How DEC’s LANBridge 100 Gave Ethernet A Fighting Chance

April 9, 2024 by Maya Posch 17 Comments

Alan Kirby (left) and Mark Kempf with the LANBridge 100, serial number 0001. (Credit: Alan Kirby)

When Ethernet was originally envisioned, it would use a common, shared medium (the ‘Ether’ part), with transmitting and collision resolution handled by the carrier sense multiple access with collision detection (CSMA/CD) method. While effective and cheap, this limited Ethernet to a 1.5 km cable run and 10 Mb/s transfer rate. As [Alan Kirby] worked at Digital Equipment Corp. (DEC) in the 1980s and 1990s, he saw how competing network technologies including Fiber Distributed Data Interface (FDDI) – that DEC also worked on – threatened to extinguish Ethernet despite these alternatives being more expensive. The solution here would be store-and-forward switching, [Alan] figured.

After teaming up with Mark Kempf, both engineers managed to convince DEC management to give them a chance to develop such a switch for Ethernet, which turned into the LANBridge 100. As a so-called ‘learning bridge’, it operated on Layer 2 of the network stack, learning the MAC addresses of the connected systems and forwarding only those packets that were relevant for the other network. This instantly prevented collisions between thus connected networks, allowed for long (fiber) runs between bridges and would be the beginning of the transformation of Ethernet as a shared medium (like WiFi today) into a star topology network, with each connected system getting its very own Ethernet cable to a dedicated switch port.

On the left, the main board of the dual board computer, with the CPU and a bunch of connectors visible. On the right, the addon board is shown, with all the extra connectors as described in the article

A Nifty F1C100S Dual-Board Computer

April 2, 2024 by Arya Voronova 15 Comments

The F1C100S (and the F1C200S) is a super simple CPU to use – it’s QFN, it has RAM built-in, and it can run Linux. It just makes sense that we bring it up to you once again, this time, on this dual-board computer by [minilogic]. The boards look super accessible to build for a Linux computer, and it’s alright if you assemble only one of them, too – the second board just makes this computer all that much nicer to use!

One the main board, you get the CPU itself, a couple USB ports, headphone and mic jacks, a microphone, a microSD socket, power management, SPI flash chip, plus some buttons, headers and USB-UART for debug. Add the second board, however, and you get a HDMI video output socket, a RGBTTL LCD header, LiIon battery support, RTC, and even FM radio with TV input.

One problem with this computer – it’s not open-source in the way that we expect and respect, as there’s no board files to be seen. However, at least the schematics are public, so it shouldn’t be hard, and the author provides quite a bit of example code for the F1C100S, which softens the blow. Until the design files are properly published, we can at least learn from the idea and the schematics. If you like what the F1C100S CPU offers, there are other projects you can take things from too, like this low-cost handheld we’re patiently waiting for, or this Linux-powered business card.

Video Poker Takes Your Money In 10 Lines Of BASIC

March 21, 2024 by Donald Papp 14 Comments

It wasn’t easy, but [D. Scott Williamson] succeeded in implementing Jacks or Better Video Poker in 10 lines of BASIC, complete with flashing light and sound! Each round, one places a bet then plays a hand of 5-card draw, hoping to end up with Jacks or better.

This program is [Scott]’s entry into the 2024 BASIC 10 Liner Contest, which at this writing has concluded submissions and expects to announce results on April 6th 2024. Contestants may choose any 8-bit computer system BASIC, and must implement their program within ten lines of code (classically limited to 80 characters per line, but there are different categories with different constraints on line width.)

10 lines of BASIC is truly an exercise in information density.

We’ve seen impressive 10-line BASIC programs before, like this re-implementation of the E.T. video game. (Fun fact: while considered one of the worst video games of all time, there’s a compelling case to be made that while it was a flop, it was ahead of its time and mostly just misunderstood.)

These programs don’t look much like the typical BASIC programs many of us remember. They are exercises in information density, where every character counts. So we’re delighted to see [Scott] also provides a version of his code formatted and commented for better readability, and a logical overview that steps through each line.

He spends a little time talking about the various challenges, as well. For example, hand ranking required a clever solution. IF…THEN conditionals would rapidly consume the limited lines of code, so hands are ranked programmatically. The 52-card deck is also simulated, rather than simply generating random cards on the fly.

The result looks great, and you can watch it in action in the video, just under the page break. If this sort of challenge tweaks your interest, there’s plenty of time to get started on next year’s BASIC 10 Liner Contest. Fire up those emulators!

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These Keycaps Are 100% Recycled Plastic

March 20, 2024 by Kristina Panos 4 Comments

Artisan keycaps are generally meant to replace your Escape key, though they can be used anywhere you like (as long as they fit, of course). Keycap maker [tellybelly] of jankycaps has been experimenting with making keycaps out of 100% recycled plastic, and offers an interesting post detailing their development and production process.

What do you do when normal injection molding tooling is out of your budget, and silicone molds simply won’t do? You turn to 3D printing if you can. In this case, [tellybelly] and company found a resin designed to withstand high temperatures.

[tellybelly] was able to design the mold using a plethora of online resources, and even verified the flow using a special program. Although the first two versions worked, they had some flaws. Third time’s the charm, though, and then it was time to sort plastic and fire up the shredder.

After heating up the shreds to 200 °C or so, it was time to start the injecting. This part isn’t exactly a cakewalk — mixing different plastics together can vary the workable temperature range that doesn’t degrade the plastic. Although it sounds like the end, [tellybelly] reports that they spent just as much time here as they did at the drawing board, experimenting with pressure on the mold, various cool-down methods, and how long to wait before opening the mold.

Via reddit

PDP-10 Fits In Your Living Room

March 13, 2024 by Al Williams 8 Comments

[Oscar] at Obsolescence Guaranteed is well-known for fun replicas of the PDP-8 and PDP-11 using the Raspberry Pi (along with some other simulated vintage computers). His latest attempt is the PDP-10, and you can see how it looks in the demo video below.

Watching the video will remind you of every old movie or TV show you’ve ever seen with a computer, complete with typing noise. The PDP-10, also known as a DECsystem-10, was a mainframe computer that usually ran TOPS-10. These were technically “mainframes” in 1966, although the VAX eclipsed the system. By 1983 (the end of the PDP-10’s run), around 1,500 had been sold, including ones that ran at Harvard, Stanford, Carnegie Mellon, and — of course — MIT. They also found homes at CompuServe and Tymshare.

The original 36-bit machine used transistors and was relatively slow. By the 1970s, newer variants used ICs or ECL and gained some speed. A cheap version using the AM2901 bit-slice CPU and a familiar 8080 controlling the system showed up in 1978 and billed itself as “the world’s lowest cost mainframe.”

The Knight terminals were very unusual for the day. They each used a PDP-11 and had impressive graphics capability compared to similar devices from the early 1970s. You can see some of that in the demo video.

Naturally, anyone who used a PDP-10 would think a Raspberry Pi was a supercomputer, and they wouldn’t be wrong. Still, these machines were the launching pad for Adventure, Zork, and Altair Basic, which spawned Microsoft.

The cheap version of these used bitslice which we’ve been talking about lately. [Oscar] is also known for the KIMUno, which we converted into a COSMAC Elf.

Hackaday Links: March 10, 2024

March 10, 2024 by Dan Maloney 17 Comments

We all know that we’re living in a surveillance state that would make Orwell himself shake his head, but it looks like at least one company in this space has gone a little rogue. According to reports, AI surveillance start-up Flock <<insert gratuitous “What the Flock?” joke here>> has installed at least 200 of its car-tracking cameras on public roads in South Carolina alone. That’s a serious whoopsie, especially since it’s illegal to install anything on state infrastructure without permission, which it appears Flock failed to obtain. South Carolina authorities are making a good show of being outraged about this, but it sort of rings hollow to us, especially since Flock now claims that 70% of the population (of the USA, we presume) is covered by their technology. Also, police departments across the country are in love with Flock’s service, which lets them accurately track the movements of potential suspects, which of course is everyone. No word on whether Flock will have to remove the rogue cameras, but we’re not holding our breath.

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Doubling The CPU Speed Of The TRS-80 Model 100 With A Mod Board

February 18, 2024 by Maya Posch 13 Comments

The TRS-80 Model 100 was released in 1983, featuring an 80C85 CPU that can run at 5 MHz, but only runs at a hair under 2.5 MHz, due to 1:2 divider on the input clock. Why cut the speed in half? It has a lot to do with the focus of the M100 on being a portable device with low power usage. Since the CPU can run at 5 MHz and modding these old systems is a thing, we got a ready-made solution for the TRS-80 M100, as demonstrated by [Ken] in a recent video using one of his ‘daily driver’ M100s.

This uses the board design from the [Bitchin100] website, along with the M100 ROM image, as one does not simply increase the CPU clock on these old CPUs. The issue is namely that along with the CPU clock, connected components on the CPU bus now have to also run at those speeds, and deal with much faster access speed requirements. This is why beyond the mod board that piggybacks on top of the MPU package, it’s also necessary to replace the system ROM chip (600 ns) with a much faster one, like the Atmel AT27C256R (45 ns), which of course requires another carrier board to deal with incompatible pinouts.

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