[nephrite]

They just reimplemented floating point with bigger mantissa and exponent. Rounding erorrs will appear with sufficiently large/small numbers.

[ncruces]

Actually, the exponent is smaller. IEEE 754 64-bit binary floats have an 11 bit exponent, 1 sign bit, and 53 bit mantissa (one of the bits of the mantissa is implied, by actually knowing what they're doing, rather than… whatever this is).