As the gaming public's appetite for retro gaming has grown over the past few years, so too has the market for associated items which make the process of playing vintage games that bit easier. Modern systems are packed with downloadable retro titles that have been lovingly emulated for a new generation to enjoy, and we've seen the likes of the SNES Classic and Mega Drive Ultimate Portable arrive on the market, pre-loaded with some of the best games of their respective eras. However, for those purists out there who crave the authentic experience of original hardware, a flood of flash carts have appeared which allow you to play ROM images on your dusty old NES, SNES, Mega Drive and pretty much every other major console in existence.

Flash carts remain a grey area, despite the fact that many of the machines they're produced for have ceased to be commercial concerns for platform holders or developers. We've discussed the positives and negatives of such carts in the past, so we'll avoid needlessly repeating ourselves as much as possible; suffice to say, with every flash cart there comes the issue of piracy. While they allow you to enjoy a great many titles which are no longer available commercially for whatever reason, they also permit you access to titles which are still in circulation, either in re-issued form or as digital downloads.

Throughout the history of flash carts we've seen the major systems covered, and many of these – including the NES and SNES – have libraries that are either relatively cheap to purchase on the second hand market (with some notable exceptions) or are still actively being monetised via the likes of the Virtual Console platform on Wii U and 3DS. The rapidly-expanding nature of the retro gaming sector means that even niche systems are getting these carts; recently, a one-man operation in the UK produced the superb Neo Geo Pocket SD cartridge for SNK's massively underrated handheld rival to the Game Boy Color. Keeping with the SNK theme, Spanish firm Terraonion has created a flash cartridge for the legendary Neo Geo arcade and home video game system – and as you've probably gathered from the title of this feature, that's our main focus here.

The NeoSD – which comes in MVS (arcade) and AES (home) flavours – is noteworthy for several reasons. Firstly, there hasn't been a proper flash cart for the console so far (although bootleg multi-carts have existed for a while, but these are known to damage hardware in the long term) so this is a welcome development. Secondly, the extortionate cost of Neo Geo ownership means that this is perhaps the ideal console for such a product, especially if you're collecting the domestic AES variant of the machine. Popular titles such as the iconic Metal Slug cost many, many times more in their AES guise than they do in the arcade MVS form, despite being practically identical in terms of code. Even at the time of release AES games cost between £150-£200 each, and while the passage of time has resulted in low-cost second hand titles, many have become even more valuable due to the small print runs associated with AES software. Even on the MVS side of things, prices are still quite high.

Taking all of this into account, it's obvious why the NeoSD has caused such a splash amongst the Neo Geo community; while hardcore collectors will accept nothing but the original games – and are prepared to sell their vital organs to procure them – the more "casual" fans will no doubt see the benefit of having every single Neo Geo game on a single cartridge; even for the asking price of around $500, it's considerably cheaper than buying a complete library and means there are less boxes to store (Neo Geo games come in cases that are the size of an average hardback book). Not only do you avoid having to take out a second mortgage to afford your next game, you still get the benefit of playing on original hardware.

The NeoSD's appeal is increased by the fact that it's a breeze to use; you simply convert ROM images to a ".neo" format using the application supplied by the NeoSD team and load them onto a FAT32-formatted MicroSD card before inserting it into the cartridge. Booting up by holding the Start button gives you a complete list of the games, and pressing A transfers the game to the cartridge's 768 Mbits of flash memory, which is enough to hold the largest officially-released titles with a little bit of space left over for system software. The flashing process depends on the size of the ROM and the speed of the MicroSD card you're using, with some of the later (and larger) titles taking a few minutes to fully load. Once a game is flashed to memory, it will load instantly the next time you switch on your console, just like a real AES cart. To access the game list again, you hold down Start when booting up or hold Start + A + D for around 3 to 5 seconds when the machine is running.

The NeoSD's internal hardware – which is comprised of an ARM Cortex M4 and two Lattice XP2 FPGA chips – means that this is a powerful and reliable setup which won't damage your precious hardware in the same way some other flash carts can. The cart also allows you to switch the game region without tinkering with the BIOS, and it also accepts Neo Geo CD exclusive ROMs, such as Ironclad and Crossed Swords 2.

In short, it's a remarkable piece of kit and one that hasn't left our AES console since it arrived in the Nintendo Life office. Yet it leaves us in a rather sticky moral position, especially as we're all passionate supporters of the Switch. Japanese firm Hamster is slowly but surely working its way through the Neo Geo library with its Arcade Archives range, and since launch has populated the Switch eShop with classics such as King of Fighters '98, Samurai Shodown, Blazing Star, The Last Blade and Garou: Mark of the Wolves, to name but a few. We've gleefully snapped up the majority of these titles, all of which can be purchased for a tiny, almost insignificant fraction of what real AES and MVS cartridges exchange hands for on the secondary market. Surely, purchasing a device like the NeoSD and using it to play ROMs is like a slap in the face to companies like Hamster (and, by association, SNK itself), which are doing their utmost to ensure that these classic games remain playable for years to come, and can be purchased legally so that their creators benefit in monetary terms?

We're not here to lay own any moral or ethical guilt-trips, but in speaking from a purely personal perspective, the arrival of the NeoSD hasn't dampened our enthusiasm for Hamster's ACA Neo Geo range on Switch; far from it. In fact, having played some games on the NeoSD that we'd never experienced before, we've duly go on to buy the Switch version also. And besides, having purchased titles like Metal Slug and King of Fighters several times over on several different systems over the past few decades, we're not going to ignore the wealth of options now that the NeoSD is here; Neo Geo games on Switch offer a massive benefit as they're portable and can be played anywhere; they also come with new features such as high score tables and challenge modes. Perhaps most importantly of all, the Switch allows these games to become multiplayer attractions when you're out of the house; it's like having your own personal arcade you can take with you anywhere. 

The NeoSD may stop us from needlessly filling up our cupboards with AES cartridges – the purchase of which only benefits the current owner, as SNK sees no monetary reward on second-hand sales – but it won't stop us from seeking out Neo Geo games on other systems, especially – as in the case of the Switch – when they offer a more convenient, connected way to play. 

Thanks to Stone Age Gamer for supplying the NeoSD cartridge used in this feature.