Bubble Memory! It was started by Bell Labs although toward the end IBM was one of the last groups pushing it. In a way bubble memory is so simple. A strong m

Bubble Memory! It was started by Bell Labs although toward the end IBM was one of the last groups pushing it. In a way bubble memory is so simple. A strong magnetic field can "push around" magnetic domains on a piece of tape or whatever without flipping the bits if you get it just right. The two fundamental tricks that make it an engineering project that was successful for awhile are that its possible to build a thin film and some other components so stable and linear that you can push thousands, even millions of magnetic domains around without screwing them up, and superficially you would feel that electromagnetic stuff is all speed of light but moving magnetic domains can happen at just the right speed that you can read out a bubble memory using 1970s TTL logic, not too fast and not too slow. It was quite temperature sensitive like all magnetic things. It died as a technology because it only scaled over a factor of a thousand or so in an exciting computational era of changes much faster than now, where an order of magnitude only lasted a year or so at most. It couldn't have been done five years earlier, there was a very narrow window for it between TTL type logic finally being fast enough to read the bits as they flew by vs just a few years later simple static ram and eprom would store the same amount faster and simpler. It was kind of like a no-moving parts delay line that relied the speed of magnetic domain flipping being predictable repeatable and a useful speed. Bitsavers has some fun reads on ancient hardware technology. You can read IBM manuals as the technology was advancing, pretty interesting stuff. DEC also.