A Dis-Integrated 6502

The 6502 is the classic CPU. This chip is found in the original Apple, Apple II, PET, Commodore 64, BBC Micro, Atari 2600, and 800, the original Nintendo Entertainment System, Tamagotchis, and Bender Bending Rodriguez. This was the chip that started the microcomputer revolution, and holds a special place in the heart of every nerd and technophile. The 6502 is also possibly the most studied processor, with die shots of polysilicon and metal found in VLSI textbooks and numerous simulators available online.

The only thing we haven’t seen, until now, is a version of the 6502 built out of discrete transistors. That’s what [Eric Schlaepfer] has been working on over the past year. It’s huge – 12 inches by 15 inches – has over four thousand individual components, and so far, this thing works. It’s not completely tested, but the preliminary results look good.

The MOnSter 6502 began as a thought experiment between [Eric] and [Windell Oskay], the guy behind Evil Mad Scientist and creator of the discrete 555 and dis-integrated 741 kits. After realizing that a few thousand transistors could fit on a single panel, [Eric] grabbed the netlist of the 6502 from Visual6502.org. With the help of several scripts, and placing 4,304 components into a board design, the 6502 was made dis-integrated. If you’re building a CPU made out of discrete components, it only makes sense to add a bunch of LEDs, so [Eric] threw a few of these on the data and address lines.

This is the NMOS version of the 6502, not the later, improved CMOS version. As such, this version of the 6502 doesn’t have all the instructions some programs would expect. The NMOS version is slower, more prone to noise, and is not a static CPU.

So far, the CPU is not completely tested and [eric] doesn’t expect it to run faster than a few hundred kilohertz, anyway. That means this gigantic CPU can’t be dropped into an Apple II or commodore; these computers need a CPU to run at a specific speed. It will, however, work in a custom development board.

Will the gigantic 6502 ever be for sale? That’s undetermined, but given the interest this project will receive it’s a foregone conclusion.

Correction: [Eric] designed the 555 and 741 kits

Hackaday Links: January 24, 2016

The RepRap wiki was spammed this week. Everything is fine now, but I feel I should call attention to the fact that the RepRap wiki needs some people to contribute, organize, and maintain everything. The wikis for obscure anime shows are better than the RepRap wiki, so if you’re looking to contribute to an important open source project, there ‘ya go.

The 200cc, 5.5HP, 4-stroke OHV Honda GX200 engine is found in a whole lot of tools, and is a fantastic power plant to build a go-kart around. It also costs about $350. There are clones of this engine available direct from China for about $100. Here’s how you add a turbo to one of these clone engines.

Freescale makes some pretty cool sensors and [Juan Ignacio Cerrudo] figured they needed breakout boards. He has some boards for a low-power three-axis accelerometer, an accelerometer and magnetometer, and a pressure sensor.

The Tektronix TDS744A is an older but still extremely capable 500MHz, 2Gsps, 4-channel scope. You can upgrade it to the 1GHz TDS784A by desoldering a few resistors. Very cool if you’re looking for a cheap-ish 1GHz scope.

[TheBackyardScientist] hung out with some cub scouts a few weekends ago and launched a high altitude balloon over Florida. The payload included a game camera, APRS tracker, GoPro, and a few other bits and bobs. The balloon reached 106,000 feet and landed only a few miles from Cape Canaveral.

Big RC planes – UAVs especially – are a pain to launch. Flying wings above a certain size are just dangerous to launch by hand, and landing gear is heavy and for the most part unnecessary. What’s the next best solution? A trebuchet, of course. It mounts on a car and is able to give a UAV a little bit of altitude and some speed. A pretty good idea that could be easily implemented with some load-bearing PVC pipe.

Everybody likes the Game of Life, so here’s one built with a 6502. It’s built around a Western Design Center 65c816 board we’ve seen before, nine MAX7219 LED controllers mapped to the VIA, and nine 8×8 LED matrix displays. Here’s a video of it in action.

About a month ago, a search of AliExpress turned up Apple’s A8 CPU. I bought one. Here’s what I got. It’s a stupidly small pitch BGA, and I don’t have a datasheet. What am I going to do with it? Make a non-functioning board with a few ports, resistors, no traces, and the A8 chip planted square in the middle.

A Teensy Logic Analyzer For A 6502

[John] has an interesting, if old piece of tech sitting on his workbench. It’s an Ohio Scientific C3-8P computer from the late 70s by way of a few garages, basements, and attics. As with most tech of this vintage, there are some problems, and [John] found debugging a little frustrating without the ability to trace and watch the programs. He needed a logic analyzer, and found one in an unlikely piece of hardware. [John] built one using a Teensy microcontroller, and further refinement of this project could turn it into a full in-system emulator.

The old Ohio Scientific computer [John] is trying to bring back from the dead is based on the 6502 CPU. That’s sixteen address lines to monitor, eight data lines, and four control lines. These were wired directly to a Teensy 3.1.

Reading and controlling all the signals from a 6502 is a task that falls to Linux. A command line program controls the Teensy and is capable of reading memory, setting trigger addresses, dumping the entire address space to a file, or just recording the last 5,000 clock cycles. This kind of tech existed back in the late 70s and early 80s. It also cost a fortune. Now, with a $20 Teensy and probably another $30 in ribbon cables and test clips, anyone can build a logic analyser for a very old computer system.

Videos below.

Continue reading “A Teensy Logic Analyzer For A 6502”

Upgrade Your Computer the 1985 Way

Today when you want to upgrade your computer you slap in a card, back in the early 80’s things were not always as simple.  When [Carsten] was digging around the house he found his old, and heavily modified Rockwell AIM 65 single board computer, flipped the switch and the primitive 6502 machine popped to life.

Added to the computer was a pile of wires and PCB’s in order to expand the RAM, the I/O to form a “crate bus” and of course tons of LED blinkenlights! On that bus a few cards were installed, including a decoder board to handle all the slots, a monitor controller, a massive GPIO card, and even a universal EEPROM programmer.

If that was not enough there was even a OS upgrade from the standard issue BASIC, to a dual-boot BASIC and FORTH. Though again unlike today where upgrading your OS requires a button click and a reboot, making all these upgrades are planned out on paper, which were scanned for any retro computer buff to pour through.

[Carsten] posted a video of this computer loading the CRT initilization program from a cassette. You can watch, but shouldn’t listen to that video here.

Vulcan 74: A Masterpiece of Retro Engineering

[Radical Brad] has played around with FPGAs, video signals, and already has a few astonishing projects of bitbanged VGA on his resume. Now he’s gone insane. He’s documenting a build over on the 6502.org forums of a computer with Amiga-quality graphics built out of nothing but a 65C02, a few SRAM chips, and a whole pile of logic chips.

The design goals for this project are to build a video game system with circa 1980 parts and graphics a decade ahead of its time. The video output is VGA, with 400×300 resolution, in glorious eight-bit color. The only chips in this project more complex than a shift register are a single 65c02 and a few (modern) 15ns SRAMs. it’s not a build that would have been possible in the early 80s, but the only thing preventing that would be the slow RAM chips of the era.

So far, [Radical] has built a GPU entirely out of 74-series logic that reads a portion of RAM and translates that to XY positions, colors, pixels, and VGA signals. There’s support for alpha channels and multiple sprites. The plan is to add sound hardware with support for four independent digital channels and 1 Megabyte of sample memory. It’s an amazingly ambitious project, and becomes even more impressive when you realize he’s doing all of this on solderless breadboards.

[Brad] will keep updating the thread on 6502.org until he’s done or dies trying. So far, it’s looking promising. He already has a bunch of Boing balls bouncing around a display. You can check out a video of that below.

Continue reading “Vulcan 74: A Masterpiece of Retro Engineering”

Review: Single Board 65C02 and 65C816 Computers

The 6502 is a classic piece of computing history. Versions of this CPU were found in everything from the Apple ][, to the Nintendo Entertainment System, and the Commodore 64. The history of the 6502 doesn’t end with video games; for the last forty years, this CPU has found its way into industrial equipment, medical devices, and everything else that doesn’t need to be redesigned every two years. Combine the longevity of the 6502 with the fact an entire generation of developers first cut their teeth on 6502 assembly, and you have the makings of a classic microprocessor that will, I’m sure, still be relevant in another forty years.

The cathedral of The 6502 is Western Design Center. For more than 35 years, WDC has been the home of 6502-related designs. Recently, WDC has been interested in the educational aspects of the 6502, with one of the VPs, [David Cramer], lending his time to an after-school club teaching opcodes.

The folks at WDC recently contacted me to see if I would give their hardware a close look, and after providing a few boards, this hardware proved to be both excellent. They’re great for educators adventurous enough to deviate from the Arduino, Processing, and Fritzing zeitgeist, and for anyone who wants to dip their toes into the world of 65xx development.

Continue reading “Review: Single Board 65C02 and 65C816 Computers”

The Dan64: A Minimal Hardware AVR Microcomputer

[Juan] sent us his writeup of a microcomputer he built using an Arduino UNO (AVR ATmega328p) and some off-board SRAM. This one’s truly minimalistic.

Have a look at the schematics (PDF). There’s an Arduino, the SPI SRAM, some transistors for TV video output, and a PS/2 connector for the keyboard. That’s it, really. It’s easily built on a breadboard in a few minutes if you have the parts on hand. Flash the Dan64 operating system and virtual machine into the AVR and you’re good to go.

Now we’ve seen a few 6502-based retro computers around here lately that use a 6502 paired with a microcontroller for the interfacing, but they’ve all been bulky three-chip affairs. [Juan] wins the minimalism prize by using a 6502 virtual machine implemented in the AVR to reduce the parts count down to two chips for the whole shooting match.

Using a 6502 virtual machine was a crucial choice in the design, because there are 6502 cross compilers that will let you compile and debug code for the microcomputer on your macrocomputer and then load it into the micro to run. This makes developing for the micro less painful.

How does it load programs you ask? The old-fashioned way of course, using audio files. Although rather than using the Kansas City Standard as in days of yore, he encodes the data in short and long pulses of square waves. This might be less reliable, but it sure saves on external hardware.

Continue reading “The Dan64: A Minimal Hardware AVR Microcomputer”