6502

145 Articles

Building A Reproduction Apple I

November 14, 2024 by No comments

If you think of Apple today, you probably think of an iPhone or a Mac. But the original Apple I was a simple PC board and required a little effort to start up a working system. [Artem] has an Apple I reproduction PCB, and decided to build it on camera so we could watch.

For the Apple I, the user supplied a keyboard and some transformers, so [Artem] had to search for suitable components. He wisely checks the PCB to make sure there are no shorts in the traces. From there, you can watch him build the machine, but be warned: even with speed ups and editing, the video is over an hour long.

If you want to jump to the mostly working device, try around the 57-minute mark. The machine has a basic ROM monitor and, of course, needs a monitor. There was a small problem with memory, but he eventually worked it out by inhibiting some extra RAM on the board. Troubleshooting is half of the battle getting something like this.

Want to look inside the clock generator chip? Or skip the PCB and just use an FPGA.

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Using AI To Help With Assembly

November 7, 2024 by 30 Comments

Although generative AI and large language models have been pushed as direct replacements for certain kinds of workers, plenty of businesses actually doing this have found that using this new technology can cause more problems than it solves when it is given free reign over tasks. While this might not be true indefinitely, the real use case for these tools right now is as a kind of assistant to certain kinds of work. For this they can be incredibly powerful as [Ricardo] demonstrates here, using Amazon Q to help with game development on the Commodore 64.

The first step here was to generate code that would show a sprite moving across the screen. The AI first generated code in all caps, as was the style at the time of the C64, but in [Ricardo]’s development environment this caused some major problems, so the code was converted to lowercase. A more impressive conversion was done in the next steps, as the program needed to take advantage of the optimizations found in the Assembly language. With the code converted to 6502 Assembly that can run on the virtual Commodore, [Ricardo] was eventually able to show four sprites moving across the screen after several iterations with the AI, as well as change the style of the sprites to arbitrary designs.

Although the post is a bit over-optimistic on Amazon Q as a tool specifically for developers, it might have some benefits over other generative AIs especially if it’s capable at the chore of programming in Assembly language. We’d love to hear anyone with real-world experience with this and whether it is truly worth the extra cost over something like Copilot or GPT 4. For any of these generative AI models, though, it’s probably worth trying them out while they’re in their early stages. Keep in mind that there’s a lot more than programming that can be done with some of them as well.

2024 Tiny Games Contest: A Flappy Seagull Game With Sound In Only 500 Bytes

September 12, 2024 by 4 Comments

It was probably a reasonable assumption that the “Tiny” in our recently concluded Tiny Games Contest mostly referred to the physical footprint of the game. And indeed, that’s the way most of the entries broke, which resulted in some pretty amazing efforts. [Anders Nielsen], however, took the challenge another way and managed to stuff a seagull-centric side-scroller into just 500 bytes of code.

That’s not to say that the size of [Anders]’s game is physically huge either. Flappy Larus, as he calls his game, runs on his popular 65uino platform, a 6502 microcontroller in the familiar Arduino Uno form factor. So it’s pretty small to begin with, and doesn’t even need any additional components other than the tiny OLED screen which has become more or less standard for the 65uino at this point. The only real add-on is a piezo speaker module, which when hooked up to the I2C data line happens to make reasonable approximations of a squawking seagull, all without adding a single byte of code. Check out a little game play in the video below.

Flappy Larus may be pretty simplistic, but as we recall, the game it’s based on was similarly minimalist and still managed to get people hooked. The 2024 Tiny Games contest is closed now, but if you’ve got an idea for a tiny game, we’d still love to feature it. Hit the tip line and we’ll take a look! Continue reading “2024 Tiny Games Contest: A Flappy Seagull Game With Sound In Only 500 Bytes” →

Single-Stepping The 6502 Processor

July 18, 2024 by 19 Comments

Although marketing folk and laypeople may credit [Steve Jobs] as the man behind the success of Apple, those in the tech world know the real truth that without [Steve Wozniak] nothing would have ever gotten off the ground during the early days of the computer company. As an exhibit of his deep knowledge of the machines he was building, take a look at this recreation of a circuit by [Anders] which allows the 6502 processor to step through instructions one at a time, originally designed by [Woz] himself, even though there are still myths floating around the Internet that this type of circuit can’t work.

Like a lot of Internet myths, though, there’s a kernel of truth at the middle. The original 6502 from the mid-70s had dynamic registers, meaning they would lose their values if the chip was run below a critical clock speed. Since single-stepping the processor is much lower than this speed, it seems logical that this might corrupt the data in the registers. But if the clock is maintained to the registers the processor can be halted after each instruction, allowing even the original 6502 to go through its instructions one at a time.

[Anders]’s project sets up this circuit originally laid out by [Steve Wozniak] but updates it a bit for the modern times. Since the technology of the era would have been TTL, modern CMOS logic requires pull-up resistors to keep any inputs from floating. The key design of the original circuit is a set of flip-flops which latch the information on the data bus, and a switch that can be pressed to let the processor grab its next instruction, as well as a set of LEDs that allow the user to see the value on the data bus directly.

Of course, a computer processor of this era would be at a major handicap without a way to debug code that it was running, so there are even dedicated pins that allow this functionality to occur. Perhaps the Internet myth is a bit overblown for that reason alone, but [Anders] is no stranger to the 6502 and has developed many other projects that demonstrate his mastery of the platform.

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The ROM programmer on display, with an OLED screen attached

Relatively Universal ROM Programmer Makes Retro Tech Hacking Accessible

April 20, 2024 by 27 Comments

There’s treasures hidden in old technology, and you deserve to be able to revive it. Whether it’s old personal computer platforms, vending machines, robot arms, or educational kits based on retro platforms, you will need to work with parallel EEPROM chips at some point. [Anders Nielsen] was about to do just that, when he found out that a TL866, a commonly used programmer kit for such ROMs, would cost entire $70 – significantly raising the budget of any parallel ROM-involving hacking. After months of work, he is happy to bring us a project – the Relatively Universal ROM Programmer, an open-source parallel ROM programmer board that you can easily assemble or buy.

Designed in the Arduino shield format, there’s a lot of care and love put into making this board as universal as reasonably possible, so that it fits any of the old flash chips you might want to flash – whether it’s an old UV-erasable ROM that wants a voltage up to 30 V to be written, or the newer 5 V-friendly chips. You can use ICs with pin count from 24 to 32 pins, it’s straightforward to use a ZIF socket with this board, there’s LED indication and silkscreen markings so that you can see and tweak the programming process, and it’s masterfully optimized for automated assembly.

You can breadboard this programmer platform as we’ve previously covered, you can assemble our own boards using the open-source files, and if you don’t want to do either, you can buy the assembled boards from [Anders Nielsen] too! The software is currently work in progress, since that’s part of the secret sauce that makes the $70 programmers tick. You do need to adjust the programming voltage manually, but that can be later improved with a small hardware fix. In total, if you just want to program a few ROM chips, this board saves you a fair bit of money.

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A Low-Cost ROM Programmer With An AI Twist

March 23, 2024 by 11 Comments

There are 0x10 ways to look at ROM programmers: they’re either relatively low-cost tools that let you quickly get about the business of programming vintage ROMs and get back to your retrocomputing activities, or they’re egregiously overpriced on a per-use basis. [Anders Nielsen] seems to land in the latter camp, firmly enough that he not only designed a dedicated ROM programmer for his 65uino ecosystem, but also suffered the indignities of enlisting ChatGPT to “help” him program the thing.

We’ll explain. [Anders]’ 65uino project has been going on for a while, with low-cost ROM programming only the latest effort. To his way of thinking, a $60 or $70 programmer might just be a significant barrier to those trying to break into retrocomputing, and besides, he seems to be more about the journey than the destination. He recently tackled the problem of generating the right programming voltages; here he turns his attention to putting that to work programming vintage ROMs like the W27C512.

Doing so with a 6502-based Arduino-compatible microcontroller requires some silicon calisthenics, including a trio of shift registers to do the addressing using a minimum of GPIO. As for the ChatGPT part, [Anders] thought asking the chatbot to help write some of the code would be a great way to increase his productivity. We thought so too, at least once, and like us, [Anders] concluded that while perhaps helpful in a broad sense, the amount of work you put into checking a chatbot’s work probably exceeds the work saved. But no matter, because in the end the code and the hardware came together to create a prototype ROM programmer for only about $10 worth of parts.

True, the resulting circuit is a bit complex, at least on a breadboard. It should clean up nicely for an eventual PCB version, though, one that plugs right into the 65uino board or even other microcontrollers. Either way, it could make creating custom ROMs for the 65uino a little more accessible.

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It’s A CoCo! No, It’s An Apple II!

March 2, 2024 by 2 Comments

Original retrocomputing hardware is now decades old and showing its age, so the chances are it’s more common in 2024 to experience a machine from the 1970s or 1980s by way of an emulator on a modern machine than it is on the real hardware. There’s another more limited emulation scene as similar 8-bit machines emulate each other, for example when the very similar Dragon 32 and Tandy CoCo have a go at each other’s software. Rarest of them all though is when one classic machine emulates another with a different architecture, but that’s exactly what’s happened with [DragonBytes], who has persuaded a Tandy CoCo to emulate an Apple II.

The two machines have significant hardware differences, but we’re guessing that the project is helped a little by the Motorola 6809 in the CoCo and the MOS 6502 in the Apple having both in a sense been different visions of a successor to the Motorola 6800. Thus their architectures while different, are not diametrically opposed. The other hardware is certainly not so similar though, with Moto’s 6847 display chip in the Tandy being far more conventional than Steve Wozniak’s clever NTSC hacks to achieve a color display for minimal cost on the Apple.

The project is written in assembler, and doesn’t by any means claim to support all Apple modes, or be cycle accurate. But it’s a hugely impressive achievement nevertheless.

The CoCo has an enthusiastic following, and has appeared here a few times in the past. We particularly like this video player.