On Wednesday, September 4, 2019, 10:15:00 PM PDT, \0xDynamite
   <dreamingforward@gmail.com> wrote:

   >  The industry developed UV-erasable EPROM as a substitute, which
   allowed
   > only the erasure of the entire memory chip, , and some early EEPROM.
   > (Electrically erasable programmable Read-Only-Memory).Eventually
   > "flash-EPROM" was developed.  [1]Flash memory




                             Flash memory

   Flash memory is an electronic (solid-state) non-volatile computer
           storage medium that can be electrically erased...

   >Ah, I hadn't made the connection between FLASH drives and Flash
   EEPROMS.  However,  this pushes the question back:  how would an
   EEPROM do it?  Old PROMs used to burn fuses to maintain state, but how
   to restore state, eh?
   >I believe that one could make flash drives that start at all-1s and
   then burn the 0s into the memory.  A small battery-powered device
   could maintain the address of the next writable word, otherwise once
   the device reached the end of memory, it would no longer be useful
   for. writing.
   These devices injected a tiny electric charge into a "floating gate",
   an otherwise-insulated conductor surrounded by an extremely good
   insulator.
   [2]https://en.wikipedia.org/wiki/Floating-gate_MOSFET
   The level of insulation required was phenomenal:  In order to store a
   bit of data for many decades, an effective resistance of over 10*20
   ohms would have been necessary.   If you assume a capacitance of one
   picofarad (10E(-12) farads) in parallel with 10**20 ohms, that's a time
   constant of 10**8 seconds, or 3 years.
   Erasing an EPROM with UV light activated electrons into 'conduction
   bands' that would not ordinarily be populated, and thus erase the
   entire device.
   The first EPROM I ever heard of was the Intel 1702 2 kilobit  (256 by 8
   bits) device, of which I used one:  As the program store of the
   "Dyna-Micro" single-board computer that I built in 1977.  It was
   extremely difficult to program, requiring very high voltages.  The next
   EPROM I used was a 2708 device, which was far easier to program.
             Jim Bell

References

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   1. https://en.wikipedia.org/wiki/Flash_memory
   2. https://en.wikipedia.org/wiki/Floating-gate_MOSFET

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   4. https://en.wikipedia.org/wiki/Flash_memory