Sega Dreamcast 4x Memory Card (HKT-4100)

Summary

The Dreamcast 4x Memory Card (also Memory Card 4X) is pure flash memory for the Sega Dreamcast console to save game levels. Unlike the Sega Visual Memory Unit (VMU), this extension offers four times as much memory, but no display, screen and buttons, so it is not suitable for the mini-games. And while two VMUs can be paired, this is useless with the 4x Memory Card and does not work from the layout of the pins either. No batteries are necessary for this.

A VMU offers 128 KiB, 28 of which are reserved for the system, so that 100 KiB remain as memory. The 100 KiB in turn are divided into 512 byte blocks, which results in a total of 200 blocks. Since the Dreamcast can only address the memory in such portion sizes, the 4x Memory Card does not offer a large continuous memory, but four banks of 200 blocks each, is basically a collection of individual memory cards. On the 4x Memory Card there are four symbols and four small LEDs that signal the current active bank. After booting the console, Bank 1 is always active, which can quickly lead to a game not being able to save progress, because Bank 1 is full and you have forgotten to choose another bank before. Because in order to change the bank, the small button on the front of the memory card must be clicked as often as the bank number is.