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26 Articles

The Bellmac-32 CPU — What?

June 6, 2025 by 32 Comments

If you have never heard of the Bellmac-32, you aren’t alone. But it is a good bet that most, if not all, of the CPUs in your devices today use technology pioneered by this early 32-bit CPU. The chip was honored with the IEEE Milestone award, and [Willie Jones] explains why in a recent post in Spectrum.

The chip dates from the late 1970s. AT&T’s Bell Labs had a virtual monopoly on phones in the United States, but that was changing, and the government was pressing for divestiture. However, regulators finally allowed Bell to enter the computing market. There was only one problem: everyone else had a huge head start.

There was only one thing to do. There was no point in trying to catch the leaders. Bell decided to leap ahead of the pack. In a time when 8-bit processors were the norm and there were nascent 16-bit processors, they produced a 32-bit processor that ran at a — for the time — snappy 2 MHz.

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Unreleased Amiga Hardware Plays MP3s

May 25, 2025 by 33 Comments

The MP3 file type has been around for so long, and is supported by essentially all modern media software and hardware, that it might be surprising to some to learn that it’s actually a proprietary format. Developed in the late 80s and early 90s, it rose to prominence during the Napster/Limewire era of the early 00s and became the de facto standard for digital music, but not all computers in these eras could play this filetype. This includes the Amigas of the early 90s, with one rare exception: this unreleased successor to the A3000 with a DSP chip, which now also has the software to play back these digital tunes.

The AA3000, developed as a prototype by Commodore, was never released to the general public. Unlike the original A3000 this one would have included a digital signal processing chip from AT&T called the DSP3210 which would have greatly enhanced its audio capabilities. A few prototype boards did make it out into the hands of the public, and the retrocomputing scene has used them to develop replicas of these rare machines. [Wrangler] used one to then develop the software needed for the MPEG layer 2 and 3 decoder using this extra hardware, since the original Amiga 3000 was not powerful enough on its own to play these files back.

If you want to follow along with the community still developing for this platform there’s a form post with some more detail for this specific build (although you may need to translate from German). [Wrangler] additionally points out that there are some limitations with this implementation as well, so you likely won’t get Winamp-level performance with this system, but for the Amiga fans out there it’s an excellent expansion of this computer’s capabilities nonetheless.

Thanks to [Andy] for the tip!

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How The Bell System Was Built

July 15, 2024 by 9 Comments

We’ve often thought that while going to the moon in the 1960s was audacious, it was just the flashiest of many audacious feats attempted and accomplished in the 20th century. Imagine, for a minute, that the phone system didn’t exist today, and you stood up in front of a corporate board and said, “Let’s run copper wire to every home and business in the world.” They’d probably send you for a psychiatric evaluation. Yet we did just that, and, in the United States, that copper wire was because of the Bell system, which [Brian Potter] describes in a recent post.

The Bell company, regardless of many name changes and divisions, was clearly a very important company. [Brian] points out that in 1917, it was the second-largest company in the United States and continued to grow, eventually employing a whopping 1% of the entire U.S. workforce. That’s what happens when you have a monopoly on a product that is subject to wild demand. In 1900, Bell handled 5 million calls a day. By 1925, that number was over 50 million. In 1975, it was just shy of 500 million. If Wester Electric — just one part of Bell — was its own company, it would have been the 12th largest company in the U.S. during the 1970s.

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Retrotechtacular: Rebuilding A Fire-Ravaged Telephone Exchange

January 11, 2024 by 15 Comments

Those who haven’t experienced the destruction of a house fire should consider themselves lucky. The speed with which fire can erase a lifetime of work — or a life, for that matter — is stunning. And the disruption a fire causes for survivors, who often escape the blaze with only the clothes on their backs, is almost unfathomable. To face the task of rebuilding a life with just a few smoke-damaged and waterlogged possessions while wearing only pajamas and slippers is a devastating proposition.

As bad as a residential fire may be, though, its impact is mercifully limited to the occupants. Infrastructure fires are another thing entirely; the disruption they cause is often felt far beyond the building or facility involved. The film below documents a perfect example of this: the 1975 New York Telephone Exchange fire, which swept through the company’s central office facility at the corner of 2nd Avenue and 13th Street in Manhattan and cut off service to 300 blocks of the East Village and Lower East Side neighborhoods.

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Retrotechtacular: The Forgotten Vacuum Tube A/D Converters Of 1965

June 8, 2022 by 13 Comments

In any era, the story of electronics has very much been about figuring out how to make something happen with what’s available at the time. And as is often the case, the most interesting developments come from occasions when needs exceed what’s available. That’s when real innovation takes place, even if circumstances conspire to keep the innovation from ever taking hold in the marketplace.

This gem of a video from the Antique Wireless Association has a perfect example of this: the long-lost analog-to-digital converter vacuum tube. Like almost every mid-20th-century innovation in electronics, this one traces its roots back to the Bell Laboratories, which was keenly interested in improving bandwidth on its massive network of copper lines and microwave links. As early as 1947, one Dr. Frank Gray, a physicist at Bell Labs, had been working on a vacuum tube that could directly convert an analog signal into a digital representation. His solution was a cathode ray tube similar to the CRT in an oscilloscope. A beam of electrons would shine down the length of the tube onto a shadow mask containing holes arranged in a “reflected binary code,” which would later be known as a Gray code. The analog signal to be digitized was applied to a pair of vertical deflector plates, which moved the beam into a position along the plate corresponding to the voltage. A pair of horizontal deflector plates would then scan the beam across the shadow mask; where electrons fell on a hole, they would pass through to an output plate to be registered as a bit to be set.

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Inspecting a SIM card via MTM

Diving The Depths Of Ma Bell

December 27, 2021 by 13 Comments

The modern smartphone is a marvel of sensors, radios, inputs, outputs, and processing power. In particular, some of those radios, such as WiFi and cellular, have grown fiendishly complex over the years. Even when that complexity is compressed down for the user into the one-dimensional space of the signal strength bars at the top of your phone. So when [David Burgess] was asked to look at some cellphone records of text messages and figure out where some of the more mysterious messages were coming from, it led him down a rabbit hole into the dark arts behind the glowing phone screen.

The number in question was 1111340002, sent by a phone connected to AT&T at the time, and was crucial for a legal case around distracted driving. [David’s] tools in his investigation were YateBTS (a cellular network simulator), SimTrace2 (pictured above), and old reliable Wireshark. Since the number isn’t a specific phone number and is not reachable from the public phone network, it must be a unique number inside AT&T processed by one particular AT&T SMSC (Short Message service center). The SMSC in question is in Atlanta and isn’t a typical texting center, so it must have some particular purpose. The message’s payload is raw binary rather than text, and [David] has done a pretty good job of decoding the majority of the format.

The most exciting revelation in this journey is that the phone (in the traditional sense) does not send this message. The processor on the phone does not know this message and executes no code to send it. Instead, the SIM card itself sends it. The SIM card is connected directly to the baseband processor on the phone, and the baseband polls the sim every so often, asking for any commands. One of those commands is an SMS (though many other commands have worrying consequences).

The SMS that [David] was chasing is triggered whenever a SIM detects a new IMEI, and the message lets the network know what about the previous and current IMEI. However, in the case of this message, it was unlikely that the SIM changed phones, so what happened? After some additional lab work and the deposition of an AT&T employee, [David] showed that a baseband firmware update would also trigger this SMS.

It’s a fascinating journey into the fragmented world of a smartphone’s minds and [David] does a fantastic job on the writeup. If you’re interested in sniffing wireless accessories, you will enjoy this soundbar’s wireless protocol laid bare.

The Modular Connector And How It Got That Way

October 2, 2018 by 70 Comments

They adorn the ends of Cat5 network patch cables and the flat satin cables that come with all-in-one printers that we generally either toss in the scrap bin or throw away altogether. The blocky rectangular plugs, molded of clear plastic and holding gold-plated contacts, are known broadly as modular connectors. They and their socket counterparts have become ubiquitous components of the connected world over the last half-century or so, and unsurprisingly they had their start where so many other innovations began: from the need to manage the growth of the telephone network and reduce costs. Here’s how the modular connector got that way.

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