A one-bit processor

Put on that abstract thinking cap, get out the pen and paper, and spend some time figuring out how this one-bit processor works. [Strawdog] came up with the concept one day during his commute to work (don’t worry, he takes the train… much safer than [Dave Jones’] frightening drive-time podcasts). He sketched it out on paper to make sure he knew where he was going with the project, then collaborated with Legion Labs to implement it in processing as an easier way to visualize its functionality. Since it’s one-bit there’s only room for one instruction. That instruction is a copy, then branch-if instruction. It copies the current bit to one address, and if that bit was one, it branches to a second address.

Going a bit fast for you? We think the description is fairly good, but if you can’t quite put it together from the article’s description, you may want to build this 2-bit paper processor and learn how it works first. It should teach you the basic concepts you need to understand the 1-bit version. As you can see in the image above, there’s also a single-step feature in the processing example that lets you analyze the effects of each instruction during program execution.

The Origin of the Arduino

If you ever wondered how the Arduino came into being, check out [IEEE Spectrum’s] article entitled “The Making of Arduino.” From it’s humble origins in Northern Italy, the Arduino, as shown by a large number of projects featured at [HAD], has become the go-to processor for DIY processing power. It’s cost (around $30) and ease-of-use are some of the biggest factors allowing it to become such a huge success.

One thing that interests many people about the Arduino is that it is totally open source, licensed under the Creative Commons License.  This was quite innovative in itself since the CCL was generally applied to works of art like music and writing.  Despite the fact that [Banzi] and his team decided to literally give the design away, 0ver 250,000 of these boards have been sold worldwide not including their many clones.

If you’re wondering how it got the name “Arduino”, it’s named after a bar named “Bar Di Re Arduino” in the Northern Italian town of Ivrea.

Debug mode lurking inside AMD chips

Looks like some hardware enthusiasts have worked out a method to enable debug mode within AMD processors. The original site isn’t loading for us, but the text has been mirrored in this comment. Getting the chip into debug mode requires access passwords on four control registers. We’ve read through the writeup and it means very little to us but we didn’t pull out a datasheet to help make sense of the registers being manipulated. It shouldn’t be hard to find an old AMD system to try this out on. We’d love to hear about anything you do with this debug system.

[via Slashdot]

2-bit paper processor teaches how they work

Take a few minutes out of your day, grab your scissors, and learn how a simple processor works. [Saito Yutaka] put together an exercise to teach processor operations with paper. After downloading the PDF you can cut out the Address and Data pointer as well as two-bit data tokens for each. The processor has three instruction sets; Increment register by one, Jump if not over flow, and Halt wait for reset.

Once you’ve got your cutouts you can follow along as the program is executed. The INC operation is run, with the JNO used to loop the program. Once the register has reached an overflow the overflow counter halts the program.

One word of warning, we think there’s a typo in one of the captions.  Once the program starts running and gets to address 01(2) the caption still reads 00(2) for both address and data. As long as you compare the values in the picture along the way you should have no problem getting through execution. which has now been fixed.

Peering in a the A4, the iPad’s brain

Sure, tearing down devices to see what components are in there is fun. But tearing down the components themselves is even more fun. iFixit sent off their iPad guts to be laid bare after they were done with their iPad teardown. We’ve seen pictures of stripped chips in the past, but the work that Chipworks is doing for iFixit is quite amazing. Get the skinny on just about every part in there from the package markings and the die photos provided in their analysis.

The iPad has already been rooted, but you never know what power can be unlocked if you know what you’re working with. We’re thinking of the 50MHz to 100Mhz oscilloscope hack.

Processor built with Transistor-Transistor Logic


[Donn] wanted know exactly what is going on inside of a processor so naturally he built a CPU out of TTL components. He had previously built a couple of versions of a computer based on the Z80 processor. Using the troubleshooting skills he learned and a second-hand textbook, he set to work using 74LS series chips connected using the wire-wrap method we’re familiar with from other cpu projects.

The finished product runs well at 1.8 megahertz, but he also included a 2 hertz clock and a step clock for debugging. At the slower speeds, the register board (seen at the left in the picture above) lights LEDs and can be used to tell what the CPU is currently working on. Programming is accomplished through either  a dumb terminal or a PC running a terminal emulator.

His writeup is from about five years ago but that didn’t prevent us from getting that fuzzy feeling in the geek-center of our brain when we read about it. It is well written and thorough so if you’re into this kind of thing there’s plenty to enjoy.

[Thanks Raleigh]

NES processor cloned on a FPGA


[Bradley] decided to tackle the challenge to recreate the original Nintendo Entertainment System’s processor in a Field Programmable Gate Array. Say what? The original NES is a Legacy System, still used but no longer manufactured. If a system breaks, it becomes more and more difficult to repair or find replacements parts as time passes. By using a programmable integrated circuit such as a CPLD or a FPGA to clone the functionality of the original hardware, legacy systems can live on long after the original hardware has given up the ghost.

It took [Bradley] about a year to fully implement the NES processor as part of his Master’s project at Bradley University. He used what was known about the processor combined with some detective work with logic probes along the way. The programming was done in VHDL and those files are available for download (click on Documentation).

With the ubiquity of NES emulators on every device known to man you probably won’t be replicating this unless you want a reason to play with a FPGA. What interests us is the hardware solution this type of work provides for obsolete hardware that still serves a useful purpose. If you’ve used a FPGA or similar device to keep an old system running, let us know about it in the comments.