-  Sega System E

A somewhat similar arcade board based on the Master system.
It uses 2 VDP, both identical to the Master system.
It is also equipped with 2 PSG (still mono), again same as Master System's tweaked PSG.
It has 16kb of RAM. It does not come with a CPU, games are expected to be packaged with their own.
Z80 CPUs are clocked slightly higher : 5.38 Mhz.

Exclusive games for it :
- Tetris
- Pythagoras no Nazo
- Slap Shooter

Apparently Tetris only makes use of 1 VDP.

FBA supports this board but we cannot borrow code from it due to the non-commercial clause.

-  Sord M5

Shares a lot of similarities with the SG-1000/SC-3000 :
Most of the differences bows down to the I/O ports and the BASIC ROM that comes with it.
This thing supports cartridges as well as tape games.
It would be nice to support at least cart games.

-  Memotech MTX

Same as Sord M5, a lot of similarities to the SC-3000.