Hello everyone!

I'm Senijs from Latvia, currently a student.
I've been interested in programming and especially computer/cpu design for 2 years now. I found a simple game for my phone that was based around logic gates and it got me really interested about how computers ACTUALLY work.
I used a simulator called Logicly to build my first adder out of logic gates. Way later I began building my first processor in a better simulator called Logisim. It took me many months, but I managed to make a working processor/cpu almost entirely out of logic gates. The CPU was a replica of Paul Malvino's SAP-1 (Simple As Possible-1), which is described in a great book called "Digital computer electronics" by Paul Malvino. I also made the snake game in 6502's assembly language at https://skilldrick.github.io/easy6502/
That's the backstory. Also, I'm completely self-taught.

Right now I want to make 6502 replica in Logisim simulator and then write a simple OS for it in it. I really want to meet some people to talk to about programming and computer design in general and I think your forum is pretty awesome and you guys could teach me a lot I really want to share projects, ask for help and maybe even do collaborations with someone. I will try to engage with your communitiy, as well as with others.

If I may ask here, I would like to know what are some of the best resources/books/sites/anything that helped you with computer design and especially 6502 design. Can you provide me with general direction, please?

Thank you for reading, I'm hoping to have a great time here with you!

Hi Senijs, and welcome. A good idea to ask for recommendations: but can I suggest a new thread in General for that request? You'll probably get several responses, and it would then be easy for future adventurers to find the thread.

Or check out Hardware section, which has several threads on this topic, specifically this one: viewtopic.php?f=4&t=3493

Thank you for your replies. I will try your suggestion, BigEd.
Arlet, the thread that you posted looks like exactly what I need. I will read up on it.
I will try to search your forum for older threads and if I don't find the answers for my questions, then I will post a new thread. I think that's how forums are supposed to work. I will also try to look around and get to know your site better.

Great! Should be a very interesting journey.

I've started a thread, over here. Let's hope!

Hello,

I'm Steve and I've been a 6502 fan ever since I learned assembly language on the Apple II+ in the very early 80's.

I am working on a software interpreter for the 6502 family (6502, 65816, etc) and I created this account in order to describe and promote my project to the community. In particular, I would like to discuss a subset of my project that I am calling the "65A24".

The 65A24 is a fictitious microprocessor based on the 6502 which extends all of the absolute and indexed addressing modes of the 6502 to a full 24 bits. Think of it as a 65816 but without memory segmentation. The A, X, and Y registers are all at least 24 bits in length and indexed instructions can access all available memory. Zero page indirect instructions such as:

LDA ($fd),Y

...are capable of accessing the full 16 meg memory through the 24 bit address at $fd, $fe, and $ff, and the Y register itself can impose another 24 bit offset on top of that. The zero page is also relocatable anywhere in memory. I have written my own assembler in C++ in order to assemble code written in this format into appropriate byte code for use with the interpreter.

I have also written a "faux machine" using Qt that emulates a fictitious late 80's/early 90's era computer with a text display, ROM, and a graphics subsystem not unlike the Apple IIgs, Amiga, or Atari ST. The purpose of this "faux machine" is to exercise the capabilities of my 6502/65816 interpreter and my 65A24 interpreter.

Anyway, that's the 2-minute introduction to what I am doing and if there is significant interest in this project here, I will post source code, involve the community, and pursue this project until a tangible product is created that other people can use. I invite anybody who is curious about this project to solicit comments and ask questions!

Thanks,

Steve

Welcome - sounds great - please do start a thread!

Oh my, I seemed to have come in the back door first through the Forth section a few days ago. Please excuse me

Just to keep it short for now I will skip a lot of early and in-between stuff and talk about my first 65xx experience.

I first started using 6502s in the form of R6511AQ chips back in the early 80's when I was considering a single-chip micro for a new POS terminal design plus there were Forth ROMs which I could hack since I already had an intro to Forth and liked what I saw. Later on I progressed to the 65816 which had just become available but then in the midst of some early designs I found out about Mitsubishi's faster and better single-chip version, the M37700, so I switched to that in the 90's using the QFP80 smd package. Anyway I still had some designs with the 65816 (and external Flash) and also allowed for 6502 chips since they were quite cheap at the time. A lot of these 65xx chips ended up in POS terminals, industrial control units, vending machines, and other interesting stuff etc. A lot of engineers at the time here in Oz were using 68HC11s because that's what they were taught on in the Universities but the 37702 was a much better chip and architecture.

By the early 2000's single-chip micros were coming out with onboard Flash and a decent amount of RAM and Mitsubishi was abandoning the M37700 range and concentrating on their new M16C architecture which supported 'C', or so they said. I did some designs with this newer chip but it was a total disaster (one address pointer etc) and so I migrated to the MSP430 range and wrote a Forth for that and used it in industrial designs and vending machines. Of course I used lots of other smaller micros too such as AVRs etc. By 2004 the Philips LPC21xx ARM chips were becoming available so I gave myself a crash course by jumping straight into a project using it. I even got this chip to generate VGA signals in color while playing back audio files. I entered my ARM design called "noPC" into the 2005 Philips ARM Design Contest and made some money from that by winning 2nd prize (I didn't use the sponsor's compilers and boards). But I am still making money from products based on that design, even now.

Not long after that ARM chips went silly IMO, in the crippled Cortex direction, optimizing the CPU for C compilers, yet once again. I gave up on new designs using ARM even though I still continue to evaluate different chips (many many chips). In 2006 the Parallax Propeller caught my attention, simply because it could generate video signals directly from the chip with little effort. I had to get some including the demo board and once I did I couldn't put it down. So I've done scores of designs with this chip over the years and now I am using the successor P2 chip which amongst many other advantages has 512kB of RAM.

I'm planning to get the P2 chip to emulate a 6502 initially and also provide virtual ACIA and VIA peripherals as well as 640x480x8 VGA. So instead of an FPGA I would use the P2 in a 100-pin TQFP pack and its 64 smart pins (like a peripheral on each pin), and its eight 32-bit cores to make a 65xx system on a chip. The P2 is designed to run at 180MHz but comfortably runs over 300MHz. I'm thinking of calling this my 65P2 project There is no commercial use for this, it is just for fun.

While I have used lots of different tiny micros such as PIC, AVR, 8051, HC08 etc I have always been on the lookout for a 6502 based tiny micro, but there are none. It seems to me that a 6502+ with bit instructions such as I used on the R6511AQ would be very useful but unlike many of the other chips, the 6502 can address memory much better. So like I have a tiny Silabs EFM8UB3 chip which is 8051 based and fast, mounted on my P2 module to provide USB serial and some other functions. But it would be much nicer if it were 6502 based.

There is so much to tell that I forget most of it but I need to get some sleep now. Good-night!
Peter Jakacki
Brisbane, Australia

Hi Peter, and welcome.

Nice engineering background, please keep us updated about your 65P2 project.

Welcome Peter, great intro. It feels to me like we need a thread all about the 7700 - I looked up some datasheets and it's terribly interesting, but I've lacked the energy to put together a post on it.

Hi Peter, when I saw the post about Tachyon in the Forth sub-forum I wondered if it was the same guy from the Parallax forum. I'm the same Martin_H who built a number of Forth/Propeller powered robots that I published in the Parallax forum.

Welcome to the 6502 board.

Hello. I'm Christian, a VFX Supervisor for films and TV, and I live and work in Cardiff, Wales.

I'm currently embarking on the long and (hopefully) enjoyable journey of building a 6502-esque computer using 74HC parts. The aim is to have a computer that has a near-as-dammit cycle accurate 6502 instruction set (minus decimal mode at the moment), and its own video adapter. Version 1 at least will be a standalone computer that I can use to teach my children how computers work (currently they're 3 1/2, so they'll probably be about 8 when the computer is complete given how little time I have to build it!).

I've been lurking here for a while, attempting to figure out how the 6502 works, and designing my implementation of this legendary processor (my first two computers back in the day were the VIC-20 and C64, so I'm very fond of it).

I'll be asking quite a few questions I'm sure. Apologies in advance if they've been asked before - I'll do my best to be original!

Hi Christian, and welcome to the forum.

We happen to have a 74AC based TTL 6502 implementation that's near-as-damnit cycle accurate, supports most of the illegal instructions, and has BCD mode.
When plugged into a VIC-20 or C64, it nicely works.

Cheers,
Dieter.

Hi Dieter,

Thanks for the welcome. I'm very well aware of the project you've linked to - in fact it was this project that got me excited about building something 6502-esque! My design is quite heavily based on it actually! I'm currently building it as an emulation using Processing (processing.org) to figure out how each instruction will work, and how the control word will shape up. It's not a trivial task

I'm slowly getting to grips with Visual 6502 and the big block diagram too. I don't have an EE background, and my first introduction to building a "chip computer" was from Ben Eater's excellent video series, however this is a different beast altogether!

Cheers, Christian