computer hacks

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computer hacks

Restoring A Vintage PDP-11/04 Computer

April 8, 2015 by 22 Comments

[MattisLind] spent one and a half years to complete restoration of a Digital Equipment Corporation (DEC) PDP-11/04 including peripherals like a TU60 tape drive and a LA30P Decwriter printing terminal. The computer is now able to run CAPS-11 which is a very simple operating system and also CAPS-11/BASIC. Just like the project itself, his blog post is quite long filled with interesting details. For a tl;dr version, check the video after the break.

This system originally belonged to Ericsson and [MattisLind] received it from Ericsson computer club, EDKX. He was lucky to have access to online resources which made the task easier. But it still wasn’t easy considering the number of hardware faults he had to tackle and the software challenges too. The first task was obviously looking at the Power supply. He changed the big electrolytic capacitors, and the power supply seemed to work well with his dummy load, but failed when hooked up to the backplane of the computer. Some more digging around, and a replaced thyristor later, he had it fixed. The thyristor was part of a crowbar circuit to protect the system from over-voltages should one of the main switching transistors fail.

With the power supply fixed, the CPU still wouldn’t boot. Some sleuthing around, and he pin pointed the bus receiver chip that had failed. His order of the device via a Chinese ebay seller was on the slow boat, so he just de-soldered a device from another board which improved things a bit, but it was still stuck in a loop. A replacement communications board and the system now passed diagnostics check, but failed memory testing. This turned out to be caused be a faulty DIP switch. He next tackled all the software challenges in getting the CPU board up to speed.

Continue reading “Restoring A Vintage PDP-11/04 Computer” →

The Dan64: A Minimal Hardware AVR Microcomputer

April 7, 2015 by 26 Comments

[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” →

Fail Of The Week: Re-addressing Your RAM DIMM

April 5, 2015 by 14 Comments

It doesn’t work and we’re not surprised considering the can of worms that comes with RAM addressing. Right off the bat we assume timing problems due to variance in the trace lengths and EM issues. But you have to hand it to [cyandyedeyecandy] for even trying. The self-proclaimed upgrade seeks to readjust how the DIMM works without changing the edge pinout.

The stick shown here is a 512 MB module that, because of the computer using it (unspecified in the post), is only allowing access to 256 MB. The added chips and free-form circuit make up an AND for the chip-select line, and flip-flop for the bank address.

The post is a gorgeous cry for help. We already weighed in from the peanut gallery at the top (seriously, that’s somewhat baseless guessing) so step up to the computer-engineering plate and let us know what needs to be done to make this most-awesome-of-non-working hacks actually work.

Once you’ve figured this out, here’s another one to scratch at your brain with.

LEGO Computer Case

April 4, 2015 by 28 Comments

With over 40,000 pieces in his possession, [Mike] is definitely a huge fan of LEGO. Given that he’s also very much a fan of technology, it’s no surprise that he has built more than one type of LEGO computer case. He wrote in to tell us that he’s finished work on a well-rounded system designed for everyone.

[Mike] is no stranger to interesting case builds. In the last couple of years, he’s also made a functioning wind tunnel case and a bio computer that uses generated heat to warm soil for wheat grass plants. In the course of planning the LEGO computer, he thought a lot about heat and airflow, ultimately deciding on a top-down cooling path.

He’s quoting custom LEGO computer builds, providing the choice between an i3, i5, or i7 with either 8 or 16 gigs of RAM. They will run Linux or Windows 7/8 and are 10-compatible. There are a few choices for the top of the case: classic LEGO brick, the industrial look with diagonal slats, and a colored, tiled top. These systems are completely upgradeable and are held firmly together with great engineering and the occasional support rod.

laptop with external gpu

A Laptop With An External Graphics Card?

March 26, 2015 by 80 Comments

It used to be that desktop computers reigned king in the world of powerful computing, and to some extent, they still do. But laptops are pretty powerful these days, and in our experience, a lot of engineering companies have actually swapped over to them for resource hungry 3D CAD applications — But what if you still need a bit more power?

Well, [Kamueone] wasn’t satisfied with the performance of his Razer Blade GTX870m laptop, so he decided to hack it and give it its own external graphics card.

Now unfortunately this really isn’t quite a simple as running some PCIE extender cables — nope. You’ll have to modify the BIOS first, which according to [Kamueone], isn’t that bad. But after that’s done you’ll also need a way to mount your graphics card outside of the laptop. He’s using an EXP GDC Beast V6 which uses a mini PCIE cable that can be connected directly to the laptop motherboard. You’re also going to need an external power supply.

[Kamueone] ran some benchmarks and upgrading from the stock onboard GTX870m to an external GTX 780ti resulted in over three times the frame rate capability — 40fps stock, 130fps upgraded!

Hard Drive Becomes Hard Drive Activity Light; Stores No Data

March 15, 2015 by 20 Comments

A while ago [Frank Zhao] built a computer in an aquarium. It’s exactly what you would expect – a bunch of parts stuffed into a container filled with mineral oil. Yes, there’s an i7 and a GTX970 in there, but there’s also a bunch of neopixels and a neat little bubbling treasure chest. That wasn’t enough for [Frank], and he wanted to add a HDD activity monitor. What’s the most absurd activity monitor for an SSD? An old platter-based drive, of course.

The build is relatively simple and something [Frank] put together from spare parts in a day. After cracking open an old PATA hard drive, the voice coil for the hard drive arm was connected to the motherboard’s HDD activity signal through a few MOSFETs. The platter motor is controlled by an MTD6501 motor driver, set to spin up when the circuit is on.

It’s a kludge as far as controlling the components of a hard drive go, but that’s not really the point. It’s just a neat project to show when the SSD in the aquarium computer is being accessed. That said, the activity monitor is currently disconnected because the old HDD is so freakin’ loud. It looks really cool, though.

minimalist desk

Sliding Minimalist Computer Desk Starts Life As Ikea Shelf

February 20, 2015 by 33 Comments

Where are you right now? You’re probably sitting at a desk staring at a computer screen. Us tinkerers/makers/hackers/diyers use computers all the time… they are a great tool and an easy way to spread and gather information. Since we spend so much time sitting at a computer, why shouldn’t the computer’s desk be made to enhance the experience?

Self-proclaimed web guru [Ellis] admits to being a minimalist and wanted a super sleek computer desk. He couldn’t find a commercially available model that he liked so he built his own.

The desk started as an Ikea floating shelf. The shelf comes with a metal bracket that secures to a wall, then the shelf completely slides over the bracket so that the shelf looks as if it is floating in air. Once the u-shaped bracket was installed to the wall, a custom compartment was made to fit in between the bracket’s arms. This compartment will hold a power strip, mini Dell computer and other accessories. On the outside of each bracket arm, [Ellis] mounted drawer slides. The stock shelf was then modified to mount to the newly added drawer slides allowing it to be pulled forward for typing or to expose the hidden compartment. When closed, the shelf-desk looks clean and blends into the wall color.

A wide screen monitor is mounted directly on the wall just above the desk and a wireless keyboard/mouse combo supports the clean look. [Ellis] now has the minimalist computer desk he’s always wanted that doesn’t distract him from his work (or ‘net browsing).