ZX81 Emulated On An Mbed

December 22, 2014 by Bryan Cockfield 7 Comments

This is a wonderful example of the phenomenon of “feature creep”. [Gert] was working on getting a VGA output running on an mbed platform without using (hardly) any discrete components. Using only a few resistors, the mbed was connected to a VGA display running at 640×480. But what could he do with something with VGA out? He decided to emulate an entire Sinclair ZX81 computer, of course.

With more than 1.5 million units sold, the Sinclair ZX81 was a fairly popular computer in the early ’80s. It was [Gert]’s first computer, so it was a natural choice for him to try to emulate. Another reason for the choice was that his mbed-VGA device could only output monochrome color, which was another characteristic of the ZX81.

[Gert] started by modifying a very lean Z80 emulator to make the compiled code run as efficiently as possible on the mbed. Then he went about getting a picture to display on the screen, then he interfaced an SD card and a keyboard to his new machine. To be true to the original, he built everything into an original ZX81 case.

This isn’t the first time we’ve seen a ZX81, but it is one of the better implementations of an emulated version of this system we’ve seen.

Thanks to [Jeroen] for the tip!

The KIM-1 Computer Minified

November 7, 2014 by Brian Benchoff 18 Comments

The KIM-1 wasn’t the first microcomputer available to computer hobbyists and other electron aficionados, but it was the first one that was cheap. It was also exceedingly simple, with just a 6502 CPU, a little more than 1k of RAM, 2k of ROM, a hexadecimal keypad and a few seven-segment displays. Still, a lot of software was written for this machine, and one of these boards can be found in every computer history museum.

[Oscar] thought the KIM-1 was far too cool to be relegated to the history books so he made his own. It’s not a direct copy – this one uses an Arduino for the brains, only breaking out some buttons, a pair of four-digit seven-segment displays, and the I2C and SPI pins on the ‘duino. The KIM-1 is emulated by the Arduino, allowing for the same interface as an original connected up to an old teletype, and [Oscar] got his hands on the original code for Microchess and the first 6502 disassembler from [Woz] and [Baum].

[Oscar] put the schematics for his version of the KIM-1 up, and has the PCBs up on SeeedStudio. If you’re looking for an awesome replica of a vintage computer and a nice weekend project, here ‘ya go.

Restoring A PDP-10 Console Panel

October 28, 2014 by Brian Benchoff 27 Comments

The PDP-10 was one of the first computers [Jörg] had gotten his hands on, and there are very, very few people that can deny the beauty of a panel full of buttons, LEDs, dials, and analog meters. When one of the front panels for a PDP-10 showed up on eBay, [Jörg] couldn’t resist; a purchase that would lead him towards repairing this classic console and making it functional again with a BeagleBone.

The console [Jörg] picked up is old enough to have voted for more than one Bush administration, and over the years a lot of grime has covered the beautiful acrylic panels. After washing the panel in a bathtub, [Jörg] found the dried panel actually looked worse, like an old, damaged oil painting. This was fixed by carefully scraping off the clear coat over two weeks; an important lesson in preserving these old machines. They’re literally falling apart, even the ones in museums.

With the front panel cleaned, [Jörg] turned his attention to the guts of this panel. The panel was wired up for LEDs, and each of the tiny flashlight bulbs in the pushbuttons were replaced. The panel was then connected to a BlinkenBone with a ton of wiring, and the SIMH simulator installed. That turns this console into a complete, working PDP-10, without sucking down kilowatts of power and heating up the room

This isn’t the first time we’ve seen [Jörg] with a BeagleBone and some old DEC equipment; earlier he connected the front panel of a PDP-11 variant to one of these adapters running the same software.

Thinkpad 701c: Reverse Engineering A Retro Processor Upgrade

October 21, 2014 by Adam Fabio 37 Comments

[Noq2] has given his butterfly new wings with a CPU upgrade. Few laptops are as iconic as the IBM Thinkpad 701 series and its “butterfly” TrackWrite keyboard. So iconic in fact, that a 701c is part of the permanent collection of the Museum of Modern Art in New York.

Being a 1995 vintage laptop, [Noq2’s] 701c understandably was no speed demon by today’s standards. The fastest factory configuration was an Intel 486-DX4 running at 75 MHz. However, there have long been rumors and online auctions referring to a custom model modified to run an AMD AM-5×86 at 133 MHz. The mods were performed by shops like Hantz + Partner in Germany. With this in mind, [Noq2] set about reverse engineering the modification, and equipping his 701c with a new processor.

The first step was determining which AMD processor variant to use. It turns out that only a few models of AMD’s chips were pin compatible with the 208 pin Small Quad Flat Pack (SQFP) footprint on the 701c’s motherboard. [Noq2] was able to get one from an old Evergreen 486 upgrade module on everyone’s favorite auction site. He carefully de-soldered the AM-5×86 from the module, and the Intel DX4 from the 701c. A bit of soldering later, and the brain transplant was complete.

Some detailed datasheet research helped [noq2] find the how to increase the bus clock on his 5×86 chip, and enable the write-back cache. All he had to do was move a couple of passive components and short a couple pins on the processor.

The final result is a tricked out IBM 701c Thinkpad running an AMD 5×86 at 133 MHz. Still way too slow for today’s software – but absolutely the coolest retro mod we’ve seen in a long time.

A PC Engine To TurboGrafx-16 Converter

October 10, 2014 by Brian Benchoff 23 Comments

The PC Engine was pretty popular in Japan, but only the coolest kids in America had the US edition, the TurboGrafx16. These two systems weren’t exactly the same; the TurboGrafx-16’s data bus was flipped so the games were made to be incompatible, and the US games have a region lockout. [Kaz] looked at the existing hacks for running Japanese games on US systems, and every single one of them required modding a console. Thinking he could do better, he came up with the PC-Henshin, an adapter and CPLD that allows Japanese game to run on US consoles.

To take care of the mixed up lines on the PC card connector between the US and Japanese variants, a few adapter cards are available. That’s great, but they only solve one part of the compatibility problem. The region lockout routine found on nearly every American title mean PC Engine consoles can’t run TurboGrafx-16 games. [Kaz] used a small, cheap CPLD to read the data bus, patch everything as it is read out, and turns a Japanese console into something that can play American games.

Video below.

Continue reading “A PC Engine To TurboGrafx-16 Converter” →

Build Your Own Retrocomputer With Modern Chips

September 16, 2014 by Bryan Cockfield 27 Comments

If you’ve ever wanted to get started in retrocomputing, or maybe the Commodore 64 you’ve been using since the 80s just gave up the ghost, [Rick] aka [Mindrobots] has just the thing for you: a retrocomputer based on a PIC microcontroller and a Parallax Propeller.

The two chips at the heart of the computer are both open source. The Propeller is the perfect board to take care of the I/O, video, and audio outputs because it was purpose-built to be a multitasking machine. The microcontroller is either a PIC32MX150 or a PIC32MX170 and is loaded with a BASIC interpreter, 19 I/O pins, a full-screen editor, and a number of communications protocols. In short, everything you would ever want out of a retro-style minicomputer.

The whole computer can be assembled on a PCB with all the outputs you can imagine (VGA, PS/2, etc) and, once complete, can be programmed to run any program imaginable including games. And, of course, it can act as a link to any physical devices with all of its I/O because its heart is a microcontroller.

Retrocomputing is quite an active arena for hackers, with some being made from FPGAs and other barebones computers being made on only three chips. It’s good to see another great computer in the lineup, especially one that uses open chips like the Propeller and the PIC.

Hackaday Retro Edition: 386 Compaqs

September 1, 2014 by Brian Benchoff 28 Comments

[Antoine] recently learned of a little challenge we have in the hinterlands of the Hackaday webosphere – what’s the oldest, or lowest spec hardware you have that can load this our retro edition? He has a pile of old PCs at his work, and with a lot of idle time at work because of summer, he decided to dig into that pile and get a really old computer up on the Internet.

While the pile of PCs didn’t have anything as old as he was expecting, [Antoine] did find an old Compaq from 1992. It has a 386DX running at 25MHz, 4MB of RAM, a 300 MB hard drive, VGA, and an Ethernet NIC. Gathering the requisite CRT monitor, PS/2 keyboard, and an AUI to a more modern Ethernet connector.

When getting these ancient computer on the Internet, the secret sauce is in the software configuration. [Antoine]’s box is running DOS 6.2, but was previously configured to connect to a Microsoft filesystem server on boot. This server was probably somewhere at the bottom of the same pile the Compaq was salvaged from, so rolling his own modern networking stack was the way to go. A driver for the NIC was downloaded on another computer and transferred via floppy, as was mTCP, the key to getting a lot of old PCs on the Internet. The browser is Arachne, and with the right configurations, everything worked perfectly.

[Antoine]’s efforts resulted in a computer that can easily handle the stripped down Hackaday retro edition, and can handle light browsing on Wikipedia. The effective download rate is something like a 33k modem; even with a fast (10M!) Ethernet connection, processing all the packets is taxing for this old machine.