Continuing his reverse-engineering of the Intel 8087, [Ken Shirriff] covers the conditional tests that are implemented in the microcode of this floating point processing unit (FPU). This microcode contains the details on how to perform the many types of specialized instructions, like cos and arctan, all of which decode into many microcode ops. These micro ops are executed by the microcode engine, which [Ken] will cover in more detail in an upcoming article, but which is effectively its own CPU.

Conditional instructions are implemented in hardware, integrating the states of various functional blocks across the die, ranging from the instruction decoder to a register. Here, the evaluation is performed as close as possible to the source of said parameter to save on wiring.

Implementing this circuitry are multiplexers, with an example shown in the top die shot image. Depending on the local conditions, any of four pass transistors is energized, passing through that input. Not shown in the die shot image are the inverters or buffers that are required with the use of pass transistors to amplify the signal, since pass transistors do not provide that feature.

Despite how firmly obsolete the 8087 is today, it still provides an amazing learning opportunity for anyone interested in ASIC design, which is why it’s so great that [Ken] and his fellow reverse-engineering enthusiasts keep plugging away at recovering all this knowledge.

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[Ronan] likes 35mm film photography, but the world, of course, has gone digital. He picked up an Epson FilmScan 200 for about €10. This wonder device from 1997 promised to convert 35mm film to digital at 1200 DPI resolution. But there was a catch: it connects via SCSI. Worse, the drivers were forever locked to Windows 95/98 and Mac System 7/8.

In a surprise twist, though, [Ronan] recently resurrected a Mac SE/30 with the requisite SCSI port and the System 7 OS. Problem solved? Not quite. The official software is a plugin for Photoshop. So the obvious answer is to write new software to interact with the device.

First, of course, you have to figure out how the device works. A service manual provided clues that, as far as the SCSI bus knew, the device wasn’t a scanner at all, but a processor. The processor, though, used SCSI as a simple pipe to handle Epson’s standard “ESC/I” protocol.

Armed with that information and a knowledge of the Mac’s SCSI Manager API, the rest is just coding. Well, that is until [Ronan] tried to scan the other five negatives in the six-negative film carrier. He was frustrated until he found an old patched SANE driver for the scanner from 2002. By looking at how it worked, he was able to figure out how to switch to the other negatives.

Color scanning also took a little coaxing. The scanner returns three monochrome images, one for each color channel. Some assembly, then, is required. In the end, though, the project was a complete success. Can’t find a FilmScan 200? Don’t have a SCSI port? There’s always the roll-your-own approach.

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Emulating older computers on microcontrollers has been a staple of retrocomputing for many years now, with most 8-bit and some 16-bit machines available on Atmel, ARM, or ESP32 platforms. But there’s always been a horsepower limit, a point beyond which a microcontroller is no longer enough, and a “proper” computer is needed. One of those barriers now appears to have been broken, as microcontroller-based emulation moves into the 32-bit era. [Amcchord] has the Basilisk II emulator ported to the ESP32-P4 platform, providing a 68040 Mac able to run OS8.1. This early-1990s-spec machine might not seem like much in 2026, but it represents a major step forward.

The hardware it uses is the M5Stack Tab5, and it provides an emulated Mac with up to 16 MB of memory. Remember, in 1992 this would have been a high-spec machine. It manages a 15 frames per second refresh rate, which is adequate for productivity applications. The emulator uses the Tab5’s touchscreen to emulate the Mac mouse alongside support for USB input devices. To 1990 hackers, it’s almost the Mac tablet you didn’t know you would want in the future.

We like this project, both because it’s advancing the art of emulation on microcontrollers, and also because it delivers a computer that’s useful for some of the things you might have done with a Mac in 1992 and could even do today. Pulling this out on the train back then would have blown people’s minds. There’s even a chance that MacOS on something like this would turn a few heads in 2026. It’s certainly not the first emulated Mac we’ve seen though.

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The Tamagotchi Connection is a series of Tamagotchi toys that took the original portable pet concept and mixed things up with a wireless connection, which allowed you to interact with the pets of other proud Tamagotchi owners. This wireless connection is implemented using an infrared transceiver, somewhat like IrDA, but as [Zach Resmer] discovered while reverse-engineering this connection, it’s actually what is called ‘Nearly NEC’ by [Natalie Silvanovich], who has a GitHub repository full of related Tamagotchi hacking tools and ROM dumps.

With the protocol figured out, creating a transceiver for low-bitrate infrared communication isn’t particularly hard. In this case, it was implemented using an RP2040 MCU and an appropriate IR LED and receiver pair. This Tamagometer project was also implemented as an app for the Flipper Zero, and a custom PCB called the Pico TamaBadge by [Daniel Weidman].

There’s a web application associated with [Zach]’s project using a Web Serial-enabled browser (i.e. Chrome). The serial protocol is somewhat documented in the patent for the device’s connection feature, which makes it relatively easy to implement yourself.

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While EEG research might help you figure out extrasensory perception, we won’t be betting on it. However, if you want to read EEG data and use an ESP32, [Cerelog-ESP-EEG] might be the right project for you. The commercial project is an 8-channel biosensing board suitable for EEG, EMG, ECG, and brain-computer interface studies. However, the company says, “We love the hacker community! We explicitly grant permission for Personal & Educational Use.” We love you too.

They do require you to agree not to sell boards you are building, and they give you schematics, but no PC board layout. That’s understandable, although we’d guess that achieving good results will require understanding how to lay out highly sensitive circuits.

What you do get is the schematic and the firmware source. They note that you may have to modify the firmware if you want to switch modes, change gain, or enable haptic feedback, among other things. At the application layer, the device is compatible with Lab Streaming Layer, and there is a fork of OpenBCI (brain control interface) that understands how to talk to the board.

Even if you don’t want to directly clone the device, there’s a ton of information here if you are interested in EEG or any other small signal acquisition. We’ve seen a number of interfaces like this, but we are still waiting to see a killer application.

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A Vector Network Analyser, or VNA, is the ultimate multi-tool of RF test equipment. They can now be had in not very capable form for almost pocket money prices, but the professional-grade ones cost eye-watering sums. Enough to make an older VNA for a few hundred on eBay a steal, and [W3AXL] has just such a device in an HP 8714C. It’s the height of 1990s tech with a floppy drive and a green-screen CRT, but he’s homing right in on the VGA monitor port on the back. Time for a colour LCD upgrade!

There are two videos below the break, posted a year apart, because as we’re sure many of you will know, events have a habit of getting in the way of projects. In the first, we see the removal of the CRT module and safe extraction of its electronics, followed by the crafting of a display bezel for the LCD. Meanwhile, the second video deals with the VNA itself, extracting the VGA signal and routing it forward to the new module.

We’re struck not for the first time by the high quality of the construction in this piece of test equipment; it’s not only substantial but well designed for maintenance and disassembly. [W3AXL] sensibly leaves the RF part alone, but both CRT and mainboard modules slide out with minimal screw removals and few problems in reassembly.

He goes the extra mile with a second iteration of the display mount and a curved print to fit the CRT shape in the front panel. The result is a colour display on the instrument, and we’re guessing, a much lighter device, too.

If VNAs are new to you, then you might wish to learn a little about them,

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A knob can make a surprisingly versatile interface, particularly if it’s the SmartKnob, which builds a knob around a BLDC motor for programmable haptic response. It can rotate freely or with a set resistance, spring back to a fixed point when released, stick at detent points, and completely change its behavior as the interface demands. For people inexperienced in electronic assembly, though, smartknobs can be difficult to assemble. That’s why [Kokensha Tech] designed a simpler version, while at the same time letting it use a wider range of BLDC motors.

In addition to a motor, the original design used a magnetic encoder to detect position and a strain gauge to detect pressure on the knob. A circular LCD on the knob itself provided visual feedback, but it also required the motor to have a hollow center shaft. The LCD control wires running through the shaft proved tricky to assemble. [Kokensha Tech] moved the display out of the knob and onto a separate breakout board, which plugs into the controller board. This greatly broadens the range of compatible motors, since they no longer need a hollow shaft.

The motor now fits on a separate carrier board, which makes it easier to swap out different motors. The carrier board has mounting holes sized for a wide variety of motors, and four different types of motor connectors. [Kokensha Tech] also redesigned the rest of the PCB for easier soldering, while avoiding components with narrow pin spacing whenever possible. The original design used a LILYGO T-micro32 Plus MCU. The ESP32 is both cheaper and easier to solder, so it was a no-brainer to swap it in.

We’ve covered the original SmartKnob before, including a more in-depth look at its design. We’ve also seen another project use BLDCs and field-oriented control to make haptic knobs.

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