> There are also 255 representations of almost all representable numbers. For example, 10 is 1 x 10^1 or 10 x 10^0 – or any one of 253 other representations.
You are not correct. The smallest significand possible is 1x10^1, but you can't delve further into positive exponents. Conversely, 56 signed bits allows the largest integer power of 10 as 10 000 000 000 000 000 so the exponent will be -15. So there are exactly 17 representations of 10, and that's the worst it gets. All other numbers except powers of 10 have fewer representations, and most real world data affected by noise has a single representation because they use the full precision of the significand, and you can't shift them to the right or left without overflow or loss of precision.
So the redundancy is much less than you think, one in 10 real values has two representations, one in 100 has three etc. This is common for other decimal formats and not that big of a problem, detecting zero is a simple NOR gate on all significant bits.
The real problem with this format is the very high price in hardware (changing the exponent requires recomputing the significand) and complete unsuitability for any kind of numerical problem or scientific number crunching. Because designing a floating point format takes numerical scientists and hardware designers, not assembly programmers and language designers.
Heck, the only reason he put the exponent in the lower byte and not the upper byte, where it would have ensured a perfect compatibility to most positive integers, is that X64 assembly does not allow direct access to the upper byte.
