#vintagecomputers

🎄💾🗓️ Day 4: Retrocomputing Advent Calendar - The DEC PDP-11! 🎄💾🗓️

Released by Digital Equipment Corporation in 1970, the PDP-11 was a 16-bit minicomputer known for its orthogonal instruction set, allowing flexible and efficient programming. It introduced a Unibus architecture, which streamlined data communication and helped revolutionize computer design, making hardware design more modular and scalable. The PDP-11 was important in developing operating systems, including the early versions of UNIX. The PDP-11 was the hardware foundation for developing the C programming language and early UNIX systems. It supported multiple operating systems like RT-11, RSX-11, and UNIX, which directly shaped modern OS design principles. With over 600,000 units sold, the PDP-11 is celebrated as one of its era's most versatile and influential "minicomputers".

Check out the wikipedia page for some great history, photos (pictured here), and more -

And here's a story from Adafruit team member, Bill!

The DEC PDP-11 was the one of the first computers I ever programmed. That program was 'written' with a soldering iron.

I was an art student at the time, but spending most of my time in the engineering labs. There was a PDP-11-34 in the automation lab connected to an X-ray spectroscopy machine. Starting up the machine required toggling in a bootstrap loader via the front panel. This was a tedious process. So we ordered a diode-array boot ROM which had enough space to program 32 sixteen bit instructions.

Each instruction in the boot sequence needed to be broken down into binary (very straightforward with the PDP-11 instruction set). For each binary '1', a diode needed to be soldered into the array. The space was left empty for each '0'. 32 sixteen bit instructions was more than sufficient to load a secondary bootstrap from the floppy disk to launch the RT-11 operating system. So now it was possible to boot the system with just the push of a button.

I worked with a number DEC PDP-11/LSI-11 systems over the years. I still keep an LSI-11-23 system around for sentimental reasons.

Sinclair ZX Spectrum 128K

In 1985, Sinclair Research unveiled what would become the last and most powerful member of the legendary Spectrum family — the ZX Spectrum 128K.

After the enormous success of the ZX Spectrum 48K, which had defined home computing in the UK and Europe, Sinclair aimed to take the next step: to make the Spectrum not just a gaming machine, but a truly capable home computer for both entertainment and productivity.

Codenamed “Derby”, the 128K was originally developed for the Spanish market (through Sinclair’s local partner Investrónica), before launching in the UK in early 1986.

A leap in capability

At its heart was the same Zilog Z80A processor running at 3.5 MHz, but now backed by 128 kilobytes of RAM — a massive jump that allowed for larger, more ambitious software.

The machine introduced:

The AY-3-8912 sound chip, delivering rich 3-channel music.

Two memory banks, switchable between 48K and 128K modes, for full compatibility with older games.

A redesigned 128 BASIC interpreter with a built-in menu system and on-screen editor.

RS-232, allowing advanced users to connect printers.

Legacy

Although the 128K arrived just as the 8-bit era was beginning to fade, it marked the end of an era with style. It was the last Spectrum designed by Sir Clive Sinclair’s original team, before Amstrad acquired the brand and released the +2 and +3 models (with built-in cassette and floppy drives).

Even today, nearly 40 years later, the Spectrum 128K remains a symbol of British ingenuity: affordable, creative, and full of charm. For millions of Europeans, it wasn’t just a computer — it was their first window into programming, gaming, and digital imagination.

🎄💾🗓️ Day 8: Retrocomputing Advent Calendar - Commodore PET 🎄💾🗓️

The Commodore PET (Personal Electronic Transactor) came out in 1977 and was among the earliest personal computers - featuring an all-in-one design with a keyboard, monochrome monitor, and cassette deck - all within a single chassis. Powered by an MOS Technology 6502 microprocessor running at 1 MHz, it had 4 KB of RAM and was expandable up to 96 KB in later models. The PET had Commodore BASIC stored in ROM, allowing users to write and execute programs directly. Its display supported text resolutions of 40×25 or 80×25 characters, using the PETSCII character set for semigraphic capabilities. While early models did not have sound, later versions included a basic beeper. PET's all-in-one design and user-friendly interface contributed to its popularity in education and business, and it sold approximately 219,000 units before its discontinuation in 1982.

Check out the wikipedia page for some extended history and great photos -

🎄💾🗓️ Day 9: Retrocomputing Advent Calendar - The Apple Lisa 🎄💾🗓️

The Apple Lisa, introduced on January 19, 1983, was a pioneering personal computer notable for its graphical user interface (GUI) and mouse input, a big departure from text-based command-line interfaces. Featured a Motorola 68000 CPU running at 5 MHz, 1 MB of RAM (expandable to 2 MB), and a 12-inch monochrome display with a resolution of 720×364 pixels. The system initially included dual 5.25-inch "Twiggy" floppy drives, later replaced by a single 3.5-inch Sony floppy drive in the Lisa 2 model. An optional 5 or 10 MB external ProFile hard drive provided more storage.

The Lisa's price of $9,995 (equivalent to approximately $30,600 in 2023) and performance issues held back its commercial success; sales were estimated at about 10,000 units.

It introduced advanced concepts such as memory protection and a document-oriented workflow, which influenced future Apple products and personal computing.

The Lisa's legacy had a huge impact on Apple computers, specifically the Macintosh line, which adopted and refined many of its features. While the Lisa was not exactly a commercial success, its contributions to the evolution of user-friendly computing interfaces are widely recognized in computing history.

These screen pictures come from Adafruit fan Philip " It still boots up from the Twiggy hard drive and runs. It also has a complete Pascal Development System." …"mine is a Lisa 2 with the 3.5” floppy and the 5 MB hard disk. In addition all of the unsold Lisa machines reached an ignominious end."

What end was that? From the Verge -

In September 1989, according to a news article, Apple buried about 2,700 unsold Lisa computers in Logan, Utah at a very closely guarded garbage dump. The Lisa was released in 1983, and it was Apple’s first stab at a truly modern, graphically driven computer: it had a mouse, windows, icons, menus, and other things we’ve all come to expect from “user-friendly” desktops. It had those features a full year before the release of the Macintosh.

Article, and video…

Check out the Apple Lisa page on Wikipedia

, the Computer History's article -

and the National Museum of American History – Behring center -

🎄💾🗓️ Day 15: Retrocomputing Advent Calendar - BBC Micro🎄💾🗓️⌨️🇬🇧

The BBC Micro was an 8-bit microcomputer introduced in 1981 by Acorn Computers under the BBC Computer Literacy Project of the UK, launched with a 6502A processor running at 2 MHz, supported 16 KB to 32 KB of RAM, and featuring a BASIC environment. The machine was versatile, having very good-for-its-time graphics and multi-colors. Expansion capability for educational and experimental use with an assortment of I/O ports, which included a 1 MHz bus, user port, and cassette interface.

The BBC Micro was known for its reliability and emphasis on teaching programming and computer science. The system software, Acorn MOS, was simple and intuitive. With peripherals such as floppy drives and second processors, it performed tasks well beyond its initial use and extended its lifetime by at least a decade or more.

The BBC Micro also pushed forward a lot of gaming and software since this open architecture inspired a thriving community of developers. It also played a big role in the development of the ARM architecture by Acorn Computers, which would change the way modern computers are made in years to come. The BBC Micro has a special place in computing history, which expanded education and brought computing to schools and society through the 1980s.

🎄💾🗓️ Day 16: Retrocomputing Advent Calendar - Tandy 1000🎄💾🗓️

Tandy's 1000, sold by Tandy Corporation in 1984 via its RadioShack stores, was a low-cost home computer designed to be compatible with IBM PC software. It shipped with an Intel 8088 processor, 128 KB of RAM, expandable to 640 KB, and had better-at-the-time graphics and sound than many of the standard PCs. The 1000 had the Tandy Graphics Adapter, or TGA, and the more superior SN76496 or NCR 8496 sound chips. The built-in joystick port also made it desirable for gamers and home users. Different models were produced, each with improved hardware, before being discontinued in 1993. One of the main selling features was its compatibility with IBM-PC, the MS-DOS operating system, and expansion slots for peripheral devices.

And check out our guide! Tandy 1000 Keyboard to USB with CircuitPython. https://learn.adafruit.com/tandy-1000-keyboard-to-usb-with-circuitpython