No manufacturer will ever release yield data unless they have to for some reason. It's considered a trade secret. So- to answer your question directly, no- it isn't advertised in the industry.
However, there are many engineers whose jobs are to improve the line throughput and end-of-line yield. This often consists of using techniques like binning and block redundancy to make losses off the line function enough to be saleable. Block redundancy is certainly used today. It's pretty easy to analyze:
(failed blocks per part)/(blocks per part)*(failed blocks per part)/(blocks per part)
That'll get you the probability of both parallel blocks failing. I'd doubt you'd end up with a yield as low as 70%, as typically 90% is the minimum acceptable yield.
Not usually. To read 8 bits, normal practice is to read one bit from each of 8 separate DRAMs.
However, if you were forced by cost or power considerations to use a single device, DRAMs of that era provided both burst mode and page mode, which allow you to provide the column number of the first bit you need, then automatically access adjacent bits in succeeding cycles - in page mode, up to all 256 bits in the currently open row.
(64k DRAMs are well over 25 years old! Where exactly is this question being dug up from - is this an archaeology question?)
The details of page and burst modes differ, and when L1/L2 caches became universal, burst modes evolved to address entire cache lines, wrapping the column address round by modular arithmetic rather than strictly ascending.
Page mode also allowed convenient shortcuts to designers of video cards of that timeframe (25 to maybe 15 years ago).
However, in newer DRAM designs, (the first DDR generation) page mode has quietly been dropped, leaving burst modes so you may have to address every eighth column individually at precisely the right time if you need larger groups of adjacent locations. This makes life more difficult if you're using DRAM without a cache/CPU combination, for example in FPGA applications.
Best Answer
Each "logical" column is actually implemented using multiple physical columns on the chip. When you ask for a burst transfer, the physical memory array inside the chip performs a single cycle, transferring, say, 64 bits all at once. Those bits will be serialized as 8 bytes over the external 8-bit bus in a DDR burst using 4 clock cycles.
Does this help?