I am now selling my ZX Spectrum Expansion System project as a made up and tested device. This page clarifies some of the details.

This is an updated version of the device for 2026. It has had a software uprade, and now has a really nice case made from resin. Structurally it's much stronger than earlier versions, using internal brass standoffs and better quality screws and connectors. The finish is a vast improvement on the FDM 3D printed case it used to have.

The device simulates the behaviour of the ZX Interface 1 with 8 microdrives attached. It works at the Z80 instruction level and is, to the best of my knowledge, totally compatible with all software written for the microdrive, even custom written machine code which bypasses the Interface 1 ROM code.

Technically the device is a simulation of the system, not an emulation of the hardware. It's a subtle difference which in lay terms means you can't plug a real microdrive into it, that's not its function. Also, it only simulates the Interface 1's microdrives. It does not simulate the ZX-Net network or the RS232 port.

The device uses a micro SD card to store MDR image files. The MDR microdrive image file format is widely supported among ZX Spectrum emulators, so the typical usage pattern is to either download MDR files from a ZX Spectrum archive such as Spectrum Computing, or create MDR files from scratch on a PC using an emulator like Fuse. You can also manipulate MDR image files using tools such as Tom Daly's Z80onMDR transfer tool. The current version of the user interface on the device itself is limited to loading and ejecting MDR files into the simulated microdrives, so you need to copy, move, rename, etc., those files on the the SD card using the PC. Working with the contents of the MDR image files is all done on the Spectrum, just like it was in 1984.

This is a device made for the 48K ZX Spectrum. I think it will work with the 128K Toastrack and the +2 Grey, but I don't have those machines so I can't test with them. Electronically it should work, but whether it fits physically into the back of the machine without obstructing ports I don't know. If you have those machines in mind, buy at your own risk (then send me feedback). The device will definitely not work on any of the later Amstrad machines as they use a very different ROM subsystem.

The ZX Spectrum Expansion System device is an open design with open source software. You can make one yourself free of charge. I provide this production service for those who don't have the time and/or skills and/or equipment to make one. Just to be crystal clear on that: I'm not selling the device, I'm charging an engineering fee for those who don't want to make a device themselves.

As per the licence for the original design, the device and its software are supplied in the hope it will be useful, but it comes with no warranty of any kind, express or implied, including the warranties of merchantability and fitness for a particular purpose. I do guarantee my engineering though. I'm a hobbiest, not a commercial shop, and the device is complex with every joint soldered by hand. Obviously I test everything, but I can make mistakes so if it doesn't work, or it stops working in the 12 months after sale, I'll fix or replace it free of charge. This only applies if any tamper resistant tape is still in place.

The device is priced at £75+p&p for direct sales using Paypal friends and family payment, or bank transfer. Where it's on reseller markets like eBay the price is typically a little higher since those platforms present me other costs.

You need a micro SD card, just a small one since even a 64MB card will easily hold hundreds of MDR files. Many people have an old SD card laying around. If not, I can supply a 64MB no-brand micro SD card with a few MDR image files on it to get you started. That's £5 extra.

Postage for the UK is the Royal Mail's Tracked48 service which delivers in 2 to 3 days. That costs £3.95. Faster services are available. People from outside the UK should contact me to discuss shipping and duties and such. We can work something out.

Purchase options, therefore, are:

I try to keep at least 2 or 3 on the shelf, but sales are a bit random so please contact me to check immediate availability.

Goodness, that's a lot to read. I'm honestly not trying to introduce a whole load of small print, I'm just trying to cover myself from scammers and people who like to try to pull a fast one. If you want to buy a device, or if anything needs clarifying, please contact me.

Derek Fountain, derek@scratters.com