Wax Over the years, I’ve looked for an Assembler for the VIC-20. Sure, there are great cross-assemblers like Kick Assembler, but I wanted something that would run on the VIC-20 itself. Is the VIC-20 a good machine on which to write assembly? Maybe not ON the machine. The 22-column screen is a bit limiting, but after spending so much time in Turbo Macro Pro on the C64, I wanted to see what I could do on the VIC-20 natively.

Over the years, I’ve been on a silly quest to do 10PRINT on as many things as I can. They end up on X, here, or sometimes both. I hadn’t considered it before because I just figured I couldn’t print the "/" and "\" characters on the HP-42s. I was wrong. It’s pretty easy. After a few minutes in the manual, I figured it out. 00 { 45-Byte Prgm } 01▸LBL "TEN" 02 RAN 03 RAN 04 X>Y?

My son, now 25, was a McNuggets fan. Can you blame him? They’re delicious. He’s always been into numbers and puzzles, so I introduced him to the McNuggets problem when he was about 10. This classic puzzle was a fun way to keep him occupied and teach him programming. The problem is simple: McDonald’s used to sell Chicken McNuggets in 6, 9, and 20 packs. What is the largest number of McNuggets you cannot buy using these package sizes?

Back to the basics with basic Let’s say for a moment that we’ve got an ordered list of numbers. 1,3,5,7,9,11,13,15,17,19,21,23,25 There are 13 values here and we want to check if the number 25 is in this list. One way to do this would be to loop over each element in the list and check to see if it matches what we’re looking for. In BASIC, we’d do something like

I’ve done a lot of silly math, ciphers and asked a lot of my vintage hardware on this site over the years. But I’ve not talked a ton about optimizing code for faster results. Today, we will count from 0 to 2^24-1 (16,777,215). Nothing else. Count, time it, and see how fast we can get it to go. Rust In Rust on my 2020 MacBook Pro: use std::time::{Instant}; fn main() { // Start timing let start = Instant::now(); // Loop from 0 to 16777215 for _i in 0.

Recently, we looked at a simple LFSR and how it works. Shift the bits XOR some of the bits together; we call these the taps Replace a bit with the XORed value. Repeat Easy peasy. I’ve long been fascinated by the Sound Interface Device (SID) in the Commodore 64, mostly because you can use it to get random numbers. But how does it work? The Commodore 64 SID LFSR is 23-bits.

What is an LFSR? An LFSR is a Linear Feedback Shift Register. It’s a simple way of generating a sequence of numbers that look random. Used in cryptography and in generating pseudo-random numbers, they are interesting because they are so simple. Shift bits and feed a few of them back into the sequence. That’s it. Important note: LFSRs are not cryptographically secure on their own. ESPECIALLY 8-bit LFSRs. More on that in the next post on this topic.

Commodore BASIC 2.0 A lot of fun with binary numbers can be had by printing them to the screen. This is a quick post to show how to do that with Commodore BASIC 2.0. This is a follow up to Quick Post: XOR in Commodore BASIC 2.0. We’ll be using both of these in upcoming posts, so it’s good to have them handy. 5 REM PRINT ALL 8 BIT NUMBERS IN BINARY 10 FOR N= 0 TO 255 20 FORI=7 TO 0 STEP-1 25 B=0 30 IF N AND 2^I THEN B=1 40 PRINTMID$(STR$(B),2); 50 NEXT 60 PRINTN 70 NEXT This prints all the numbers from 0 to 255 in binary.

The “famous” 10PRINT program on vintage computers was a delight for many in the 70s and 80s. It’s fun to port to other platforms and machines. I’m always looking for calculators that can do it. It requires both a slash - ASCII character 47, and a backslash - ASCII character 92. Most calculators can print the forward slash, but the backslash is only sometimes implemented. No one is surprised; calculators have limited space, and printing random patterns isn’t a primary function for standard use cases.

I was recently on a video call with a friend, throwing around some ideas for a new product. I mentioned adding large signed numbers in assembly and using two’s complement. He asked me what two’s complement was. I was a little surprised that he didn’t know. He’s been a Java programmer for more than 30 years. Java and Python programmers (and others like gasp Commodore / MicroSoft BASIC) don’t have a native unsigned integer type.

N-Queens Problem The N-Queens problem is a classic in computer science. Place N queens on an NxN chessboard such that no queen can attack another queen. Wut. Imagine you’ve got a chessboard and a bunch of queen pieces. Your mission is to place these queens on the board so that none of them can attack each other. That means no two queens can be in the same row, column, or diagonal.

I have a BUNCH of nieces and nephews. Over the years, doing some secret message passing with them around birthdays and holidays has been fun. The “secret” location of hidden Christmas presents is a favorite. Traditionally, we’ve used a transposition cipher like the Shift or Ceasar Cipher For something different, we’re going to use another transposition cipher called the Rail Fence Cipher. It is easy to implement and understand. Plus easy to break, so it’s a good teaching tool.

Rockwell International was a powerhouse of the 1970s and 80s. The Rockwell AIM 65 computer, also known as the Advanced Interactive Microcomputer 65, is an early microcomputer produced by Rockwell International in the late 1970s. It was essentially a development system, intended primarily for engineers, educators, and hobbyists, and was named for its built-in alphanumeric keyboard and LED display. The AIM 65 was built around the 6502 microprocessor, the same chip used in popular systems like the Apple II, Commodore PET, and Atari 2600.

Modern and retro mix One of my favorite peices of retro clone hardware is Bob Corsham’s KIM-1 Clone. I’ve featured it many places like the 6502 speed series. I have the latest model of this board, and he made an interesting design choice. It actually has an FTDI chip on board and you use that via USB to connect via a modern computer with an FTDI driver. This is very convenient for working with a modern computer, but then eliminates the ability to use a real serial port.

In the world of tech, including vintage tech, the lure of the blinkenlight is strong. And if you don’t like blinkenlights, can we even be friends? My PiDP-8 might be the ultimate in blinkenlight flexing, BUT we can probably do some other fun stuff if we use math. And science! Vicarious excitement is not as good as the real thing, he finds. - Cryptonomicon Neal Stephenson, 1999 Let’s make some 8 bit computer equipment output some stuff “in the real world” shall we?

My friend Robin’s favorite demo is 10 print. And what’s not to love about 10 print? After all, there’s even a book about it. My Favorite Demo My favorite demo is more complex but still simple enough to understand. The Maze Generator, from Compute! December 1981 by Charles Bond has been a favorite of mine since it came out. In the filing cabinet of my mind, I even remember it as the “Page 54 Maze”.

Have you ever sat down at your old Olympia typewriter and felt compelled to write poetry in which each word is the same length as successive digits of Pi? Me too!!! This is called a Pilish: The idea of writing a sentence (or longer piece of poetry or prose) in which the lengths of successive words represent the digits of the number π (=3.14159265358979…) has been around since the early 1900’s.

I’ve participated in National Novel Writing Month for the last two years. While I don’t have aspirations of being a fiction author, I think there is a ton of value in writing 1500 words daily. Good writing or bad, 45000 words in a month is worth the effort. In 2021, I used a DOS 386 with Wordperfect 6.22 to complete the writing for the month and produced a pretty terrible Techno/Wilderness thriller that no one should be subjected to reading.

I built the world’s worst paper tape reader some weeks ago. It works pretty okay on anything with a USR-style port like a KIM-1 clone or a VIC-20. It at least attempts to live up to the world’s worst name. Paper tape was (and is) an interesting medium. Sure it’s hard to work with and fragile, but it also has the advantage of being slow. I mean, what’s not to like?

Dealing with large numbers in computing has been an attractive problem area for a long time. Using an average calculator might lead you to believe that it’s too tricky for most applications. But it’s not that difficult. And to prove it, we’re going to implement this calculation on machines with 8 Bit registers (I mean, cmon, on this site, you can’t even pretend to be shocked). Big numbers with the wheat and chessboard problem A classic math exercise is called the wheat and chessboard problem.

There’s a wonderful yearly online event called Advent Of Code (#adventofcode). Each day there are two code challenges that follow a holiday narrative. Some of them are easy, and some of them are quite difficult. This year I’ve attempted to do as much of it as I can on 8-Bit Machines. Mostly Commodore 64 because it’s what I know the best, and also what I like most to actually code on.

I’m a Commodore guy through and through. This isn’t tribalism, it’s what was in my room from 1983 to when I graduated High School in 1993. After my sorta failed attempt at spending the month of September with my Coco 2, I decided for October to try spending a week at a time with a particularly less familiar computer. So starting on October 1st, and ending on the 7th, I spent my free time with the Atari Systems that I have.

One of my main goals in sharing retro computing is to help people DO things with these machines. They are useful for all sorts of reasons, not the least of which is education and demonstration. The constraints are wonderful for this. Using 30-50 year old hardware comes at a price. They are, well… old. They require constant care and maintenance and parts are becoming more and more scarce. Enter the retro pinout project In fixing or maintaining these old computers, one of the best resources you can have is a similar working model next to it.

An “almost teenager”, Josh, sent me an email yesterday asking how I do slow text on the Commodore. He is just starting assembly at 12 which is pretty impressive. He’s been using KickAssembler, but wants to try it “on hardware”. It’s not difficult really. There are probably a lot of ways to do this, here’s how I do it in Turbo Macro Pro. Let’s start with some text: ARE YOU KEEPING UP?

Some time in the month of September 2020 I dug out the old Commodore 64 that my Dad bought for himself in 1983. It quickly migrated its way into my room and stayed there until 1993 when I joined the Navy. Someone in my family, probably Mom, carefully packed it back into its original box and put it into storage. Despite its many years of use/ abuse by a messy teenager, it’s in surprisingly good condition, 38 years later.

People are funny on the internet. We always seem to divide into tribes even when it’s not necessary or advantageous to do so. I wasn’t surprised to see someone (there’s always one isn’t there?) comment that I might be using real hardware, but for only part of my retro setups. “I’m disappointed that you’re using an LCD monitor on your retro computers” You’re… disappointed? Kinda dramatic isn’t it? Do I get more pleasure out of doing retro on real hardware rather than emulators?

It was just a few months ago that I started to get back into 8-Bit computing. It started with Ben Eater’s Breadboard 6502 build. Something about his complete exploration of that build including single stepping the clock and watching the processor registers was really compelling to me. I built Ben’s project by following along with the videos. It’s currently inside a shadowbox in my office wall blinking away :-) My wife was the only one not surprised that two months later I was completely immersed in the “modern” 8-Bit computing scene.