BUBBLE MEMORYMAGNETIC CORE NVRAM
MEMORYIn computing, memory refers to the computer hardware devices used to store information for immediate use in a computer.
Eg. DRAM, SRAM.Non-volatile memory
Eg. Bubble memory, magnetic core memory and NVRAM.
Volatile memory is computer memory that requires power to maintain the stored information. Eg. magnetic core memoryNon-volatile memory is computer memory that can retain the stored information even when not powered. Eg. Bubble memory and NVRAM.
Magnetic Bubble Memory Description Magnetic bubble memory technology was introduced by Bell Telephone Laboratories in 1967.
Small cylindrical magnetic domains, which are called magnetic bubbles
The presence or absence of a bubble in a bit position is used to define the logic state.
Since the diameter of a bubble is so small (as little as a tenth of a micrometer), many thousands of data bits can be stored in a signle bubble-memory chip.
In the spring of 1977 Texas Instruments was the first to market a 92,304-bit (11.25kb approx) bubble memory.
Ferromagnetism vs. orthomagnetism
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.
The orthomagnetic sheet in bubble memory-orthomagnetic axis os perpendicular to the square surface
-uniaxial magnetic property
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.
Squeezing the bubbles down in size
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
Moving the bubbles using external magnetic fieldsPUSHPULL
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
Driving coils and guide patternssteady rotating magnetic field
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.
Different guidance patterns
This image shows two possible patterns for the magnetic guide pieces in magnetic bubble memory
Bubbles moving in the T-I-style pattern
This animation shows how magnetic domains propagate through a pattern of T- and I-shaped guide pieces
Bubbles moving in the V-style pattern
This animation shows how magnetic domains propagate through a pattern of V-shaped guide pieces
It is conceptually a stationary disk with spinning bits.
In order to read or write the bubbles, they are rotated past the equivalent of a read/write head.
Data is retained even when power is no longer applied to the chip.
Solid-state technology ( no moving parts)they have higher reliability than tape or disc storage no preventive maintenance.
Small and lightweight
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 applicationsSlow access. A lagre bubble memory would require large loops, so accessing a bit require cycling through a huge number of other bits first.
MAGNETIC CORE MEMORY
What is magnetic core memory?Magnetic core memory,is an early form of random access computer memory.
It uses small magnetic ceramic rings,the cores,through which wires are threaded to store information via the polarity of the magnetic field they contain.
How core memory works?
To read a bit of core memory, the circuitry tries to flip the bit to the polarity assigned to the 0 state, by driving the selected X and Y lines that intersect at that core.
If the bit was already 0, the physical state of the core is unaffected.
If the bit was previously 1, then the core changes magnetic polarity. This change, after a delay, induces a voltage pulse into the Sense line.
The detection of such a pulse means that the bit had most recently contained a 1. Absence of the pulse means that the bit had contained a 0. The delay in sensing the voltage pulse is called the access time of the core memory.
Following any such read, the bit contains a 0. This illustrates why a core memory access is called a destructive read: Any operation that reads the contents of a core erases those contents, and they must immediately be recreated.
WritingTo write a bit of core memory, the circuitry assumes there has been a read operation and the bit is in the 0 state.
To write a 1 bit, the selected X and Y lines are driven, with current in the opposite direction as for the read operation. As with the read, the core at the intersection of the X and Y lines changes magnetic polarity.
To write a 0 bit (in other words, to inhibit the writing of a 1 bit), the same amount of current is also sent through the Inhibit line. This reduces the net current flowing through the respective core to half the select current, inhibiting change of polarity.
The access time plus the time to rewrite is the memory cycle time.
The Sense wire is used only during the read, and the Inhibit wire is used only during the write. For this reason, later core systems combined the two into a single wire, and used circuitry in the memory controller to switch the function of the wire.
Advantages:It was more cost effective than high performance vacuum tube or transistor memory.
Better performance than low cost drum memory.
It is non-volatile in nature.
The components had a higher life time expectancy and their operating characteristics do not alter over time.
DisadvantagesMagnetic core memory has been replaced by semiconductor memory because each integrated circuit in semiconductor memory contains thousands of semiconductor devices which represents millions of bit.
Magnetic core memory dont get smaller than that required by simple calculator.
Reading a bit from a core sets its state to zero which is a term of destructive reading which needs a write cycle to restore the previous bit.
NVRAM Non-volatile random-access memory(NVRAM) is random-access memorythat retains its information when power is turned off.
The NVRAM is a small 24 pin DIP (Dual Inline Package) integrated circuit chip and is thus able to obtain the power needed to keep it running from the battery installed in your motherboard.
NVRAM is also in your computer monitor,printers, cars, smart cards, and other devices that require remembered settings
Types of NVRAMSRAM (Static Random Access Memory): It is made non-volatile by connecting it to a constant power source such as a battery. Since SRAM requires continual power supply in order to maintain its data, an NVRAM that is made from an SRAM will need to use an available power supply to make sure it continues working.
Ferroelectric RAM,FeRAM orF-RAMandMagneto resistive RAMorMRAMare also types of NVRAM used for various applications.
Advantages of NVRAMProvides excellent performance when compared to other non-volatile memory products
Supports applications that need quick read or write operations using non-volatile memories, such as antilock braking systems and parallel processing controllers for local area networks.
Less power is required for NVRAMs, so the backup guarantee can be ensured for up to 10 years.
Disadvantage of NVRAMIf the battery embedded in the NVRAM chip fails, then this means that your system clock will stop running and important system configuration information may not be maintained.Lower storage densityOverall capacity limitationHigher cost
THANK YOU!SPECIAL MENTION,PROF. KASHYAP JOSHI
Volatile memory is computer memory that requires power to maintain the stored information. Eg. magnetic core memoryNon-volatile memory is computer memory that can retain the stored information even when not powered. Eg. Bubble memory and NVRAM.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.This image shows the orthomagnetic "sheet" used in