The Ultimate 1541 Talk by Michael Steil, presented at the Vintage Computer Festival West

The Ultimate Commodore 1541 Drive Talk: A Deep Dive Into Disks, Controllers, And Much More

When we think of retrocomputing, it’s very often the computers themselves that get all the glory.  There’s nothing wrong with this of course- the computers of the late 70’s and 80’s were incredible machines that were chock full of hacks in their own right. But some of the most interesting hacks of the day happened not in the computers, but rather in their peripherals. A devotee of such periphery is [Michael Steil], who was driven to compile years of research, knowledge, and hard data into The Ultimate Commodore 1541 Drive Talk which you can view below the break.

In the talk, [Michael] covers the physical disk composition and construction, the disk drives, controller hardware, and the evolution thereof. The bit-by-bit breakdown of the tracks, sectors, and header information on the disks themselves is fascinating, as is the discussion of various copy protection techniques used by vendors to prevent piracy at a time when sneakernet was in full swing.

The descent into the circuitry of the controller reveals a venerable 6502 CPU which powered many vintage computers. Further discussion divulges the secrets for getting higher performance from the 1541 drive using innovations that are as recent as 2013.

A computer historian and archaeologist, [Michael] discusses how using modified vintage hardware is sometimes enough to save your old floppy collection. He also shows how modern interfaces that read disks all the way down to the magnetic flux level can be used to reconstruct missing data.

[Michael] masterfully lays bare the complexity, engineering, and hackery that went into storing less than 200kb of data. Whether you’re a Commodore enthusiast or not, your appreciation for the 32GB USB stick collecting dust on your desk is bound to grow!

We’ve covered [Michael]’s exploits before, and you may wish to check out the Ultimate Apollo Guidance Computer Talk or the Ultimate Gameboy Talk. Do you have your own favorite retrocomputer hacks and insights to share? Be sure to let us know via the Tip Line!

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David Murray and Kevin Williams with an early X16 prototype

Commander X16: A Dreamy 8 Bit Computer Comes Closer To Reality

Imagine the ultimate homage to 1980s 8-bit home computers. It might  look like [David Murray] aka The 8-Bit Guy’s Commander X16.

As a core group of geeks, hackers, and developers age, we yearn for the computers of our youth. VIC-20s, Commodore Pets, 64s, 128s, Ataris, Apple IIes, and the list goes on and on. For many of us, our first hands on experience with a computer was with such a machine that is now called “retro”. Sadly, many of these relics are getting more expensive as demand increases and supplies dwindle. Working examples are harder to find, and even those can break down. Original monitors, peripherals, and accessories are also getting scarcer. This is all quite understandable when we consider that some of these classics are over 40 years old.

What was it that we loved about these old rigs that makes them so attractive? [David] decided to distil what makes a classic a classic, and then turn that list into a spec list for what he calls his “Dream Computer”. He found that things like a printed and spiral bound manual were a big part of the charm and utility of these early home computers. Booting directly to a prompt and being able to directly control the hardware was another highly desirable trait.

[David] also took the time to determine what people don’t like about these retro machines: Wacky keyboard layouts, composite video output, and glacially slow storage. Swapping multiple floppies to load a program or respooling a cassette tape is just as undesirable in 2021 as it was in 1981. Who knew?

X16 Prototype #3
The X16’s’ prototyping is still in progress.

The result of [David]’s research is the Commander X16. Inspired by the VIC-20, it’s a fresh take on the retrocomputer that only uses parts that are currently available. You can see the first video in a series about the development of the X16 below the break. Be aware that a lot of progress has been made since the video came out in 2019, but it still provides an excellent starting point for learning about the project.

The X16’s specifications read like dream list made in the mid 80s: 256 color VGA, up to 2MB memory, an 8 MHz 6502, plenty of expansion ports, and even ports for SNES style controllers.  And what else will this dream machine include? You guessed it: A spiral bound manual!

It’s not possible to list all of the great features of the X16 in this space, so check out the Commander X16 FAQ for all the details. If this project makes your heart go pitter patter, you may be interested to know that they need help with software development! An emulator is available for development. The goal is to have a healthy software ecosystem in place when the X16 launches.

You may also enjoy reading about other 6502 retrocomputer reports such as this “Brain in a vat” 6502 computer, or a guided tour of the birthplace of the 6502 and the Commodore 64 with our very own Bil Herd.

Thank you to [Truth] for bringing us a report of this fine project via the Tip Line. Keep those tips coming!

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Cerberus 2080 — Three-Headed Retro Computing Project

For seven months, [Bernardo Kastrup] at [TheByteAttic] has been realizing his childhood dream of building his own computer. It was this dream that steered him into the field of computer design at the age of 17. After thirty years in the industry, he finally has some time to design the computer he dreamt about as a kid. His requirements are ambitious: fully open design, gate-level details, thru-hole or PLCC for easy hacking, well-established processors with existing tool chains, low-cost development tools for CPLDs, no FPGA, standard ITX case compatible, and so on. He quite reasonably decides to use more modern electronics for video (VGA), keyboard (PS/2), and program storage (flash drive). Along the way, he chooses to put three processors on the board instead of one:

  • Zilog Z84C0010 (Z80)
  • WDC W65C0256 (6502)
  • AVR ATMEGA328 (RISC Controller)

When coming up with the concept and requirements, [Bernardo] had a fictitious alternate history in mind — one where there were follow-ups to the ZX80, PET/CBM, or TRS-80 from the late 1970s that were extensions to the original systems. But he also wanted a clean design, without cost-cutting gimmicks, in order to make it easier for learners to focus on computing itself — a didactic architecture, as he describes it. Turn the crank for seven long months, and we have the Cerberus 2080. [Bernardo] has put the design on GitHub, and made a video series out of the whole process, of which the introduction video is below the break. There’s even an online emulator developed by retro hacker  [Andy Toone].

We wrote about the 6502-based ERIC-1 project back in 2014 which shared the bus with an ATMEGA simulating ROM. The Minty Z80 project from 2019 also uses a similar technique. Thanks to [Frédéric] for sending us the tip.

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Gorgeous 6502 Celebrates Craftsmanship Of The Early Homebrewers

The days when a computer had a front panel bristling with switches and LEDs are long gone, and on balance that’s probably for the better in terms of ease of use, raw power, and convenience. That’s not to say there aren’t those who long for the days of flipping switches to enter programs, of course, but it’s a somewhat limited market. So unless you can find an old IMSAI or Altair, chances are you’ll have to roll your own — and you could do a lot worse than this aluminum beauty of a 6502 machine.

The machine is named PERSEUS-8 by its creator, [Mitsuru Yamada]. It follows earlier machines bearing the PERSEUS badge, all of them completely homebrewed and equally gorgeous. The PERSEUS-8 would have been an impressive machine had it come along 45 years ago — the 2 MHz version of the 6502, a full 16-bit memory address space, and 16 kB of battery-backed RAM. But the mechanical and electrical construction methods and the care and craftsmanship taken are where this build really shines. The case is fabricated out of aluminum sheets and angles and looks like it could have come from a server rack. The front panel is to die for — [Mitsuru] carefully brushed the aluminum before drilling the dozens of holes needed for the toggle switches and LEDs. And the insides are equally lovely — socketed chips neatly arranged on perfboard with everything wired up using period-correct wirewrap methods. Even the labels, both on the front panel and even on the motherboard, are a joy to behold.

Builds like this are the ones that really inspire us to take the extra steps needed to make our projects not only work, but also to be beautiful. We’ve seen this kind of craftsmanship from [Mitsuru] before — recall this serial terminal that never was, or the machine that came before the PERSEUS-8.

Diving Into The Details Of Keyboard Interfaces At The Gate-Level

Never doubt the value of a good teacher. Even if you know — or think you know — the material being presented, a good teacher can open your eyes to new ways of looking at things that will pay dividends you never expected.

That’s the feeling we got while watching [Ben Eater]’s latest video on building a keyboard interface (embedded below) for his breadboard 6502 computer. On the face of it, getting a keyboard to talk to a computer should be a simple job. [Ben] had previously looked at the serial protocol used by the old PS/2 keyboard and even built a wildly complex circuit out of discrete shift register chips to visualize the data being sent by the keyboard. The video below continues that work, this time concentrating on using the keyboard with his 6502 breadboard computer.

After some instructive preliminaries on interrupt programming, [Ben] dives into the logic-level details of teasing useful signals from the keyboard. His signal processing starts with some inverters and an RC network to turn multiple clock pulses into one logic level transition. Walking through this circuit step by step was the really interesting bit; even if you know that the answer is eventually going to be “Schmitt trigger,” getting to that point was really instructive.

Of course, what [Ben]’s videos mainly accomplish is making us want to follow along with him and build a breadboard computer of our own. From a low-rez VGA card to a reliable UART, following along with his discrete chip builds is always educational.

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Everything Old Is New Again: Another 6502 Board Is Born

[Jeff] says that designing your own 6502 computer is a rite of passage, and he wanted the experience. His board can accept a real 6502 or the newer CMOS variant that is still available. There are a few modern conveniences such as USB power and provisions for using a USB serial port.

We are spoiled today with microcontrollers having everything in one package, but with this class of CPU you need your own memory, I/O devices, and other support chips. [Jeff] took a traditional approach, but picked components that are still easy to obtain. Some designs now push all the support functions to a more modern processor like an Arduino, which is very simple to do, but doesn’t feel as authentic, somehow.

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Another Kind Of “Bare Metal”: 6502 Computer Powers RPN Calculator

[Mitsuru Yamada] states that one of the goals for this 6502 computer build was to make it strong enough to survive real-world usage. In that regard alone we’d call this a success; the die-cast aluminum enclosures used are a little blast from the past and lend a nice retro industrial look to the project. The main chassis of the computer fairly bristles with LEDs and chunky toggle switches for setting the data and address busses. The interior is no less tidy, with the 6502 microprocessor — date code from 1995 — and associated support chips neatly arranged on perf board. The construction method is wire wrapping, in keeping with the old-school look and feel. Even the hand-drawn schematic is a work of art — shades of [Forrest Mims].

As for programming, this machine is as low-level as it gets. Nothing but 6502 machine language here, entered manually with the toggle switches, or via an externally programmed ROM. The machine can only address 1k of memory, a limit which the code to support the RPN calculator add-on [Yamada] also built brushes up against, at 992 bytes. The calculator keypad has a 20-key matrix pad and an eight-digit dot-matrix LED display, and can do the four basic operations on fixed-point binary-coded decimal inputs. The brief video below shows the calculator in action.

We love the look of this build and we’re eager to see more like it. We’ve seen a ton of 6502 builds from discrete chips lately, and while we love those too, it’s nice to see one of the big old DIPs put back in action for a change.

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