Dreamcast third-party Visual Memory Units
From Sega Retro
The Sega Dreamcast's Visual Memory Units are an interesting peripheral, but as memory cards they have several flaws. The built in-screen made them comparitively more expensive than memory cards found on rival consoles such as the PlayStation, and because of its design, a VMU is limited to about 128kB (1Mb) of storage - 200 "blocks" in Dreamcast terms.
Considering the original PlayStation matched this storage space in 1994, and the PlayStation 2 could offer a whopping 4MB (32 times more memory than a VMU) for less money, it was often considered a wiser idea to go down the third-party route, investing in memory cards which lack the VMU's exclusive features, but are significantly cheaper as a result. There are other reasons for this too - having a memory unit with a screen in the second controller port in a Dreamcast controller is a pointless exercise, as you'll not be able to see it, and cards without screens don't require their own batteries.
Dozens of memory cards were produced for the Dreamcast, usually 128kB (1Mb; 200 blocks), 256kB (2Mb; 400 blocks) or 512kB (4MB; 800 blocks) in size. For cards larger than 128kB there is usually a switch to toggle between blocks of 200. Sega later produced their own Dreamcast 4x Memory Card in response to these ideas but these were not as widely released. The most notable card is the Massive Memory Card Plus which contains 1MB (8Mb; 800 blocks) of save game storage.
This page lists all of the memory cards we know about. It is likely incomplete.
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