6502

141 Articles

DIY GameTank Game Console Gets Upgraded Cartridge

January 5, 2023 by 2 Comments

Over the summer, you might recall seeing a homebrew 6502 game console called the GameTank grace these pages. The product of [Clyde Shaffer], the system was impressively complete, very well documented, and even had a budding library of games.

Recently, [Clyde] took to the r/electronics subreddit to show off the latest improvement to the GameTank: a revised removable cartridge. The biggest change this time around is the addition of 32 KB of battery-backed SRAM that gives games (or any other software that might be on the cartridge) some persistent storage to work with. Continue reading “DIY GameTank Game Console Gets Upgraded Cartridge” →

Squeezing A Minimalist 6502 Retrocomputer Onto A Single Breadboard

January 4, 2023 by 10 Comments

Over the years, and especially lately, we’ve seen tons of single-board retrocomputer builds. That’s fine with us — the more, the merrier. But they all start to run together a bit, with little to distinguish between them. Not so this about-as-compact-as-possible 6502 computer that fits on a single breadboard.

Now, when you do the math, it seems like there’s no way that [Anders Nielsen] would have been able to fit even a minimal chipset onto a standard solderless breadboard. The 40-pin 6502 alone takes up nearly two-thirds of the connections available; add in equally large but necessary chips like the 6522 interface adapter, ROM and RAM chips, and some support ICs, and one breadboard isn’t going to cut it. Luckily, some frugal engineers at MOS back in the 70s came up with the 6507, a variant on the 6502 in a 28-pin DIP. The other key to this build is the 6532 RAM-I/O-timer chip or RIOT, which puts a tiny amount of RAM and some IO lines on a single 40-pin DIP. Along with a 28-pin ROM, a 14-pin hex inverter, and a little crystal oscillator, the entire chipset just barely fits on a single breadboard.

But what can this minimalist 6502 actually do? As you can see in the video below, anything a 555 timer can do, and maybe a little bit more. That’s not a dig, of course — [Anders] actually calls out his initial blinkenlight application as a little more than a glorified 555, and actually comes up with a marginally more complex application just to prove the point. The interesting part here is dealing with the constraints imposed by the limited resources available on this machine.

We’re looking forward to whatever comes next for this clever build. It’s hard to see how some of the plans [Anders] has for it will still fit on a single breadboard, though — these things tend to spread out as they go.

Continue reading “Squeezing A Minimalist 6502 Retrocomputer Onto A Single Breadboard” →

Teensy Twofer Of Plug-In Emulated Retro CPUs

December 26, 2022 by 12 Comments

[Ted Fried] wrote in with not one but two (2!) new drop-in replacements for widespread old-school CPUs: the Zilog Z80 and the Intel 8088. Both of the “chips” run in cycle-accurate mode as well as in a super turbo mode, which can run so fast that you’ll need to use the Teensy’s internal RAM just to keep up.

Both of these designs have a hardware and software component. The PCBs basically adapt the pinout of the Teensy to the target CPU, with a bunch of 74VLC latches on board to do the voltage level conversion. The rest is a matter of emulating all of the instructions on the Teensy, which is more than fast enough to keep up. If this sounds familiar to you, it’s basically the same approach that [Ted] used last year to bring us his replacement for the 6502 found in the Apple ][ and Commodore 64.

Why would you want an emulated CPU when the originals are still available? [Ted] inherited a busted Osborne I, an ancient Z80 luggable. By replacing the original Z80 with his emulation, he could diagnose the entire system, which led him to discover some bad DRAM chips and get the old beast running again. Or maybe you just want to play IBM XT games at insane speeds?

And it looks like [Ted] has updated his 6502 emulation to include the undocumented C64 opcodes, so if you’re into that scene, you should be covered as well.

If any of this tickles your fancy, head over to [Ted]’s blog, microcore labs, and follow along. Although now that he’s covered most of the famous retrocomputers, we have to ask ourselves what processor is going to be next?

Blinky Project Is 6502s All The Way Down

December 24, 2022 by 19 Comments

Virtually any platform you might find yourself programming on has some simple method of running a delay. [Joey Shepard] got rather creative on a recent project, though, relying on a rather silly nesting method that we’re calling 6502s All The Way Down.

The project in question was a simple PCB that was shaped like a robot, with blinking LED eyes. Typically, you’d simply reach for the usual sleep() or delay() function to control the blink rate, but [Joey] went off-piste for this one. Instead, the PIC32 on the board runs a 6502 emulator written in MIPS assembly. This emulated 6502 is then charged with running a further 6502 emulator coded in 6502 assembly, and so on, until there’s 6502 emulators running six-deep on the humble microcontroller. The innermost emulator runs a simple program that blinks the LED eyes in a simple loop. With the overhead of running six emulators, though, the eyes only blink at a rate of roughly once every two seconds.

It’s an amusing and complicated way to write a blink program, and we applaud [Joey] for going to all that trouble. We imagine it was a great way to learn about programming the PIC32 as well as emulation in general. Meanwhile, if you’re working on your own emulator feats, be sure to let us know!

A Cassette Interface For A 6502 Breadboard Computer, Kansas City-Style

October 11, 2022 by 25 Comments

It’s been a long time since computer hobbyists stored their programs and data on cassette tapes. But because floppy drives were expensive peripherals and hard drives were still a long way from being the commodity they are today, cassettes enjoyed a long run at the top of the bulk data storage heap.

Celebrating that success by exploring the technology of cassette data storage is the idea behind [Greg Strike]’s Kansas City decoder project, which he hopes to use with his [Ben Eater]-style 6502 computer. The video below explains the Kansas City standard in some detail, and includes some interesting historical context we really hadn’t delved into before. There are also some good technical details on the modulation scheme KCS used, which [Greg] used to base his build. After a failed attempt to use an LM567 tone decoder chip, he stumbled upon [matseng]’s KCSViewer project, which decodes KCS-encoded audio signals using nothing but discrete components.

[Greg]’s prototype has a comparator to convert sine waves to square waves, followed by pair of monostable timers, each tuned to either the high or low frequency defined in the KCS specs. A test signal created using Audacity — is there anything it can’t do? — was successfully decoded, providing proof of concept for the project’s first phase. We’re looking forward to the rest of the series, which will turn this into an actual decoder, and presumably add an encoder as well.

Listeners of the Hackaday Podcast may recall we experimented with using KCS to hide some data within an episode a few months back.

Continue reading “A Cassette Interface For A 6502 Breadboard Computer, Kansas City-Style” →

Front and back of a handheld 6502 computer with bubble LED displays

The Pocket265 Is A Pocket-Sized 6502 Single-Board Computer

September 7, 2022 by 13 Comments

Single-board computers have been around ever since microprocessors became affordable in the 1970s and never went away. Today we have Raspberry Pis and LattePandas, while back in the ’70s and ’80s there were the Ferguson Big Board, the KIM-1 and a whole array of Intel SDK boards. Although functionally similar to their modern counterparts with a CPU, RAM, ROM and some basic peripherals, the old boards were huge compared to today’s tiny platforms and typically required a rather beefy power supply to operate.

It doesn’t have to be that way though, as [Aleksander] shows with the Pocket265: a handheld 6502 single-board computer somewhat reminiscent of the famous KIM-1. Like that classic machine, it’s got a hexadecimal keypad to enter programs using machine code and a row of LED displays to show the programs’ output. Unlike the KIM, the Pocket265 is small enough to hold in one hand and uses bubble LED displays, which make it look more like a programmable calculator from the 1970s. It comes with a lithium battery that makes it truly portable, as well as a sleek 3D printed case to make it more comfortable to hold than a bare circuit board.

The single ROM chip contains a monitor program that runs the basic user interface. It also makes programming a bit less tedious by implementing a number of system calls to handle things like user input and display output. A serial EEPROM enables local data storage, while a UART with a USB interface enables data transfer to other computers. If you’re interested in building and programming such a machine yourself, [Aleksander] helpfully provides code examples as well as full hardware documentation on his GitHub page.

The 6502 remains a firm favorite among hardware hackers: some projects we recently featured with this CPU include one beautifully made machine, this easy-to-build single-board computer and this huge breadboard-based contraption. Looking for something smaller? Try this tidy little board or this 6502 coupled to an FPGA.

Laptoppin’ Like 1975

August 6, 2022 by 22 Comments

When we first saw the PZ1 laptop — a 6502 laptop-style computer with a small display and 512K of RAM — we couldn’t help but think of the old AIM 65 computer from Rockwell, although that only had 1K of memory. The other thing the AIM didn’t have was an ancillary microcontroller to help out that is way more powerful than the main processor.

There are actually several versions of the PZ1 and you can find some very detailed information over on Hackaday.io and GitHub. Recently, [Adam] release version 2.0 and tested some PC boards that are working well.

Continue reading “Laptoppin’ Like 1975” →