Decoding The 8088

October 9, 2023 by Al Williams 2 Comments

There is a lot to like about open software, and in some areas, a well-thought-out piece of software can really make a huge impact. A great example of this is the Sigrok project. Creating simple devices that act like a logic analyzer is relatively easy. What’s hard is writing nice software for such a setup including protocol decoders. Sigrok has done it and since it is open, you can add your device and decode your protocol. [GloriousCow] had done the hardware part of interfacing to the 8088 in an IBM PC using an off-the-shelf logic analyzer that uses a customized version of Sigrok. But the output was a CSV file you had to process in a spreadsheet program. The next step: write a decoder for Sigrok to understand 8088 bus cycles.

The post covers the details of writing such a plug-in for Pulseview, the Sigrok GUI. It will also work for the command line interface if you prefer that. The code is in Python.

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Implementing Commodore’s IEC Bus Protocol On A KIM-1 Single Board Computer

October 7, 2023 by Maya Posch 3 Comments

Although the PET is most likely the more well-known of Commodore’s early computer systems, the KIM-1 (Keyboard Input Monitor) single board computer was launched a year prior, in 1976. It featured not only the same MOS 6502 MPU as later Commodore systems, but also an MCS6530 PIO IC that contained the ROM, RAM and programmable I/O, reminiscent of later I/O chips on Commodore systems. As the KIM-1 was only designed to be used with an external tape drive (and a terminal for fancy users), adding a floppy drive like the ubiquitous 1541 with its IEC bus interface was not a first-party accessory. How the IEC bus can be retrofitted to a KIM-1 system is demonstrated in this video by the Commodore History channel.

The Commodore KIM-1 hardware is almost directly compatible with the C64 hardware. (Credit: Commodore History on YouTube)

What is most notable is just how similar the KIM-1 hardware is to later PET and VIC hardware, with the CIA and PIO ICs featuring the same requisite pins for this purpose, and requiring only the addition of an inverting (SN7406) IC and an EPROM featuring the new code to support the proprietary Commodore IEC bus protocol, which was mostly pilfered byte-for-byte from a C64 kernal ROM.

With some creative breadboarding in place and using nothing more than the on-board LED display and keyboard matrix, it was then possible to write to the inserted floppy disk, and also to read back from it. What’s interesting here is that this essentially replaces the tape drive as target for the KIM-1, which thus retains a lot of the original functionality, but with a big performance boost. While perhaps only interesting as an academic exercise, it’s definitely an interesting look at the early beginnings of what would blossom into the Commodore 64.

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CPU Built From Discrete Transistors

September 30, 2023 by Bryan Cockfield 29 Comments

We all know, at least intellectually, that our computers are all built with lots of tiny transistors. But beyond that it’s a little hard to describe. They’re printed on a silicon wafer somehow, and since any sufficiently advanced technology is indistinguishable from magic, they miraculously create a large part of modern society. Even most computers from 40 or 50 years ago were built around various inscrutable integrated circuits. On the other hand, this computer goes all the way back to first principles and implements a complete processor out of individual transistors instead.

The transistor computer uses over 2000 individual transistors to implement everything comprising the 11-bit CPU. The creator, Reddit user [ Weekly_Salamander_78] also has an online interactive book that walks through each of the steps that is required to get to the point of having a working computer like this. Starting with a guide on building logic gates from transistors it will eventually cover the arithmetic logic unit, adders, memory, clocks, and everything else that is needed for the complete CPU to get up and running. The design does rely on an Arduino for memory to simplify some things, and in the end it’s able to run a Hello, World! program and play a simple dinosaur game as well.

Building a computer out of discrete components like this is an impressive accomplishment, although we might not envy the creator of it when it comes time for troubleshooting or maintenance of all of those individual components. Presumably it would be much easier to work on than something like a relay computer, but for now we’ll all take a moment to be thankful that almost no one needs to work on debugging vacuum tube computers anymore.

TMD-3: Clever Hall Sensor Hack Leads To Better Turing Demo

September 20, 2023 by Dan Maloney 4 Comments

We’ll beat everyone to the punch: yes, actually building a working Turing machine, especially one that uses a Raspberry Pi, is probably something that would have pushed [Alan Turing]’s buttons, and not in a good way. The Turing machine is, above all else, a thought experiment, an abstraction of how a mechanical computing machine could work. Building a working one seems to be missing the point.

Thankfully, [Michael Gardi] has ignored that message three times now, and with good reason: some people just grok abstract concepts better when they can lay their hands on something and manipulate it. His TMD-1 was based on 3D printed tiles with embedded magnets — arranging the tiles on a matrix containing Hall effect sensors programmed the finite state machine, with the “tape” concept represented by a strip of eight servo-controlled flip cards. While TMD-1 worked fine, it had some limitations, which [Mike] quickly remedied with TMD-2, a decidedly more complicated affair that used a Raspberry Pi, a camera, and OpenCV to read an expanded state machine with six symbols and six states, without breaking the budget on all the Hall sensors required.

TMD-3 refines the previous design, eschewing the machine vision approach and returning to the Hall effect roots of the original. But instead of using three sensors per tile, [Mike] determined that one sensor would suffice as long as he could mount the magnet at different depths within each tile. That way, the magnetic field for each symbol could be discerned by a single Hall sensor, greatly reducing complexity and expense. An LCD screen and a Raspberry Pi run a console app that shows the tape status, the state machine, and the state transitions.

[Mike] put a ton of work into this one — there are nineteen project logs — and he includes a lot of useful tips and tricks, like designing PCBs directly in KiCAD before even having a schematic. Of course, with a track record like his, we’d expect nothing less.

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Chromebooks Now Get Ten Years Of Software Updates

September 17, 2023 by Jenny List 48 Comments

It’s an acknowledged problem with the mobile phone industry and particularly within the Android ecosystem, that the operating system support on a typical device can persist for far too short a time, leaving the user without critical security updates. With the rise of the Chromebook, this has moved into larger devices, with schools and other institutions left with piles of what’s essentially e-waste.

Now in a rare show of sense from a tech company, Google have announced that Chromebooks are to receive ten years of updates from next year. Even better, it seems that this will be retroactively applied to at least some older machines, allowing owners to opt in to further updates for the remainder of the decade following the machine’s launch.

Of course, a Chrome OS upgrade on an older machine won’t make it any quicker. We’re guessing many users will feel the itch up upgrade their hardware long before their decade of software support is up. But anything which saves e-waste has to be applauded, and since this particular scribe has a five-year-old ASUS Transformer just out of support, we’re hoping for a chance to jump back on that train.

There’s another question though, and it relates to the business model behind Chromebooks. We doubt that the hardware manufacturers are thrilled at their customers’ old machines receiving a new lease of life and we doubt Google are doing this through sheer altruism, so we’re guessing that the financial justification comes from an extra five years of making money from the users’ data.

The motherboard of a Mattel Aquarius, with a small daughterboard mounted on top

Adding Composite Video To The Mattel Aquarius

September 8, 2023 by Robin Kearey 14 Comments

In the home computer market of the 1980s, there were several winners that are still household names four decades later: the Commodore 64, the Apple II and the Sinclair Spectrum, to name a few. But where there are winners, there are bound to be losers as well – the Mattel Aquarius being a good example. A price war between the bigger players, combined with a rather poor hardware design, meant that the Aquarius was discontinued just a few months after its introduction in 1983. However, this makes it exactly the type of obscure machine that [Leaded Solder] likes to tinker with, so he was happy to finally get his hands on a neat specimen listed on eBay. He wrote an interesting blog post detailing his efforts to connect this old beast to a modern TV.

The main issue with the Aquarius is that it only has an RF video output, which results in a rather poor rendition of its already very limited graphics capabilities. Luckily, there is a fix available in the form of a composite A/V adapter that’s an almost plug-and-play upgrade. The only thing you need to do, as [Leaded Solder] illustrates in his blog post, is open up the computer, desolder the RF modulator and solder the A/V adapter in its place. Getting to that point was a bit tricky due to heavy EMI shields that were fixed in place with lots of solder, requiring liberal use of a desoldering iron. Continue reading “Adding Composite Video To The Mattel Aquarius” →

An array of 2D barcodes stored on a ceramic medium. Each 2D barcode is 25 micrometers wide.

Cerabyte: One Terabyte Per Square Centimeter

September 8, 2023 by Julian Scheffers 45 Comments

Most of us will at one point have run out of storage and either had to buy a larger driver or delete some of those precious files. This problem can happen to data centers, too, with the ever-increasing amount of data stored on servers across the world. [Cerabyte] aims to fix this, with their ceramic-based media promising 1 TB/cm² of areal density.

To put into perspective just how much better this density is, we can compare it against SSDs and hard drives. At the time of writing, the densest SSD (NAND flash storage) is claimed to be 0.1825 TB/cm² and the densest hard drive is claimed to be 0.1705 TB/cm², which means 5.48 times and 5.87 times more dense respectively. The density improvement doesn’t end there — both an SSD and a single HDD platter might be a couple millimeters tall, while a [Cerabyte] layer claims to be merely 50 atoms tall.

[Cerabyte] aims to create 10 PB (10,000 TB) and later 1 EB (1,000,000 TB) racks with their technology, a feat difficult to achieve with mere hard drives. The ceramic-based media is written to using lasers and read from with a microscope, though throughput is limited to a “mere” 1 GB/s, which means filling that one rack could take as long as 110 days. Despite the relatively slow access times, we think this new storage technology is impressive, assuming [Cerabyte] succeeds.

Do you need so much storage that even [Cerabyte] can’t satisfy your needs? Simply use YouTube as infinite storage!