In this post, I install a drive selector in my Amiga 500 Plus, letting it boot from USBs and a Gotek instead of floppy disks.
Introduction
So, remember that YouTube channel I started? Yeah – me neither.
Well, it’s back! I recently won an eBay auction for an external Gotek and Amiga 500 drive selector, and that gave me the nudge I needed to make a video!
This isn’t me chasing YouTube stardom. Rather:
- In my recent YearCompass post, I said I was going to target cultivating a Maker Mindset and setting Meaningful Milestones. And this very much qualifies! Not everything has to be cutting-edge or cloud-based.
- I had some great advice from Compton Harry about spontaneity and getting comfortable while being filmed. This is a continuation of that advice (Thanks man!).
- Filming things that don’t really matter is great practice for the things that do.
In this post, I will cover some key concepts for those less familiar with 90s Commodore hardware, explain what happened during filming and then leave you with the finished video. Watch me flailing with drives and chips for 20 minutes!
Let’s begin with some explanations.
Some Key Concepts
Before jumping into the video, it’s worth covering the hardware and installation steps involved.
About Goteks
The Gotek floppy emulator was originally developed by Gotek System, based in Shenzhen, China, primarily for the industrial sector.
Original Gotek Design
The Gotek was originally designed to replace 3.5-inch floppy drives in legacy hardware such as CNC machines, aviation devices and musical workstations. Many of these machines depend on floppy disks for data input, making them difficult to operate as working floppy disks become harder to find.
The Gotek functions as a hardware bridge by emulating the electronic signals of a mechanical floppy drive. Instead of using physical disks, the emulator reads digital disk images from a standard USB flash drive. USB drives can store and manage multiple virtual disks, offering modern storage reliability without requiring invasive modifications to the host machine’s internal components.
Modern Gotek Usage
Gotek capabilities have greatly improved over time, thanks to people like Keir Fraser, the creator of the open-source FlashFloppy firmware. While basic Gotek models are still available, most enthusiasts now use FlashFloppy for compatibility with a wide range of vintage electronics.
Over the years, several Gotek models have been released. Current hardware options often include usability enhancements like OLED screens for clearer file navigation, rotary encoders for quick file scrolling and built-in speakers that mimic the seek sounds of traditional drives.
About Drive Selectors
An Amiga drive selector is a device that switches the signals between the internal floppy drive and an external drive.
Why Are Drive Selectors Needed?
In the Amiga architecture, the internal floppy drive is designated as DF0, while external daisy-chained drives are assigned as DF1, DF2 and DF3. This hierarchy is fundamentally tied to how the hardware and software interact.
The earliest Amiga 500 models used Kickstart 1.3, which has no user-accessible way to select an alternative boot drive. Later Kickstart versions, starting with 2.0, introduced the option to select a boot drive through the early boot menu:
However, a significant issue remained: the software itself. A lot of classic Amiga software used custom trackloaders. These were low-level routines that bypassed AmigaDOS and read physical disk tracks directly. Developers used them to improve loading speed, reduce memory use and add copy protection.
By bypassing AmigaDOS, these NDOS (Non-DOS) disks could:
- Load faster by reducing drive head movement.
- Conserve memory by not loading the full OS disk-reading library.
- Prevent piracy through non-standard disk formatting.
The downside was that many of these disks were hard-coded to expect DF0. Even if a program was launched from DF1, it might still look for files or data on DF0. If DF0 was empty, the Amiga would crash or simply hang.
That is where a drive selector becomes useful. Rather than changing the software, the selector changes the hardware’s view of the drives.
How Drive Selectors Operate
Drive selectors are available as switched and switchless versions. Mine is from AmigaStore.eu, judging by the PCB markings.
To understand how a drive selector works, one must look at the 8520 CIA (Complex Interface Adapter) chips on the Amiga motherboard. Specifically, CIA-A (located at address $BFE001) is responsible for handling the floppy disk interface signals, including the Drive Select lines.
Upon boot, the Amiga identifies which drive to talk to using four active-low Select signals: _SEL0, _SEL1, _SEL2, and _SEL3.
_SEL0triggers the internal driveDF0._SEL1triggers the first external drive portDF1.
A drive selector sits between the CIA-A chip and its socket. It intercepts the relevant traces and swaps the logic lines when activated:
- The
_SEL0signal coming from the CIA is routed to the motherboard’sDF1circuitry. - The
_SEL1signal is routed to the internalDF0circuitry.
Because this happens electrically before the signal reaches the drive cables, the Amiga does not know anything has changed. It still believes it is talking to the internal drive, but the signal is actually being redirected to the external Gotek.
That gives a level of compatibility that software-based drive remappers cannot always match. Even persistent trackloader-based software will treat the Gotek as if it were an internal drive.
Video
Here’s the full video walkthrough of the install – droppages, shark noises and all!
Video Summary
In the video, I open my 1991 Amiga 500 Plus and install a drive selector PCB. I took a fairly quick-and-dirty approach and worked around the internal components, but in hindsight I should have removed the floppy drive entirely to give myself more room.
The installation involves carefully removing the Even CIA chip from its socket on the motherboard. I then connect the drive selector PCB to the original 40-pin socket and place the chip into the selector.
After that, I test the setup with an Amiga Test Kit floppy disk and a Cannon Fodder ADF. The selector successfully redirects the DF0 boot signal to the external Gotek, letting me boot from USB while keeping the original internal floppy drive fully functional.
This is not presented as the optimal method – retro hardware can be unpredictable, and a cleaner approach would involve removing more components before starting.
Video Chapters
If you prefer, you can jump to specific sections using the chapters below.
- 00:00 – Introduction
- 02:08 – Explaining the DF0/DF1 boot problem
- 02:53 – The Drive Selector PCB & Toggle Switch
- 03:59 – Opening the Amiga (Safety First!)
- 04:32 – Identifying the Even CIA Chip (U8)
- 06:04 – The delicate art of chip extraction (and bending pins)
- 10:54 – Amiga 500+ Hardware: Agnus, Denise, and current values
- 12:37 – Installing the Switcher & Re-seating the CIA
- 16:35 – The first boot & a mysterious Guru Meditation
- 18:46 – Success! Testing with Amiga Test Kit
- 20:05 – Final Demo: Loading Cannon Fodder from the Gotek
Technical Errata & Clarifications
- 02:08 – I called it a “Godrive,” I meant Gotek.
- 09:25 / 10:11 – I mentioned “bent chips” – I meant the metal pins/legs!
- 11:14 – Confirming: The 8375 Agnus is the 2MB Chip RAM version. Standard A500 Agnuses (8370/71/72) only support 512KB or 1MB.
- 17:15 – The Guru Meditation was likely a seating issue with the CIA adapter. If the pins aren’t making perfect contact, the CPU will throw this error immediately.
- 17:53 – The ticking sound is the stepper motor resetting to track 0. It has nothing to do with the drive heads.
Plus I erroneously call it a ‘Drive Switcher’ throughout. Oops.
Summary
In this post, I installed a drive selector in my Amiga 500 Plus, letting it boot from USBs and a Gotek instead of floppy disks.
I had fun with this! Which was the point! It was a chance to work on something familiar in a cosy space, and get more comfortable on camera while doing it. This and the recent Kubernetes lab reminded me why I like retro projects so much: they are practical, technical and just unpredictable enough to keep things interesting.
Like this post? Click the button below for links to contact, socials, projects and sessions:
Thanks for reading ~~^~~
