a particular instruction took 3 cycles instead of 2, and that error was copy/pasted and made its way into half the "6502 instruction set" websites online, how would you know? How would you detect it?
Using SQL to enforce constraints and validation gives me confidence that there aren't a bunch of typos and copy/paste errors in this data. In addition, being able to express special cases like "read-modify-write instructions applying to the accumulator do not pay the three cycle penalty" in code rather than in prose makes it more likely they will be applied correctly. Lastly, since the result is an SQL database, it can be pretty easily formatted to resemble any book or data sheet you like for simplified visual verification against book/data sheet sources.
Re: The 6502 instruction set as a database
#26Inspiring. I would love for the author's plan (pasted below) to get applied widely across key information sources: Instead, I hatched a plan: 1. Collect sources, and encoded the raw data in a machine-readable form 2. Study those sources, and encode my understanding as assertions, sanity-checks and validations of that data 3. Synthesise that data according to my understanding, and verify it against the sources availab…
The last step should be: 4. Get a real 6502 CPU and verify that the data is correct.
Re: The 6502 instruction set as a database
#27Something I realized years ago, the 6502 instruction set is small enough that it can be (almost) entirely implemented as memory look up — no actual logic computation need occur.
if you allow multiple sequential memory lookups, this is true for any instruction set
Re: The 6502 instruction set as a database
#28Since this is SQLite SQL, I copied it into a Gist (to give it CORS headers) and now you can open it directly in Datasette Lite (Datasette in WebAssembly running entirely in the browser): https://lite.datasette.io/?sql=https://gist.github.com/simon... Here are the 65 hardcoded opcodes: https://lite.datasette.io/?sql=https://gist.github.com/simon... And the 64 instructions: https://lite.datasette.io/?sql=https://gist.g…
I love your tool. If you want a slightly more structured version of Gists that speaks parquet try my own tool, csvbase :). I pasted this data in as https://csvbase.com/calpaterson/opcodes-6502 and you can get parquet by adding .parquet to that (https://csvbase.com/calpaterson/opcodes-6502.parquet)
Here's datasette lite running off that file:
https://lite.datasette.io/?parquet=https%3A%2F%2Fcsvbase.com...
Really nice when webby stuff works together
Re: The 6502 instruction set as a database
#29Earlier quoted context omitted.
> The 6502 only has 56 opcodes In terms of bytes that the original CPU officially recognised as instructions, it was more like ~150 (working from old memories, I may be off by one or few there). Some of the other ~106 did something unofficially, and a number were valid instructions on later versions of the design. That ~150 were grouped into 56 instructions, many with multiple addressing modes (so "load A immediate",…
The original 6502 had exactly 151 opcodes, the same as the number of pokémon in the original Pokémon games.
This is a wonderful useless fact. Thanks!
Re: The 6502 instruction set as a database
#30Earlier quoted context omitted.
> The 6502 only has 56 opcodes In terms of bytes that the original CPU officially recognised as instructions, it was more like ~150 (working from old memories, I may be off by one or few there). Some of the other ~106 did something unofficially, and a number were valid instructions on later versions of the design. That ~150 were grouped into 56 instructions, many with multiple addressing modes (so "load A immediate",…
> pendant I assume you mean pedant.
Auto-carrot strikes again…
I really must stop writing things on the phone. I'm bad enough with a decent keyboard, sometimes I make sense at all via phone input.