Dwight Elvey <elvey(a)hal.com> wrote: Hi I think we should clarify for Doug how you access Bubbles. These are not like standard read/write memory. You have to treat them more like a disk drive. The memory is organized into a number of loops. You can only see one location on each loop at any one time. This means that they are serial devices. To access all of the bits on the loop, you have to clock the chip with external magnetic fields to cause the bubble bits to rotate around the rings. Think of it as being something like a loop of paper tape in a tape reader. You can read anything but only one location at a time. To run the coils takes quite a bit of energy. Making the multi-phase clocks with drivers is tricky even by todays standards. Originally, Intel made some VMOS driver chips that were used with these bubble memories. This is partly why Intel gave them up. They still had a lot on Mil applications because they are considered to be non-volatile like core. Too much power and they could see the end of density increases. Dwight