When Worlds Collide: 68008 Bootstrapped By An Arduino Uno

August 21, 2014 by Adam Fabio 23 Comments

68008-ardu

[Peter Bjornx] brings classic microprocessors and modern microcontrollers together with his Arduino bootstrapped 68008 computer. The Motorola 68008 is the 8-bit external bus version of the well-known 68000 (or 68k) microprocessor. A friend gave [Peter] one of these chips, so he built a simple computer around it.

This isn’t one of those clean retrocomputers with every connection carefully planned out and wire wrapped. [Peter’s] created a true hack – a working 68k system on a breadboard created with whatever he had on hand at the time. The real gem of this system is the ROM. [Peter] replaced an EPROM chip with an Arduino.

In the not-so-good-old-days, microprocessors (and many microcontrollers) ran from an external ROM chip. This often was a UV-erasable EPROM. Carefully compiled code was burned into the EPROM with a device programmer. If the code wasn’t perfect, the EPROM had to be pulled and placed under a UV lamp for 20 minutes or so to erase it before it was time to try again. EPROM emulators were available, but they were way too expensive for the hobbyist.

Thankfully those days are far behind us now with the advent of EEPROM and then Flash. [Peter] didn’t want to revisit the past either, so he wrote a simple Arduino sketch which allowed it to act as an EPROM emulator, including address logging via the serial port.

The design still caused [Peter] some headaches, though. His major problem was a classic 68k issue, /DTACK timing. /DTACK or Data Transfer Acknowledge is one of several bus control signals used by the 68k. When the 68k performs a read from the data bus, it waits for /DTACK before it transfers data. The Arduino was too slow to release /DTACK in this case, which caused the 68k to think every read was immediately completed. There is a much clearer explanation of the 68k bus cycles on this Big Mess O Wires page. [Peter’s] solution was simple – a D flip-flop connected to the address strobe took care of the timing issues.

It took quite a bit of tinkering, but the system eventually worked. Peter was able to run the 68008 from its reset vector into a simple loop using the Arduino. It’s only fitting that the 68k program loaded by the Arduino was an LED blinker, everyone’s favorite hardware Hello World.

Thanks [Robert!]

Hackaday 68k: So You Want A Kit?

March 27, 2014 by Brian Benchoff 67 Comments

68000

It’s yet another update to the Hackaday 68k, the wire-wrapped backplane computer that will eventually be serving up our retro site.

This is also a demo of Hackaday Projects, our new, fancy online documentation tool for all your adventures in making and tinkering. Did you know we’re having a contest on Hackaday Projects? Make something sci-fi, and you’re in the running for some really good prizes. There’s soldering stations, o-scopes, and a lot of other prizes being thrown at the winners. It’s awesome. First one to build a working Mr. Fusion wins.

In this update, I’m going to go over the beginnings of the video board, why Hammond enclosures are awesome and terrible at the same time, and some thoughts on turning this into a kit or product of some type. Click that, ‘Read more…’ link.

Continue reading “Hackaday 68k: So You Want A Kit?” →

Hackaday 68k: Gluing Architecture Buffer Maps

March 13, 2014 by Brian Benchoff 24 Comments

It’s time for more blatant advertising for Hackaday Projects, the best project hosting site on the Internet. Did we tell you it’s collaborative? That you and your friends can work on projects together? Want more encouragement to join? How about a contest with prizes that include oscilloscopes, FPGA dev boards, soldering and rework stations, Beaglebones and Raspberries and Spark Cores? Oh my!

Oh. We’re also developing a retrocomputer to show off the features of Hackaday Projects. This is the latest update, showing off the architecture of the entire system, the memory map, and the logic glue and buffers. The plan for this project is to have it host another awesome Hackaday site, our retro version, a small off-shoot of the main Hackaday site that’s specifically designed to be loaded by computers built before 1993. There haven’t been many retro successes in the Hackaday tip line recently, so if you manage to get a vintage computer to pull the retro site up, snap a pic and send it in.

For those of you wanting to catch up on the Hackaday 68k project, here’s the Hackaday Projects page, and here’s all the front page updates. Click that ‘Read more…’ link for the update.

Continue reading “Hackaday 68k: Gluing Architecture Buffer Maps” →

Hackaday 68k: Blinking An LED

March 5, 2014 by Brian Benchoff 47 Comments

Time for another update for the Hackaday 68k, the 16-bit retrocomputer developed on Hackaday to show off both our love for vintage hardware and our new project hosting site. There’s still invites to be had, people. Get ’em while they’re hot.

This post is going to cover exactly how complex a simple 68000 system is. The answer is, “not very.” A simple 68k system is at least as simple to design than some other homebrew systems we’ve seen around here. Yes, a 16-bit data bus means there’s more wires going everywhere, but like she said, just because it’s bigger doesn’t mean it’s harder.

There is some progress to report on the construction of the Hackaday 68k. The processor has been verified as working with a blinking LED. It’s the ‘Hello World’ of computer design, and it’s at least as complex as blinking a LED with an Arduino.

You’re gonna want to click that ‘Read more’ link.

Continue reading “Hackaday 68k: Blinking An LED” →

Hackaday 68k: Enclosure, Backplane, And Power

February 26, 2014 by Brian Benchoff 46 Comments

It’s about time for an update for Hackaday’s latest project – a modern retrocomputer based on the Motorola 68000 CPU. In this update, we’ll be taking a look at the enclosure, the backplane itself, and how we’re going to power this thing.

This is only an update to the project; you can check out the current status over on Hackaday Projects. It’s Hackaday’s new collaborative project hosting site where you (and your friends) can design, build, or document anything you have in mind. Request an invite for the alpha release of Hackaday Projects and you can give this project a skull! Seriously, this project is only the third ‘most skulled’ one on Hackaday Projects.

Now that the completely transparent pitch for Hackaday Projects is over with, we can get on to the update for the Hackaday 68k. Click that ‘Read More…’ link.

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Hackaday 68k: A New Hackaday Project

February 20, 2014 by Brian Benchoff 151 Comments

It’s no secret Hackaday loves retrocomputers, classic hardware, and vintage tech. Now that we have a great way to present long-form projects, it only makes sense that we combine our loves with a new build. Over the next few months, I’ll be developing a homebrew computer based on the Motorola 68000 CPU, documenting everything along the way, and building a very capable piece of hardware that will end up hosting a few Hackaday webpages. I already have a solid start on the project and will be posting on our front page to discuss the major parts already in progress, and those yet to come.

There are a few reasons we’re taking on this project. With few exceptions, most of the homebrew projects we see are based around 8-bit micros – specifically the 6502 and Z80. 16 and 32-bit CPUs really aren’t that much more difficult to work with, and if we can spearhead a renaissance of the 68k, 65816, or even a 386 (!), we’re all for that. Also, it’s been suggested that we host the Hackaday Retro site on retro hardware, and what better way to do that by documenting a build on our new project hosting site?

That’s a very brief introduction to this project. Let’s take a closer look at what hardware we’ll be using, what software we’ll get running, and what you can do to help.

Continue reading “Hackaday 68k: A New Hackaday Project” →

Ask Hackaday: Who Likes Retrocomputing?

September 15, 2012 by Brian Benchoff 54 Comments

Last week we posted a link to Project Kiwi, a homebrew Motorola 68008-based microcomputer built by [Simon] that includes Ethernet, a very good display adapter, an interface for IDE hard disks, two Commodore SID chips (for stereo chiptunes), a floppy disk controller, and an already existent software library that will make it very easy to develop your own software for this wonderful computer.

After thinking about [Simon]’s Project Kiwi for a while, I’ve been thinking there really hasn’t been a homebrew computer made that is so perfect for a proper Open Hardware release. There are more than enough peripherals in the computer to make development very fun. I’ve suggested doing a group buy to get Kiwi PCBs out into the wild and into the hands of other retrocomputer fanatics, but [Simon] would like a little more feedback.

Of course, this means turning to you, the wonderful Hackaday reader. Would any of you be interested in your own Kiwi microcomputer?

[Simon] tells me there are a lot of problems for turning the Kiwi microcomputer into a Open Hardware project. His prototype PCB cost €300, greatly reducing the number of people who would be interested in making their own Kiwi. Also, there are a few problems on the current PCB design (easily fixed for the next revision), and [Simon] would like to add a few features like DMA and a proper framebuffer.

Despite all those problems, I can’t see a better way to learn about computer architecture the hard way (i.e. 80’s microcomputers as opposed to futzing around with a Raspberry Pi). You’ll also get a really wonderful computer system that will show the power of 80s-era electronics, with the very hopeful goal of spreading the gospel of retrocomputing with the venerable Saint MC68000.

If you’d like to add your two cents – if having an Open Hardware 80s microcomputer is a good idea, or some technical requests such as adding a proper 68000 CPU to future designs, leave a note in the comments or on the forum [Simon] set up on his Kiwi page.

I think it’s a cool idea, but then again I’m probably blinded by how cool an 80s computer of this caliber is. The fate of this project is now in your hands.