SD Card Interface Round-Up

If you're a collector, you'll be familiar with the mixed senses of excitement and foreboding when unboxing a vintage computer. Yes, tuning into that modern LED TV is a pain, but I'm talking about loading 30-year old software via the traditional mechanisms. Old tapes struggle and disks are even worse. But a handful of technical boffins out there have felt our pain and created a remedy - SD Card interfaces. This article will give you the lowdown on the latest and greatest of them.



What are SD Card Interfaces?

Put simply, they connect to your favourite vintage computer and allow that computer to load software directly from a modern-day SD card. Of course, each vintage computer brand has a different set of ports to interface to the outside world, and floppy disk drive and cassette interfaces are no exception. As a result of this lack of standardisation between platforms a variety of bespoke devices have been built specifically for each computer, or for a group of computers that share the same interface.


How Much Do They Cost?

Prices vary, depending on the cost of manufacture and the intention of the developer to make a little profit on their inventions. The cheapest we've seen is the uncased version of the SD2IEC for C64/128 and VIC-20, at just under £40. At the high end of the market are the SD2SNES for $190 (approx. £125 at the time of writing this article) and the 1541 Ultimate II for the C64 and C128 which implements a real 1541 floppy drive for 100% compatibility.


Can I Get One for Machine X?

Good question, and the quick answer is, ... maybe. The vintage computing market is too small for commercial manufacturers to bother creating their own SD card interface, but fortunately a good number of the more common machines have got enough of a fan-base that the Engineering-minded among them have rolled up their sleeves and toiled for days, weeks, months, to produce a modern means of talking to Machine X so that the rest of us can play our fave games without the hassles. One SD card worth a few pounds is often more than enough capacity to store the entire collection of titles for a given platform. Your tapes aren't going to be sold or binned as a result of getting one of these, but they can take that well deserved rest and just look nice on the shelf!

Let's take a closer look at some of these SD card interfaces, namely:

* DivMMC EnJOY! for the Sinclair ZX Spectrum

* SD2IEC for the Commodore 64, 128, VIC-20, C16 or Plus/4

* GoSDC for the Acorn BBC Micro

* Harmony Encore for the Atari 2600

* ZXpand for Sinclair ZX81, TS/1000 and TS/1500


There are a number of others which we've not yet reviewed, including the HxC Floppy Drive Emulator which can replace the standard floppy drive on Amiga, Atari ST, Amstrad CPC6128, and PC, there's the Everdrive range of cartridges that support Sega Mega Drive/Nomad, Game Boy/Color, SNES, PC-Engine/Turbografx-16, Sega Master System, Famicom/NES, Nintendo 64, and Game Gear. Also an Amstrad DDI-1 clone to allow CPC464/664 owners to use a floppy drive (or the HxC). This article will be expanded in future iterations to include reviews of these also. If there are any SD card interfaces I've missed and you'd like to see a mini-review on this page, write to us!


DivMMC EnJoy!

For ZX Spectrum fans, there's the DivMMC EnJOY! Created by Ben Versteeg (, this is a feature-packed unit that connects directly into the expansion port at the back of the ZX Spectrum. It permits saving and loading of programs to the SD card directly from BASIC using new commands. It can create snapshots of games so you can stop playing, save, and continue where you left off at a later point in time (like a "Freeze Frame" cartridge), and it's compatible with every model Spectrum: 16K, 48K, +, 128K, +2, +2A, +2B, +3 and some clones. It doesn't support 128K BASIC, but will happily run Spectrum 128K programs.

There are two versions currently available, the DivMMC EnJOY! which is the circuit board without the casing, and the DivMMC EnJOY! Black Edition which you see to the left. The Black Edition is very attractive, and is designed to blend in with the rest of the Sinclair hardware perfectly.

It comes with embedded ESXDOS on a programmable EEPROM chip inside the DivMMC EnJOY! ESXDOS adds a powerful "disk" operating system to your Spectrum, with support for DivMMC and DivIDE (an IDE hard disk, ZIP drive and CD-ROM interface for the Speccy) devices. You can write to FAT16 and FAT32 standard partitions on the card, read and write to .TAP tape images, and much much more. ESXDOS is being updated all the time, with the current firmware version at 0.8.0 in public BETA. You can upgrade this firmware easily through a jumper setting on the board and a valid firmware file on the SD card.

The DivMMC EnJOY! supports SD, SDHC, and MMC cards. An extra bonus is the reset button on the top of the unit, and a Kempston-compatible joystick interface, so 16K/48K owners don't have to forego the use of a joystick when the DivMMC EnJOY! is plugged in.

Using the DivMMC EnJOY! is a breeze. It comes with a pre-formatted 4GB SD card with some games and demos to get you started, and a brief but easy-to-understand user guide that runs you through the basics of setting the jumpers on the board for the model of Spectrum you're connecting it to, how to put tape and disk images onto a formatted SD card from your PC, and then the simple commands to load those files on the Spectrum. Supported file types are currently .TAP tape images, .SNA snapshot files, and .TRD TR-DOS files. I was up and running in about 10 minutes from unpacking to playing a game.

To load a game from SD card, you simply press the NMI button on the DivMMC, and up pops the list of files on the SD card. Using the cursor keys you can highlight the file of your choice and hit enter to run it. Games load in a seconds. One minor issue I had was that I loaded the SD card up with far too many files - trying to get to the file in the list on the Spectrum took a while, and you have to scroll down a lot. There are no keyboard shortcuts, e.g. pressing 'M' to jump straight to the files starting with the letter 'M'. This would be a useful addition, as would support for directories. Two LEDs on the unit provide indication of 'Power on' and 'Card activity'.

At the moment, the DivMMC EnJOY! doesn't support long filenames, the use of wildcards in BASIC commands, or extended partitions. But there's a lot more to this little device than just mass-storage access, and whilst it's a little pricey at around £50+P&P for the uncased model and £60+P&P for the Black Edition, for the active Spectrum user I would consider it an essential part of my collection.

Purchasing the DivMMC EnJOY! is straightforward. Ben sells them through his Ebay Shop (Ebay user id = bytedelight), and also through his own Byte Delight website. It took around 1 week from ordering to receiving my unit.

Pros: Powerful ESXDOS in firmware gives much more than just SD card access, easy to use menu system, informative user manual.
Cons: A bit expensive. Sticks out from back of machine quite a bit, no expansion slot daisychain (for other devices to be used at the same time, e.g. Currah Micro Speech)



SD2IEC for Commodore 64/128/VIC-20/C16/Plus/4

The SD2IEC from The Future Was 8Bit emulates the basic functions of the Commodore 1541 floppy disk drive (Drive 8), thus taking the place of one of the two very large brown or grey boxes on your desk. I was very impressed with the SD2IEC physically. It's tiny, it's been professionally built, and it's been made to look just like a baby 1541 floppy drive!

The feature list of the SD2IEC is as follows: support for fast loaders including JiffyDOS/Epyx FastLoad/Final Cartridge III/TurboDisk/Speeddisk/Dreamload, FAT16 / FAT32 SD cards, multi-disk games, and directories. D64, D81, D71, M2I as well as PRG's are acceptable file formats recognised by the SD2IEC.

Loading speeds are the same as the original 1541, but since the device doesn't use the cartridge slot on the computer, it can be sped up through the use of an Epyx FastLoad or Final Cartridge III cart. It doesn't support everything the 1541 is capable of, so some programs that require 100% true drive emulation can fail, although these a few and far between.

Using the SD2IEC is simple if you've previously used a Commodore floppy drive, as you use the same commands. To get the directory of the "disk", you type "LOAD "$",8. To load the first file type LOAD"*",8. For multi-disk games, there is a very handy Disk Swap button on the top of the unit. When used in combination with a special file called "autoswap.lst" in the game directory which contains a list of the game disk images, e.g. thelastninja_1.d64, thelastninja_2.d64, thelastninja_3.d64, it will cycle through the disks whenever the Disk Swap button is pressed. Very handy!

When you purchase the SD2IEC, you're given the option of several methods of powering the device ranging from a mini-DIN cassette connector (C16 or Plus/4), to a flat Datasette connector (for VIC-20/C64/128), to a User port connector (all but C16), a combination of the above for maximum usability, or simply USB powered (if you opt for mini-DIN, Datasette or User port connectors, the SD2IEC draws its power from the computer so no external power supply is required). This is a great set of options, as only you know if you're likely to be using the SD2IEC alongside a real Datasette, or you have another device using the User port. You can even purchase a FastLoad cartridge for an extra £15.99 when ordering your SD2IEC.

Prices start from just £39.99

Pros: Tiny, unobtrusive unit. Emulates the 1541 so you still get that authentic feeling of loading software from 'disk'. Available in several colours including beige, grey, black, transparent, smoked, and even genuine recycled C64 plastic!
Cons: Some extended 1541 instructions are not supported, so not all software will run.


GoSDC for the Acorn BBC Micro

For Beeb fans, we have the GoSDC, a storage system for the Acorn BBC model B, BBC Master and Electron. As with the SD card interfaces above, the GoSDC stores your files on an SD, SDHC, or MMC flash card, up to 32 GB in capacity. The GoSDC is the brainchild of John Kortink who was previously responsible for the GoMMC, a predecessor of the GoSDC, and a number of other modern-day Acorn peripheral replacements.

The GoSDC supports 'areas' so you can split up your media collection into disks and tapes, for example. The GoSDC's ROM has all the DFS/ADFS filing systems and tools embedded on it, so you don't need to have any special software on the SD card, just your own files. Updates to the GoSDC ROM can be achieved quite easily via a FAT-formatted SD card and running the firmware update tool. John provides firmware updates via his website, the current version being 1.05, released on 1st September 2014.

Installing and using the GoSDC is quite simple, although slightly more involved than a cartridge-style interface which is simple plug & play. Getting the GoSDC up and running is a 4-step process:

1) Install the hardware == In the package, you get the GoSDC ROM board, an 'adapter' ROM socket with a wire connected to one of the pins, and a 16MB MMC card. You install the GoSDC into any spare ROM slot inside your Beeb, the adapter ROM into another free slot, and connect the adapter ROM's wire to the GoSDC. This adapter ROM allows the BBC to use another of its ROM slots to hold a DFS or ADFS file system - the GoSDC does the clever work in telling the computer that a DFS/ADFS ROM is installed in that slot.

2) Setup the SD/SDHC/MMC card == This is probably the most involved part of the setup. Insert the card into the GoSDC and power up the Beeb. Run a format command, and it will format the area on the SD card with a proprietary format. To get disk (or tape) images onto the SD card, connect the SD card back to your PC or Mac, and install .ssd images onto the SD card using the GoSDCio utility.

3) Choose a DFS/ADFS file system that is suitable for your model of BBC == Put the SD card back into the GoSDC. Then, by running a couple of *SDCCONFIG commands on the BBC, you can instruct it to populate the adapter ROM slot with one of a number of built-in DFS/ADFS ROMs. After restarting the computer, you can insert your disk images using *SDCDISC commands, and run them as if they were regular disks using commands such as *. and LOAD"<filename>".

The GoSDC works on vanilla BBC model Bs from OS 1.20 and up, and best of all, you do not have to have the Floppy Disk interface (1771 or other) installed for the GoSDC to work. It works on BBC Masters with MOS 3.20 or 3.50, and most Electrons with the addition of an optional special "GoSDC-to-Electron' interface.

GoSDC works great with DFS (.ssd) and ADFS Disc images. Tape images (.uef files) can be 'played' but no 'record' functionality exists. I was very impressed with the depth of documentation provided on John's website, plus his speedy response to my emails when I got a bit stuck during setup. My only small criticisms are that there is no Quick Install Guide provided in the packaging, and the GoSDCio utility didn't want to work with the SD card in my PC (I had to use a Mac, which ran fine with superuser access). The items were well protected for transit, and the physical hardware appears to be manufactured to the highest quality.

Two versions of the GoSDC are available:

* MBE version: supports BBC model B, BBC Master and Electron only. Provides the highest read and write performance.
* UNI version: supports additional machines and hardware, e.g. BBC model B+, but has lower write performance (100KB/sec vs 150KB/sec).

The GoSDC can be purchased directly from John Kortink via Paypal for 60 Euros plus shipping costs (I was quoted 9 Euros shipping to the UK + 3 Euros Paypal seller fees), so total 72 Euros (approximately £52 in sterling). Keep checking Retro Isle's News for a full write-up on installing and using the GoSDC in the coming weeks.


Harmony Encore for the Atari 2600

The Harmony Encore went on sale at the start of 2014. An evolution on the previous Harmony, this flash cartridge is designed and manufactured by a group of Atari fans on the AtariAge website: Fred Quimby, Chris Walton, Stephen Anthony, Delicon, Thomas Jentzsch, John Payson, Nathan Strum, and Albert Yarusso. The Encore expands the ROM size to 512K and RAM size to 1 MB to support bigger indie games, as the Encore's design aim was to be able to run 100% of Atari 2600 software, both old and new. Currently I'm told it is able to play at least 98% of old 2600 games, but the firmware can be updated as and when new versions come out to further enhance its compatibility.

Most Atari 2600 game binaries found online have a .bin file extension, and the Encore automatically detects the type of file when it is loaded. Most files work out of the box, but sometimes this auto-detection fails. Fear not however... the Encore is also able to read other file extensions that force it to use a specific memory bankswitching method to match the original cartridge's bankswitching. For example, you would rename a file from .bin to .f4s to tell Encore that the file uses Atari F4 bankswitching with Superchip.

Using the Encore cartridge is very easy. Simply plug the cartridge into the top of the 2600 as you would any other game cartridge. Put your favourite game files on the SD card, put the SD card into the Harmony and switch on. You are presented with the list of game files which can be selectable using the controller.

The Harmony and Harmony Encore cartridges are both sold through the AtariAge website here for the sum of $59.99 (Harmony) $84.99 (Harmony Encore). Shipping to outside of USA and Canada costs a further $12.00 for economy or $26 for priority. You have a choice of SD or micro SD for the same price.




ZXpand for Sinclair ZX81 and Timex equivalents

Released in 2011, the ZXpand interface by Charlie Robson/EightyBits for RWAP Software acts as both an SD card interface and a backbone for further expansion devices. The SD card part of it provides support to directly load and save .p files which is the format used by most ZX81 emulators.

The interface also provides the ZX81 with a further 32K of RAM which can be used for various high-resolution graphics schemes, a reset button, new keywords added to BASIC to support the load/save functionality, produce a catalogue of files on the memory card, configure the ZXpand interface and delete files. It has full support for directories on the SD card, and you still have the option of loading and saving via traditional cassette recorder, which can act as a great way to load programs in from a tape and then save it on the SD card.

A file browser has been written by kmurta of the forums. It permits easy navigation of your files and directories on the card using the Q and A keys, and ENTER to go into the directory or to load the file. Once a program has been loaded, the ZXpand's ROM can be easily switched off to provide the original functionality of LPRINT, LLIST and COPY commands.

The ZXpand's firmware can be upgraded via SD card.

The backbone part of the ZXpand is that you can also purchase other expansion cards, such as the ZXpand-AY sound interface which provides full support for the AY-3-8910 sound chip to the ZX81 including new BASIC commands. Another expansion interface available for the ZXpand is an Atari-style joystick adapter.

We're told that whilst the ZXpand works fine on the unexpanded ZX81 and TS/1000, using it with TS/1500 will impede access to the ear, mic and TV sockets. It also cannot work on a ZX80 without the use of a replacement ROM inside the ZX80. No casing is provided for the ZXpand, but the circuit board is sized to fit snugly inside a Memotech memory expansion case with some modification to allow access to the card slot.

The ZXpand interface is available to purchase from the website for £50 plus £5.05 P&P.



SD Card Interfaces - Feature Comparison Table

  Sinclair ZX Spectrum DivMMC EnJOY! C64/C128/VIC/C16/Plus4
Acorn BBC Micro
Atari 2600
Harmony Encore
Sinclair ZX81
Cost: From £57 From £40 €72 From $72 £55.05
Maximum Capacity: - - 32 GB 32 GB -
Format: FAT16, FAT32 - Proprietary FAT12, FAT16 or FAT32 FAT12, FAT16 or FAT32
Card Provided?: Yes, 4 GB £4.99 Yes, (16MB MMC) No No
Physical Dimensions: - 13x38x70mm (WxHxD) 62x35x8mm (LxWxH) - -
File Formats Supported: .TAP, .Z80, .SNA and .TRD D64,D71,D81,M2I and PRG Disk Image files - .SSD and .ADF
Tape Image files - .UEF
.BIN files with 2K, 4K, F8, F8SC, F6, F6SC, F4, F4SC, FA, FE, 3E, 3F, E0, E7, CV, UA, Supercharger, DPC, 0840, Custom bank-switching
Power: by Computer by Computer or USB by Computer by Computer by Computer
Read/Write Performance: Almost instant As 1541 floppy drive Almost instant Almost instant Almost instant
Firmware Upgradable: Yes, via SD card Yes, via SD card Yes, via SD card Yes, via USB port Yes, via SD card
Extras: Kempston joystick interface, reset button Disk Swap button, Reset button Adapter ROM - Support for other enhancement boards


This page was last updated on 2nd February 2015.