Magnetic core memory Part 2
RAID Recovery - Magnetic core memory
Read and Write Process
Reading in magnetic core memory happens when the bit in question attains a ‘0’ status. This is done by driving the selected X and Y lines in the direction that causes the core to flip to the polarity which the machine considers zero. If the core was already in 0 state, no flip will occur. In ‘1’ state, the core will undergo a flip. When this happens a small current pulse will be induced to the Sense line to indicate that the memory location used to hold a ‘1.’ If no pulse is seen, it indicates that the core has already been in the ‘0’ state.
In the writing operation, the flip occurs from 0 to 1. For this, the current in the X and Y lines in question goes in the opposite direction which it did in the read operation. If the core is to hold zero, the same amount of current as used in the X and Y lines is sent to the Inhibit line. As a result, the combined field from the X, Y and Inhibit lines reduces to half of the field needed to flip the core. Thus it results in the 0 state of the core.
Summary: Magnetic core memory is an earlier form of non-volatile memory. It consisted of ferrite ceramic rings called the cores, held together in a grid structure. The read/write process is carried out by changing the polarity of the magnetic field of the core.
