Right, MAME fills the RAM with rand() which will be different to a real Delta-1. I don't think an SRAM chip will be 100% random at power-on, it will have a pattern. Maybe some of the bits are truly 'random' (with parameters: temperature, magnetic field, slight voltage differences, ...)

This addressing thing won't work on the real chesscomputer, it will put the ROM table before RAM:

remove:
map(0x2000, 0x20ff).mirror(0x1f00).ram(); // A13

add:
map(0x2bc0, 0x2bff).rom().region("maincpu", 0x0880);
map(0x2c00, 0x2cff).ram();