Repairing An HDMI Adapter Doesn’t Go So Well

May 16, 2022 by Al Williams 27 Comments

[Adrian] has a lot of retrocomputers, so he uses an RGB to HDMI converter to drive modern monitors. In particular, he has a box that uses a programmable logic chip to read various RGB signals and ships them to a Raspberry Pi Zero to drive the HDMI output. Sounds great until, of course, something goes wrong.

A converter that had worked stopped working due to a bad board with the programmable logic chip on it. Unlike the retrocomputers, this board has little tiny surface mount components. A little analysis suggested that some of the chip pins were not accepting inputs.

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Striping A Disk Drive The 1970 Way

May 16, 2022 by Al Williams 38 Comments

These days, mass storage for computers is pretty simple. It either uses a rotating disk or else it is solid state. There are a few holdouts using tape, too, but compared to how much there used to be, tape is all but dead. But it wasn’t that long ago that there were many kinds of mass storage. Tapes, disks, drums, punched cards, paper tape, and even stranger things. Perhaps none were quite so strange though as the IBM 2321 Data Cell drive — something IBM internally called MARS.

What is a data cell you might ask? A data cell was a mass storage device from IBM in 1964 that could store about 400 megabytes using magnetic strips that looked something like about a foot of photographic film. The strips resided inside a drum that could rotate. When you needed a record, the drum would rotate the strip you needed to the working part and an automated process would remove the strip in question, wrap it around a read/write head and then put it back when it was done.

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Will MiSTer Fool You Into Learning FPGAs?

May 9, 2022 by Elliot Williams 45 Comments

What’s the killer app for FPGAs? For some people, the allure is the ultra-high data throughput for parallelizable tasks, which can enable some pretty gnarly projects. But what if you’re just starting out? How about 1980s style video games?

The MiSTer FPGA project created a bit of FPGA hardware that makes it easy to build essentially any old school video game or computer platform. That’s a massive clean slate. Of course, you can simply download someone else’s Atari ST or Commodore 64 setup and load it up, but if you want to learn FPGAs while recreating old-school video game machines, you’re going to want to get your hands dirty.

[Mister Retro Wolf] started up a video series last winter (trailer embedded below) where he’s embarked on a project to recreate a classic video game machine from the ground up using the MiSTer FPGA platform. In particular, he’s going to recreate the Namco Tank Battalion arcade game, from the schematics, in Verilog.

This is literally building a 6502-based video game machine from scratch (in gateware), so if you’re interested in retrocomputing or FPGAs, you’ll have something to learn here. He’s gotten through the CPU, screen, tilemap graphics, and memory so far, but it’s not done yet. To follow along, get yourself some hardware and you can probably catch up.

We’ve covered the MiSTer FPGA project before, of course, because we think it’s cool. And if a video game arcade machine is going to be your gateway drug into the seedy world of programmable gates, then so be it.

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Learning Obsolete Technology

May 7, 2022 by Elliot Williams 33 Comments

Tom Nardi and I were talking about his trip to the Vintage Computer Festival on the podcast, and he admitted to not having been a retrocomputer aficionado before his first trip. But he ended up keying some binary machine code into some collection of archaic silicon, and he got it. In the same episode, the sound of the week was a Strowger switch — the old electromechanical “brain” of telephone switching centers of old. The sample I used was from Sam of Look Mum No Computer on YouTube, who got one for his museum and thinks it’s just awesome.

Why do people like this kind of old (obsolete?) tech? It’s certainly not because it’s overwhelmingly capable — the giant old switch is replaced easily by a stack of silicon, and don’t even get me started on the old blinkenlights computer that Tom was keying on. In both of these cases, the people are significantly younger than the tech they’re playing around with, so that rules out nostalgia. What’s left?

I think it’s that sometimes the older technology is more immediate, more understandable, more tangible, and that resonates with people. In a time when we all have wonder devices that can do anything, programmed in languages that are pleasant, using libraries that are nothing short of magical in terms of making difficult things easy, understanding how things work down to the ground is a rare commodity.

But it’s a strange position to find ourselves in, technologically, where there’s almost necessarily a trade-off between the usefulness and functionality of a device with the ability to understand fundamentally how it works.

Paper Tape Reader Self-calibrates, Speaks USB

April 16, 2022 by Donald Papp 22 Comments

Input devices consisting of optical readers for punched paper tape have been around since the earliest days of computing, so why stop now? [Jürgen]’s Paper Tape Reader project connects to any modern computer over USB, acting like a serial communications device. Thanks to the device’s automatic calibration, it works with a variety of paper materials. As for reading speed, it’s pretty much only limited to how fast one can pull tape through without damaging it.

Stacked 1.6 mm PCBs act as an enclosure, of sorts.

While [Jürgen]’s device uses LEDs and phototransistors to detect the presence or absence of punched holes, it doesn’t rely on hardware calibration. Instead, the device takes analog readings of each phototransistor, and uses software-adjusted thresholds to differentiate ones from zeros. This allows it to easily deal with a wide variety of tape types and colors, even working with translucent materials. Reading 500 characters per second isn’t a problem if the device has had a chance to calibrate.

Interested in making your own? The build section of the project has all the design files; it uses only through-hole components, and since the device is constructed from a stack of 1.6 mm thick PCBs, there’s no separate enclosure needed.

Paper tape and readers have a certain charm to them. Cyphercon 4.0 badges featured tape readers, and we’ve even seen the unusual approach of encoding an I²C byte stream directly onto tape.

We’ve Heard Of Bricking A Hard Drive, But…

April 14, 2022 by Al Williams 38 Comments

Mass storage has come a long way since the introduction of the personal computer. [Tech Time Traveller] has an interesting video about the dawn of PC hard drives focusing on a company called MiniScribe. After a promising start, they lost an IBM contract and fell on hard times.

Apparently, the company was faking inventory to the tune of $15 million because executives feared for their jobs if profits weren’t forthcoming. Once they discovered the incorrect inventory, they not only set out to alter the company’s records to match it, but they also broke into an outside auditing firm’s records to change things there, too.

Senior management hatched a plan to charge off the fake inventory in small amounts to escape the notice of investors and government regulators. But to do that, they need to be able to explain where the balance of the nonexistent inventory was. So they leased a warehouse to hold the fraud inventory and filled it with bricks. Real bricks like you use to build a house. Around 26,000 bricks were packaged in boxes, assigned serial numbers, and placed on pallets. Auditors would see the product ready to ship and there were even plans to pretend to ship them to CompuAdd and CalAbco, two customers, who had agreed to accept and return the bricks on paper allowing them to absorb the $15 million write off a little at a time.

Unfortunately, the fictitious excellent financial performance led to an expectation of even better performance in the future which necessitated even further fraud. The company had turned around, but only on paper. A downturn in the computer business and maxed-out credit signaled the beginning of the end. Suppliers and employees weren’t getting paid. A senior manager violated insider trader rules and dumped a lot of stock.

The turnaround CEO finally resigned and a new CEO found the fraud and released the findings that they were in the hole for $100 million. Bankruptcy pushed the company’s assets to Maxtor and criminal charges against 16 people ensued ending in fines and jail time. It isn’t clear if any of the boxed bricks were shipped to anyone by accident or by a disgruntled employee with a rubber paycheck. [Tech Time Traveller] speculates that if someone has one, it would be quite the collector’s item.

We hear about companies doing questionable things, of course, but this really is impressive in scope. At least they weren’t scamming end users as some tech companies have done.

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A Close Look At A Little Known 8-bit Computer

April 8, 2022 by Al Williams 47 Comments

If you read about the history of personal computing, you hear a few familiar names like Microsoft, Apple, and even Commodore. But there were a host of companies that were well known and well regarded back then that are all but forgotten today. Godbout computing, Ohio Scientific, and Southwest Technical Products (SWTP). SWTP is probably best remembered for having a relatively cheap printer and “TV typewriter”, but they also made a 6800-based computer and [Adrian] takes us inside of one.

The 6800 was Motorola’s entry into the microprocessor fray, competing with the Intel 8080. The computer came out scant months after the introduction of the famous Altair 8800. Although the Altair is often credited as being the first hobbyist-grade computer, there were a few earlier ones based on the 8008, but the Altair was the first to be successful.

The SWTP was notable for its day for its blank appearance. Most computers in those days had lots of switches and lights. The SWTP has a blank front with only a power switch and a reset button. A ROM monitor let you use the machine with a terminal. For about the same price as a bare-bones Altair that had no interfaces or memory, you could pick one of these up with most of the extras you would need. The memory was only 2K, but that was 2K more than you got with an Altair at that price point.

The $450 sounds fairly cheap, but in the early 70s, that was a lot of lawns to mow. Of course, while you’d need to add memory to the Altair, you’d have to add some kind of terminal to the SWTP. However, you’d wind up with something more usable but the total bill was probably going to approach $1,000 to get a working system.

Inside the box were some old-fashioned-looking PC boards and connectors that will look familiar to anyone who has been inside 1970s gear. Will it work? We don’t know yet, but we hope it does. [Adrian] promises that will be in the next video.

It is amazing how far we’ve come in less than 50 years. A postage-stamp sized $10 computer now has enough speed and memory to emulate a bunch of these old machines all at once. The SWTP has been on our pages before. A lot of these old machines and companies are all but forgotten, but not by us!

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