Z80 Single-Board Computer Looks Like It Could Have Been A Killer Product

August 20, 2022 by Dan Maloney 30 Comments

Most retrocomputer builds seem to focus on either restoring old machines or rebuilding them from scratch. Either way, the goal is to get as close as possible to the original machine, and while we certainly respect those builds, there are other ways to celebrate the computers of yesterday, as this Z80 single-board computer nicely demonstrates.

[Ivan Farafontov]’s SBC is sort of a “Z80 that never was” build, one that would almost have been possible back in the heyday of 8-bit computing, and would have made quite a splash if it had. Most of the peripheral chips are from Zilog and would have been found in many of the Z80 machines of the day, like the TRS-80 and ZX Spectrum. Where it goes off the old-school path is with the video section, which uses an Atmel CPLD chip and a dual-port RAM to drive a VGA monitor. It still looks the part, though, with a 256×192 pixel, 16-color display. The compact video section helps keep the overall footprint of this machine pretty small, at least by the standards of the old machines. The machine is barely larger than its custom keyboard, which is populated with mechanical switches and really nice-looking custom keycaps, and everything fits into a 3D-printed case.

The demo that starts at the 4:30 mark of the video below will be a nostalgia storm for a lot of readers, starting as it does with a version of Boulder Dash that [Ivan] wrote from scratch, along with the tile editor he used to create the sprites for the game. All the design files and code are available if you want to build your own, of course. We recently featured another Z80 that never was, but [Ivan]’s machine really makes a statement with its compact size and its capabilities.

Continue reading “Z80 Single-Board Computer Looks Like It Could Have Been A Killer Product” →

Chips Remembered: The Scenix/Ubicom/Parallax SX

August 17, 2022 by Al Williams 70 Comments

If you are a bibliophile, going to a used bookstore is a distinctly pleasant experience. Sure, you might discover an old book that you want to read. But at least some of the endorphin rush comes from seeing old friends. Not humans, but books you read years or even decades ago. Most often, you don’t buy the book — you probably have one stashed in a box somewhere. But it is a happy feeling to see an old friend and maybe thumb through it reading a passage or two among shelves of musty books. I wish we had something like that for chips. Outside of a few notable exceptions, chips tend to have a short life span of popularity and then give way to other chips. This is especially true of CPUs. One that I especially miss is the Scenix/Ubicom/Parallax SX chip.

I had a bookstore-like experience with this processor the other day. I produced a few products based around these chips and I have a small stash of them left. I jealously guard the hardware needed to program them “just in case.” Well, naturally, someone needed a few for some reason so I had to dig it all up. Knowing these might be some of the last of the unprogrammed SX chips in the world made me a little nostalgic.

The Story

In the late 1990s, a company called Scenix started producing a microcontroller called the SX in a few footprint sizes. So the SX18 was, for example, an 18-pin part. By 1999, they were already in full swing with the SX18 and SX28 and they introduced the SX52.

Of course, a lot of companies produced microcontrollers. The Scenix offering was a bit special. In those days, the Microchip PIC was the king of the hill. The PIC is an odd beast that evolved from a very limited controller made to be small and inexpensive. Notably, while it could support relatively high clock frequencies — 20 MHz was common — each normal instruction took 4 clock cycles. So when your crystal said 20 MHz, you were running instructions at 5 MHz.

Continue reading “Chips Remembered: The Scenix/Ubicom/Parallax SX” →

The 286 Gives Up One Of Its Final Secrets

August 13, 2022 by Jenny List 115 Comments

Though it is largely forgotten today, the Intel 80286 was for a while in the 1980s the processor of choice and designated successor to the 8086 in the world of PCs. It brought a new mode that could address up to 16 Mb of memory, and a welcome speed boost over machines using an 8086 or 8088. As with many microprocessors, it has a few undocumented features, and it’s a couple of these that [rep lodsb] takes a look at. Along the way we learn a bit about the 286, and about why Intel had some of these undocumented instructions in the first place.

If you used a 286 it was probably as an end-user sitting in front of a PC-AT or clone. During manufacture and testing though, the processor had need of some extra functions, both for testing the chip itself and for debugging designs using it. It’s in these fields that the undocumented instructions sit, and they relate to an in-circuit emulator, a 286 with a debug port on some of its unused pins, which would have sat on a plug-in daughterboard for systems under test. The 286 was famous for its fancy extended mode taking rather a long time to switch to, and these instructions relate to loading and saving states before and after the switch.

The 286s time as the new hotness was soon blasted away by the 386 with its support for virtual memory, so for most of us it remains as simply a faster way that we ran 8086 code for a few years. They appear from time to time here, even being connected to the internet.

286 image: Thomas Nguyen (PttNguyen.net), CC BY-SA 4.0.

Want To Use A Classic Mac Mouse On A Modern Computer? No? Here’s How To Do It Anyway

August 11, 2022 by Donald Papp 23 Comments

Need to hook a classic Mac mouse up to your modern machine with the help of a DIY USB adapter? [John Floren] has you covered. [John]’s solution uses a board with an ATmega32U4 microcontroller on it to connect to the Mac mouse on one end, and emulate a USB HID (Human Interface Device) on the other. A modern machine therefore recognizes it like it would any other USB input device.

Why is this necessary? The connector on the classic Mac mouse may look like a familiar DE-9 connector, but it is not an RS-232 device and wouldn’t work if it were plugged into a 9-pin serial port. The classic Mac mouse uses a different pinout, and doesn’t have much for brains on the inside. It relies on the host computer to read its encoders and button states directly.

This project is actually a bit of an update to a piece of earlier work [John] did in making a vintage Depraz mouse work with modern systems. He suspected that it wouldn’t take much to have it also work with a classic Mac mouse, and he was right — all it took was updating the pin connections and adding some pull-up resistors. The source code and design files are on GitHub.

Even if one does not particularly want to use a classic Mac mouse for daily work, there’s definitely value in this kind of thing for those who deal in vintage hardware: it allows one to function-check old peripherals without having to fire up a vintage machine.

Continue reading “Want To Use A Classic Mac Mouse On A Modern Computer? No? Here’s How To Do It Anyway” →

Was There A Programmable PONG Chip?

August 8, 2022 by Jenny List 19 Comments

Students of game console history will reach back into the 1970s for the primordial machines, tracing from the Magnavox Odyssey onwards, and thence via the Fairchild Channel F into the world of microprocessors and the chain of machines that lead us to those we enjoy today. In the early days there was a parallel evolution for a few years of dedicated video game consoles with no interchangeable cartridges or microprocessors, these took their inspiration from the legendary PONG arcade game and used dedicated non-programmable hardware in custom chips to create their video. But was there a programmable PONG chip lurking among all the others? [Old VCR] takes a look.

Many readers will be familiar with MOS Technology as the originator of the 6502 processor used in so many 8-bit home computers. But perhaps many of our attention spans will have passed over another of their products, the MOS 7600 and 7601. These were the chip company’s entry into the surprisingly congested mid-70s PONG-in-a-chip market, and the article investigates the question of whether they might in fact be mask-programmed microcontrollers masquerading as dedicated chips.

It’s a fascinating tour through the mid-70s in terms of games consoles, MOS, and through their eventual takeover, Commodore. The possibility of a mask-programmed PONG chip is explored in detail and discounted, though like [Old VCR], we’d love to see one decapped and reverse engineered. For us a stronger line of evidence comes in asking why MOS would stop at PONG if they had a mask-programmed microcontroller in their catalogue, and that our not having seen MOS microcontrollers appearing all over Commodore’s subsequent products suggests that it may be simply another dedicated PONG chip like all the others.

We’ve seen quite a few variants of this iconic game over the years, but few as impressive as one made from discrete components.

Laptoppin’ Like 1975

August 6, 2022 by Al Williams 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” →

The GameTank Is The Latest And Greatest 8-bit Game Console

August 2, 2022 by Robin Kearey 16 Comments

The NES, Atari 2600, the Apple II, the Commodore 64 and the TurboGrafx-16 are just some of the many game consoles and home computers built around the 6502 CPU. And while the 6502 has been pretty much obsolete since the mid-’90s, that hasn’t stopped hackers from building new systems with it in the 21st century. Today we can even show you an entirely new 6502-based game console: the GameTank, designed and built by [Clyde Shaffer].

The GameTank was designed to be easy to build by anyone, and is therefore largely constructed from DIP chips that can be bought new at any component distributor. The main CPU is a WD65C02 running at 3.5 MHz, assisted by a 6522 I/O controller and 32 kB of RAM. Composite video is generated by a clever circuit made out of discrete logic chips. The video card comes with DMA for fast transfers and even includes a blitter, which enables it to move images around the screen quickly without loading the CPU.

For the controllers, [Clyde] decided to go for the more-or-less industry standard DE-9 connector gamepads as used on the Sega Genesis and various Atari consoles. He also made his own controller, a 3D printed one with four directional buttons, three action buttons and a start button. The buttons are implemented with Cherry MX Clear switches — an unusual choice for a gamepad perhaps, but they’re apparently very comfortable for long gaming sessions.

The console itself is also housed in a printed enclosure with a design reminiscent of the Nintendo 64. Game cartridges are inserted at the top and contain an EEPROM chip that can be written with a special programmer. The cartridge port also brings out several internal signals and can therefore be used as an expansion port, similar to the way Super NES cartridges could accommodate enhancement chips.

Games currently available include Tetris, the office-themed platformer Cubicle Knight, a Zelda-style adventure named Accursed Fiend, and a remake of the classic viral animation Bad Apple. [Clyde] provides a comprehensive stack of tools and example code and invites anyone interested to help develop more software for the platform. There’s also a hardware-accurate emulator, which is not only useful if you’re writing new code for the system but also if you simply want to try out the existing games in your browser.

Rolling your own 6502 system is great fun, and we’ve seen several examples over the years: some are built with huge bundles of wire, some are come with a clever programming language, some are so tiny they fit on your wrist, and some are simply beautifully made.

Continue reading “The GameTank Is The Latest And Greatest 8-bit Game Console” →