SNK NEO GEO記憶卡是NEOGEO生態系中相當具有代表性的配件之一，它的誕生與設計理念，充分反映SNK在1990年代初期對「街機與家用體驗無縫接軌」的前瞻思維。這張小小的記憶卡，實際上在當年扮演跨平台存檔媒介的重要角色，讓玩家能把自己的遊戲進度與高分記錄，從街機帶回家中，或再從家用主機帶回街機，這在當時的遊戲產業中可說是極為罕見且先進的概念。

NEOGEO家用主機（AES）以及部分MVS街機機台，都支援JEIDA V3規格的記憶卡。只要是運行同一款遊戲的系統，就能插入記憶卡讀取存檔或高分資料，繼續遊玩。這種設計特別受到高分玩家與硬派玩家歡迎，因為它讓街機文化中「累積實力與成就」的精神得以被完整保存，而不再受限於單一機台。

在系統層面上，NEOGEO的SP-S2系統ROM（以及其他版本的系統 ROM）能夠支援從2KiB到16KiB、每2KiB為一級距的多種容量記憶卡。無論實際容量大小，遊戲都必須透過系統ROM提供的CARD呼叫來進行讀寫，而非直接操作記憶體位址，否則容易造成資料損毀。這也顯示SNK在設計時，已經考量到不同容量、不同電性規格卡片之間的相容與安全性問題。

在硬體規格上，NEOGEO記憶卡存在多種型態，包括8位元寬、16位元寬、16位元加倍型，以及被稱為「SNK ROM」的特殊卡片。市面上最常見、也是官方SNK所販售的版本，多半是8位元寬的卡片。雖然資料只使用低位元組，但存取時仍必須以16位元（word）為單位進行，這與68000處理器的匯流排設計與 /UDS 訊號有關，是硬體層面的限制。

原廠SNK記憶卡本身採用的是電池備份式SRAM，容量為2KiB，內部使用LH5116 SRAM晶片，並搭配電壓切換電路來維持資料。由於這顆電池並非可充電式，一旦電壓低於約2V，就有資料遺失的風險，這也是今日許多老玩家在使用原廠卡時最常遇到的問題。與MVS主機內部那顆可充電的備份電池不同，記憶卡的電池老化後只能更換，否則存檔將無法長期保存。

在外觀與內部設計上，目前已知至少存在兩個官方版本。較早期的版本使用的是標示為 C10075-X2-2 的電路板，後期版本則改為 EZ866 板型，兩者在電路布局上略有差異，但功能與相容性並無實質不同。這些差異如今也成為收藏玩家鑑別年代與版本的重要依據。

對於NEOGEO CD系統而言，SNK則採取不同的做法。CD主機內部內建一個「虛擬記憶卡」，實際上是一顆8KiB的電池備份SRAM，不需外插卡片即可存檔。這在使用上更為便利，也減少實體卡片遺失或電池老化帶來的麻煩，但同時也失去了在不同系統間自由攜帶資料的那種「街機感」。

在資料格式方面，所有NEOGEO記憶卡無論容量大小，基本結構都是一致的，差別只在於可用區域的大小。資料以64位元組為一個「區塊」進行管理，第一個區塊固定作為標頭使用。例如一張2KiB 的卡片，實際可用的資料區塊數量為31個。由於JEIDA匯流排為16位元設計，若直接存取8位元卡片內容，還需要特別注意位址倍增的問題，否則容易產生錯誤。

在市場反應與評價上，NEOGEO記憶卡在當年屬於小眾但高度象徵性的產品。對一般玩家而言，它並非必需品，因為多數街機遊戲本身就是短時高強度體驗；但對高分玩家、格鬥遊戲玩家，以及經常往返街機與家用主機的核心族群來說，它的價值極高。也因為NEOGEO主機與遊戲本身定位昂貴，記憶卡自然成為「懂的人才會買」的配件。

時至今日，NEOGEO記憶卡在復古市場與收藏圈中反而更受重視。一方面是其功能在當年極具開創性，另一方面則是原廠卡片數量有限，加上電池老化導致完品保存不易，使得狀態良好的原廠SNK記憶卡具有一定收藏價值。市面上也出現不少第三方重製或改用非揮發性記憶體的替代方案，解決電池壽命問題，但在情感與收藏層面，仍無法完全取代原廠產品的歷史地位。

整體來說，SNK NEO GEO記憶卡不只是一項單純的儲存配件，它象徵的是SNK對街機文化的延伸，以及對玩家成就與體驗連續性的尊重。即便在今日回頭看，它依然是遊戲硬體史上相當獨特、且極具代表性的設計之一。

The SNK NEO GEO Memory Card is one of the most iconic accessories in the NEOGEO ecosystem, and its design philosophy clearly reflects SNK’s forward-thinking vision in the early 1990s of creating a seamless bridge between arcade and home gaming. This small card played a crucial role as a portable save medium, allowing players to carry their game progress and high scores from arcade machines to home consoles, or vice versa. At a time when most games were bound to a single machine, this concept was both rare and remarkably advanced.

NEOGEO home consoles (AES) and certain MVS arcade cabinets support JEIDA V3 memory cards. As long as the same game is running on the system, players can insert the card to load saved data or high scores and continue playing. This feature was especially appealing to competitive and hardcore players, as it preserved the arcade culture of long-term mastery and achievement beyond a single session or location.

At the system level, the NEOGEO SP-S2 system ROM (and likely other system ROM versions as well) supports memory card capacities ranging from 2KiB to 16KiB in 2KiB increments. Regardless of capacity, games are required to access the card through the system ROM’s CARD calls rather than directly manipulating memory addresses, as direct access risks data corruption. This design choice shows that SNK had already considered compatibility and data safety across cards of different sizes and electrical characteristics.

In terms of hardware types, NEOGEO memory cards exist in several variants, including 8-bit wide, 16-bit wide, doubled 16-bit, and so-called “SNK ROM” cards. The most common and officially released SNK cards are typically 8-bit wide. Although only the lower byte is used for data, all accesses must still be performed as 16-bit word operations due to the 68000 processor bus design and the /UDS signal requirement. This is a hardware-level constraint rather than a software choice.

The original SNK-branded memory card uses battery-backed SRAM with a capacity of 2KiB. Internally, it relies on an LH5116 SRAM chip combined with voltage-switching circuitry to preserve data. Because the backup battery is not rechargeable, data loss becomes a real risk once the voltage drops below roughly 2V. This differs from the rechargeable backup battery found inside MVS cabinets and is one of the most common issues encountered by modern users of original cards. When the battery ages, replacement is the only solution to prevent permanent data loss.

There are at least two known official versions of the SNK Memory Card, each with a different circuit board design. Earlier versions use a board labeled C10075-X2-2, while later releases adopt the EZ866 board. Although their internal layouts differ slightly, functionality and compatibility remain essentially the same. Today, these variations are of particular interest to collectors, as they help identify production periods and revisions.

For the NEOGEO CD system, SNK chose a different approach. Instead of relying on an external card, CD systems include a built-in “virtual” memory card in the form of an 8KiB battery-backed SRAM chip. This integrated solution offers greater convenience and avoids issues such as card loss or external battery failure, but it also sacrifices the unique portability that allowed players to move data freely between different systems.

In terms of data structure, all NEOGEO memory cards share the same basic format regardless of capacity; only the size of each region differs. Data is organized into 64-byte units known as “blocks,” with the first block always reserved as a header. For example, a 2KiB card can store 31 usable data blocks. Since the JEIDA data bus is 16-bit wide, developers accessing 8-bit cards directly must take care to double addresses appropriately, or errors may occur.

From a market perspective, the NEOGEO Memory Card was always a niche but highly symbolic product. For casual players, it was not essential, as most arcade games were designed for short, intense play sessions. However, for high-score chasers, fighting game enthusiasts, and players who regularly moved between arcade cabinets and home consoles, the card offered exceptional value. Given the already premium pricing of NEOGEO hardware and software, the memory card naturally became an accessory aimed at knowledgeable and dedicated users.

Today, the NEOGEO Memory Card has gained renewed attention in the retro gaming and collector markets. Its pioneering functionality and limited original supply, combined with the difficulty of preserving battery-backed SRAM over decades, have given well-maintained original cards notable collectible value. Although many third-party alternatives now exist—often using non-volatile memory to eliminate battery issues—these replacements cannot fully replicate the historical significance and emotional appeal of the original SNK product.

Overall, the SNK NEO GEO Memory Card is far more than a simple storage accessory. It represents SNK’s commitment to extending arcade culture beyond the cabinet and respecting player progress and achievement across platforms. Even by modern standards, it remains a uniquely innovative and highly representative piece of gaming hardware history.