The Microtronic Phoenix Computer System

September 15, 2025 by John Elliot V 4 Comments

A team of hackers, [Jason T. Jacques], [Decle], and [Michael A. Wessel], have collaborated to deliver the Microtronic Phoenix Computer System.

In 1981 the Busch 2090 Microtronic Computer System was released. It had a 4-bit Texas Instruments TMS1600 microcontroller, ran at 500 kHz, and had 576 bytes of RAM and 4,096 bytes of ROM. The Microtronic Phoenix computer system is a Microtronic emulator. It can run the original firmware from 1981.

Between them the team members developed the firmware ROM dumping technology, created a TMS1xxx disassembler and emulator, prototyped the hardware, developed an Arduino-based re-implementation of the Microtronic, designed the PCB, and integrated the software.

Unlike previous hardware emulators, the Phoenix emulator is the first emulator that is not only a re-implementation of the Microtronic, but actually runs the original TMS1600 firmware. This wasn’t possible until the team could successfully dump the original ROM, an activity that proved challenging, but they got there in the end! If you’re interested in the gory technical details those are here: Disassembling the Microtronic 2090, and here: Microtronic Firmware ROM Archaeology. Continue reading “The Microtronic Phoenix Computer System” →

Retro X86 With 486Tang

September 14, 2025 by Al Williams 4 Comments

Tang FPGA boards are affordable, and [nand2mario] has been trying to get an x86 core running on one for a while. Looks like it finally worked out, as there is an early version of the ao486 design on a Tang FPGA board using a Gowin device. That core’s available on the MiSTer platform, which emulates games using an Altera Cyclone device.

Of course, porting something substantial between FPGA architectures is not trivial. In addition, [nand2mario] made some changes. The original core uses DDR3 memory, but for the Tang and the 486, SDRAM makes more sense. The only problem is that the Tang’s SDRAM is 16 bits wide, which would imply you need two cycles per 32-bit access. To mitigate this, the memory system runs at twice the main clock frequency. Of course, that’s kind of double data rate, but not in the same way as DDR memory.

Continue reading “Retro X86 With 486Tang” →

How The TI-99/4A Home Computer Worked

September 11, 2025 by John Elliot V 56 Comments

Over on YouTube [The 8-Bit Guy] shows us how the TI-99/4A home computer worked.

[The 8-Bit Guy] runs us through this odd 16-bit home computer from back in the 1980s, starting with a mention of the mysterious extra “space” key on its antiquated keyboard. The port on the side is for two joysticks which share a bus, but you can find boards for compatibility with “newer” hardware, particularly the Atari-style joysticks which are easier to find. The AV port on the back is an old 5-pin DIN such as was typical from Commodore and Atari at the time (also there is a headphone port on the front). The other DB9 port on the back of the device is the port for the cassette interface.

The main cartridge interface is on the front right of the machine, and there’s a smaller expansion socket on the right hand side. The front interface is for loading software (on cartridges) and the side interface is for peripherals. The system boots to a now famous “press any key” prompt. (We know what you’re thinking: “where’s the any key!?” Thanks Homer.)

Continue reading “How The TI-99/4A Home Computer Worked” →

Scott holding the demo board which has a 7-segment display and keyboard attached

4-bit Single Board Computer Based On The Intel 4004 Microprocessor

September 11, 2025 by John Elliot V 8 Comments

[Scott Baker] is at it again and this time he has built a 4-bit single board computer based on the Intel 4004 microprocessor.

In the board design [Scott] covers the CPU (both the Intel 4004 and 4040 are supported), and its support chips: the 4201A clock-generator, its crystal, and the 4289 Standard Memory Interface. The 4289 irons out the 4-bit interface for use with 8-bit ROMs. Included is a ATF22V10 PLD for miscellaneous logic, a 74HCT138 for chip-select, and a bunch of inverters for TTL compatibility (the 4004 itself uses 15 V logic with +5 V Vss and -10 V Vdd).

[Scott] goes on to discuss the power supply, ROM and page mapper, the serial interface, the RC2014 bus interface, RAM, and the multimodule interface. Then comes the implementation, a very tidy custom PCB populated with a bunch of integrated circuits, some passive components, a handful of LEDs, and a few I/O ports. [Scott] credits Jim Loo’s Intel 4004 SBC project as the genesis of his own build.

If you’re interested in seeing this board put to work check out the video embedded below. If you’d like to know more about the 4004 be sure to check out Supersize Your Intel 4004 By Over 10 Times, The 4004 Upgrade You’ve Been Waiting For, and Calculating Pi On The 4004 CPU, Intel’s First Microprocessor.

Continue reading “4-bit Single Board Computer Based On The Intel 4004 Microprocessor” →

65F02 Is An FPGA 6502 With A Need For Speed

September 10, 2025 by Tyler August 8 Comments

Does the in 65F02 “F” stand for “fast” or “FPGA”? [Jurgen] doesn’t know, but his drop-in replacement board for the 6502 and 65c02 is out there and open source, whatever you want it to stand for.

The “f” could easily be both, since at 100 MHz, the 65f02 is blazing fast by 6502 standards–literally 100 times the speed of the first chips from MOS. That speed comes from the use of a Spartan 6 FPGA core to implement the 6502 logic; making the “f” stand for “FPGA” makes sense, given that the CMOS version of the chip was dubbed the 65c02. The 65f02 is a tiny PCB containing the FPGA and all associated hardware that shares the footprint of a DIP-40 package, making it a drop-in replacement. A really fast drop-in replacement.

You might be thinking that that’s insane, and that (for example) the memory on an Apple ][ could never run at 100 MHz and so you won’t get the gains. This is both true, and accounted for: the 65F02 has an internal RAM “cache” that it mirrors to external memory at a rate the bus can handle. When memory addresses known to interact with peripherals change, the 65f02 slows down to match for “real time” operations.

The USB adapter board for programming is a great touch.

Because of this the memory map of the external machine matters; [Jurgen] has tested the Commodore PET and Apple ][, along with a plethora of German chess computers, but, alas, this chip is not currently compatible with the Commodore 64, Atari 400/800 or BBC Micro (or at least not tested). The project is open source, however, so you might be able to help [Jurgen] change that.

We admit this project isn’t totally new– indeed, it looks like [Jurgen]’s last update was in 2024– but a fast 6502 is just as obsolete today as it was when [Jurgen] started work in 2020. That’s why when [Stephen Walters] sent us the tip (via electronics-lab), we just had to cover it, especially considering the 6502’s golden jubilee.

We also recently featured a 32-bit version of the venerable chip that may be of interest, also on FPGA.

Rackintosh Plus Is The Form Factor Nobody Has Been Waiting For

September 10, 2025 by Tyler August 20 Comments

For all its friendly countenance and award-winning industrial design, there’s one thing the venerable Macintosh Plus can’t do: fit into a 1U rack space. OK, if we’re being honest with ourselves, there are a lot of things a Mac from 1986 can’t do, but the rack space is what [identity4] was focused on when they built the 2025 Rackintosh Plus.

Some folks may have been fooled by this ad to think this was an actual product.

For those of you already sharpening your pitchforks, worry not: [identity4]’s beloved vintage Mac was not disassembled for this project. This rack mount has instead become the home for a spare logic board they had acquired Why? They wanted to use a classic Mac in their studio, and for any more equipment to fit the space, it needed to go into the existing racks. It’s more practical than the motivation we see for a lot of hacks; it’s almost surprising it hasn’t happened before. (We’ve seen Mac Minis in racks, but not the classic hardware.)

Aside from the genuine Apple logic board, the thin rack also contains a BlueSCSI hard drive emulator, a Floppy Emu for SD-card floppy emulator, an RGB-to-HDMI converter to allow System 7 to shine on modern monitors, and of course a Mean Well power supply to keep everything running.The Floppy Emu required a little light surgery to move the screen so it would fit inside the low-profile rack. [identity4] also broke out the keyboard and mouse connectors to the front of the rack, but all other connectors stayed on the logic board at the rear.

Sound is handled by a single 8-ohm speaker that lives inside the rack mount, because even if the Rackintosh can now fit into a 1U space, it still can’t do stereo sound…or anything else a Macintosh Plus with 4 MB of RAM couldn’t do. Still, it’s a lovely hack. and the vintage-style advertisement was an excellent touch.

Now they just need the right monochrome display.

Was Action! The Best 8-Bit Language?

September 9, 2025 by Tyler August 22 Comments

Most people’s memories of programming in the 8-bit era revolve around BASIC, and not without reason. Most of the time, it was all we had. On the other hand, there were other options if you sought them out, and [Paul Lefebvre] makes the case that Goto10Retro that Action! was the best of them.

The limits of BASIC as an interpreted language are well-enough known that we needn’t go over them here. C and Pascal were available for some home computers in the 1980s, and programs written in those languages ran well, but compiling them? That was by no means guaranteed.

The text editor. Unusual for Atari at the time, it allowed scrolling along a line of greater than 40 char.

For those who lived on the Atari side of the fence, the Action! language provided a powerful alternative. Released by Optimized Systems Software in 1983, Action! was heavily optimized for the 6502, to the point that compiling and running simple programs with “C” and “R” felt “hardly slower” than typing RUN in BASIC. That’s what [Paul] writes, anyway, but it’s a claim that almost has to be seen to be believed.

You didn’t just get a compiler for your money when you bought Action!, though. The cartridge came with a capable text editor, simple shell, and even a primitive debugger. (Plus, of course, a hefty manual.) It’s the closest thing you’d find to an IDE on a computer of that class in that era, and it all fit on a 16 kB cartridge. There was apparently also a disk release, since the disk image is available online.

Unfortunately for those of us in Camp Commodore, the planned C-64 port never materialized, so we missed out on this language. Luckily our 64-bit supercomputers can easily emulate Atari 8-bit hardware and we can see what all the fuss was about. Heck, even our microcontrollers can do it.