The Q2, A PDP8-Like Discrete Transistor Computer

February 6, 2022 by Dave Rowntree 39 Comments

[Joe Wingbermuehle] has an interest in computers-of-old, and some past experience of building computers on perfboard from discrete transistors, so this next project, Q2, is a complete implementation of a PDP8-like microcomputer on a single PCB. Like the DEC PDP-8, this is a 12-bit machine, but instead of the diode-transistor logic of the DEC, the substantially smaller Q2 uses a simple NMOS approach. Also, the DEC has core memory, but the Q2 resorts to a pair of SRAM ICs, simply because who wants to make repetitive memory structures with discrete 2N7002 transistors anyway?

SMT components for easy machine placement

Like the PDP-8, this machine uses a bit-serial ALU, which allows the circuit to be much smaller than the more usual ALU structure, at the expense of needing a clock cycle per bit per operation, i.e. a single ALU operation will take 12 clock cycles. For this machine, the instruction cycle time is either 8 or 32 clocks anyway, and at a maximum speed of 80 kHz it’s not exactly fast (and significantly slower than a PDP-8) but it is very small. Small, and perfectly formed.

The machine is constructed from 1094 transistors, with logic in an NMOS configuration, using 10 K pullup resistors. This is not a fast way to build a circuit, but it is very compact. By looking at the logic fanout, [Joe] spotted areas with large fanouts, and reduced the pull-up resistors from 10 K to 1 K. This was done in order to keep the propagation delay within bounds for the cycle time without excessive power usage. Supply current was kept to below 500 mA, allowing the board to be powered from a USB connector. Smart!

Memory is courtesy of two battery-backed 6264 SRAMs, with the four 12-bit general purpose registers built from discrete transistors. An LCD screen on board is a nice touch, augmenting the ‘front panel’ switches used for program entry and user input. A 40-pin header was added, for programming via a Raspberry Pi in case the front panel programming switches are proving a bit tedious and error prone.

Discrete transistor D-type flip flop with indicator. Latest circuit switched to 2N7002 NMOS.

In terms of the project write-up, there is plenty to see, with a Verilog model available, a custom programming language [Joe] calls Q2L, complete with a compiler and assembler (written in Rust!) even an online Q2 simulator! Lots of cool demos, like snake. Game of Life and even Pong, add some really lovely touches. Great stuff!

We’ve featured many similar projects over the years; here’s a nice one, a really small 4-bit one, and a really big one.

IBM PalmTop Running Modern (Modified) Linux

February 6, 2022 by Bryan Cockfield 19 Comments

The handheld computing market might seem dominated by smartphones today, but before their mass adoption there were other offerings for those who needed some computing power on-the-go. If a 90s laptop was too bulky, there was always the IBM PalmTop which packed punch for its size-to-weight ratio, and for the era it was created in. [Mingcong Bai] still has one of these antiques and decided to see if it was still usable by loading a customized Linux distribution on it.

The PalmTop sported modest hardware even for its time with an Intel 486SL running at 33 MHz with 20 MiB of RAM. This one also makes use of a 1 GB CompactFlash card for storage and while [Mingcong Bai] notes that it is possible to run Windows 95 on it, it’s not a particularly great user experience. A Linux distribution customized for antique hardware, AOSC/Retro, helps solve some of these usability issues. With this it’s possible to boot into a command line and even do some limited text-based web browsing as long as the Ethernet adapter is included.

While the computer is running at its maximum capacity just to boot and perform basic system functions, it’s admirable that an antique computer such as this still works, especially given its small size and limited hardware functionality. If you’re curious about more PalmTop-style computers, take a look at the first one ever produced: the HP-200LX.

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The Fifteen Dollar Linux Computer

February 4, 2022 by Jenny List 66 Comments

Over the years we’ve seen many small computer boards of various abilities, among them many powerful enough to be almost-useful Linux general purpose computers. We’ve also seen more than a few computers that claimed the impossible, usually an amazing spec for a tiny price tag. Here for once is a small computer that’s neither of those two; a minimum viable Linux handheld terminal whose $15 USD price tag is openly discussed as a target price for a large production run rather than touted as its retail price.

It’s the work of legendary former Hackaday writer [Brian Benchoff], and instead of being merely a PCB it’s a fully usable computer with case, keyboard and display. It’s based upon an Allwinner F1C100s SoC, it’s powered by AAA cells, and it sports a split rubber keyboard that likely builds on his previous experience with the VT-69 portable RS-232 terminal. On the back is a USB port and an SD reader, and in the centre of the front panel lies a 320 x 240 pixel display. It’s important to note that this is not intended to run a GUI, while it’s DOOM-capable it remains very much a command-line Linux tool. Perhaps most interestingly it’s claimed that all the parts are available in quantity here in the chip shortage, so maybe there’s even a chance we might see it as more than a project. We can hope.

Thanks [Sathish Guru V] for the tip.

A Portable Projecting Pi For Education

February 2, 2022 by Jenny List 16 Comments

We cover a lot of cyberdeck projects here at Hackaday, custom portable computers often built around the Raspberry Pi. It’s not often that we cover a computer that perfectly achieves and exceeds what a cyberdeck is trying to do without being a cyberdeck in any way, but that’s what [Subir Bhaduri] has done. In addressing the need for Indian schoolchildren to catch up on two years of COVID-disrupted schooling he’s created the pπ, a Raspberry Pi, projector, and keyboard all-in-one computer in a neat sheet-metal case that looks as though it might be just another set of spanners or similar. At a stroke he’s effortlessly achieved the ultimate cyberdeck, because this machine is no sci-fi prop, instead it has a defined use which it fulfills admirably.

All the files to build your own can be found in a GitLab repository. The case is laser-cut sheet metal, and he’s put in a cost breakdown which comes out at a relatively healthy 17200 Indian rupees, or around 230 US dollars. We hope that it serves its purpose well and provides a rugged and reliable teaching aid for a generation from whom COVID has taken so much. You can see more in the video below the break.

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Analog Computer Made From LEGO Predicts Tides

February 1, 2022 by Robin Kearey 4 Comments

Although the tides in the ocean are caused by the motion of the Sun and the Moon, both of which are easy to observe, accurately predicting the tide more than a few days in advance turns out to be rather difficult. The math behind the tidal movement is so complex that some of the earliest analog computers were built specifically to perform tide calculations. Sir William Thomson (better known as Lord Kelvin) designed one such “tide-predicting machine”, an impressive arrangement of gears and pulleys, back in the late 19th century.

[Pepijn de Vos] built a modern interpretation of Thomson’s machine out of LEGO parts, and it’s no less impressive than the original. A total of 96 LEGO gears move perfectly in sync to the ocean’s natural rhythms, while a set of pulleys connect four banks of gears together to create the sum of the constituent frequencies. An ultrasonic sensor reads the output value and sends the result back to a PC.

One interesting problem that [Pepijn] ran into, and which he explains in great detail on his blog, is that LEGO gears can only provide a very limited set of gear ratios. In order to match the tide calculations to any kind of precision, he needed to connect many gears in series without creating too much friction and backlash in the mechanism. Optimizing this setup was a non-trivial task that required a significant amount of computing power by itself.

As you can see in the video embedded below, the machine makes beautifully smooth movements, which correspond quite accurately to the actual motion of tides. If you’re interested in the science behind analog tide predictors, we’ve got an in-depth article about just that.

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A HP Proliant 360 g6 server with its lid taken off, showing separate green wires coming out of every fan, enabling Dave's modification

Domesticating Old Server Hardware In The Age Of Shortages

January 24, 2022 by Arya Voronova 20 Comments

Our own [Dave Rowntree] started running into bottlenecks when doing paid work involving simulations of undisclosed kind, and resolved to get a separate computer for that. Looking for budget-friendly high-performance computers is a disappointing task nowadays, thus, it was time for a ten-year-old HP Proliant 380-g6 to come out of Dave’s storage rack. This Proliant server is a piece of impressive hardware designed to run 24/7, with a dual CPU option, eighteen RAM slots, and hardware RAID for HDDs; old enough that replacement and upgrade parts are cheap, but new enough that it’s a suitable workhorse for [Dave]’s needs!

After justifying some peculiar choices like using dual low-power GPUs, only populating twelve out of eighteen RAM slots, and picking Windows over Linux, [Dave] describes some hardware mods needed to make this server serve well. First, a proprietary hardware RAID controller backup battery had to be replaced with a regular NiMH battery pack. A bigger problem was that the server was unusually loud. Turns out, the dual GPUs confused the board management controller too much. Someone wrote a modded firmware to fix this issue, but that firmware had a brick risk [Dave] didn’t want to take. End result? [Dave] designed and modded an Arduino-powered PWM controller into the server, complete with watchdog functionality – to keep the overheating scenario risks low. Explanations and code for all of that can be found in the blog post, well worth a read for the insights alone.

If you need a piece of powerful hardware next to your desk and got graced with an used server, this write-up will teach you about the kinds of problems to look out for. We don’t often cover server hacks – the typical servers we see in hacker online spaces are full of Raspberry Pi boards, and it’s refreshing to see actual server hardware get a new lease on life. This server won’t ever need a KVM crash-cart, but if you decide to run yours headless, might as well build a crash-cart out of a dead laptop while you’re at it. And if you decide that running an old server would cost more money in electricity bills than buying new hardware, fair – but don’t forget to repurpose it’s PSUs before recycling the rest!

Identifying Malware By Sniffing Its EM Signature

January 19, 2022 by Tom Nardi 17 Comments

The phrase “extraordinary claims require extraordinary evidence” is most often attributed to Carl Sagan, specifically from his television series Cosmos. Sagan was probably not the first person to put forward such a hypothesis, and the show certainly didn’t claim he was. But that’s the power of TV for you; the term has since come to be known as the “Sagan Standard” and is a handy aphorism that nicely encapsulates the importance of skepticism and critical thinking when dealing with unproven theories.

It also happens to be the first phrase that came to mind when we heard about Obfuscation Revealed: Leveraging Electromagnetic Signals for Obfuscated Malware Classification, a paper presented during the 2021 Annual Computer Security Applications Conference (ACSAC). As described in the mainstream press, the paper detailed a method by which researchers were able to detect viruses and malware running on an Internet of Things (IoT) device simply by listening to the electromagnetic waves being emanated from it. One needed only to pass a probe over a troubled gadget, and the technique could identify what ailed it with near 100% accuracy.

Those certainly sound like extraordinary claims to us. But what about the evidence? Well, it turns out that digging a bit deeper into the story uncovered plenty of it. Not only has the paper been made available for free thanks to the sponsors of the ACSAC, but the team behind it has released all of code and documentation necessary to recreate their findings on GitHub.

Unfortunately we seem to have temporarily misplaced the $10,000 1 GHz Picoscope 6407 USB oscilloscope that their software is written to support, so we’re unable to recreate the experiment in full. If you happen to come across it, please drop us a line. But in the meantime we can still walk through the process and try to separate fact from fiction in classic Sagan style.

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