Digital Designing, Types of memory

1. Volatile memory is computer memory that requires
power to maintain the stored information. Eg. magnetic
core memory
Non-volatile memory is computer memory that can
retain the stored information even when not powered.
Eg. Bubble memory and NVRAM.

2. This image demonstrates the difference between "ordinary" ferromagnetic
materials (above), and orthomagnetic materials (below): The latter only form
magnetic poles (indicated on the samples by red/white color gradient) if the
external field provided by the big magnet poles at left and right is aligned with the
orthomagnetic axis, as indicated by the little black arrows.

3. This image shows the orthomagnetic "sheet" used in magnetic bubble memory; it
has its orthomagnetic axis perpendicular to the square surface. Even without an
external field, it tends to form these sharply divided areas, some with north pole
up/south pole down, others with the poles the other way around. The term
describing this property is uniaxial magnetic anisotropy.

4. This image shows how one kind of domain in the orthomagnetic sheet of magnetic
bubble memory grows and the other shrinks, as an external magnetic field (the big
magnet poles) is imposed on them

5. This image shows how external fields (symbolized by small magnets left and right)
working at an angle can "push" and "pull" domains, or "bubbles" in the
orthomagnetic sheet of a magnetic bubble element

6. This image shows the setup of driver coils and guide pieces around and on the
orthomagnetic sheet of a magnetic bubble memory. The coils together form a
steadily rotating magnetic field along the surface of the sheet. Since the guides are
ferromagnetic, they assume magnetic poles when magnetized by the coils, which
in turn "coerces" the domains along the guide pattern.

7. This image shows two possible patterns for the magnetic guide pieces in magnetic
bubble memory

8. This animation shows how magnetic domains propagate through a pattern of T-
and I-shaped guide pieces

9. This animation shows how magnetic domains propagate through a pattern of V-
shaped guide pieces

10. This bubble memory is much like magnetic tape or magnetic disc
memory storage in that it is nonvolatile meaning that the data is
retained even when power is no longer applied to the chip.
Since bubble memories are a product of solid-state technology (there
are no moving parts), they have higher reliability than tape or disc
storage and do not require any preventive maintenance.
In addition, the bubble memory is small and lightweight and is,
therefore, an excellent choice for compact designs and portable
applications
Slow access.
A lagre bubble memory would require large loops, so
accessing a bit require cycling through a huge number of other bits