Unformatted text preview: gram(s) the CPU is currently woi*king on?
The time to fetch and load data from this storage space into the CPU registers must also
be very small as compared to that for disk storage to reduce the speed mismatch problem
with the CPU speed. Every computer has such a storage space, which is known as
primary storage, main memory, or simply memory. It is a temporary storage area that is
built into the computer hardware and in which instructions and data of a program reside
mainly when the program is being executed by the CPU. Physically, this memory
consists of some chips either on the motherboard or on a small circuit board attached to
the motherboard of a computer system. This built-in memory allows the CPU to store and
retrieve data very quickly. The rate of fetching data from this memory is typically of the
order of 50 nanosecond/byte. Hence the rate of data fetching from the main memory is
about 100 times faster than that from a high-speed secondary storage like disk.
Storage Evaluation Criteria
Any storage unit of a computer system is characterized and evaluated based on the
1. Storage capacity. It is the amount of data that can be stored in the storage unit. A
large capacity is desired. As compared to secondary storage units, primary storage units
have less storage capacity.
2. Access time. This is the time required to locate and retrieve stored data from the
storage unit in response to a program instruction. A fast access time is preferred. As
compared to secondary storage units, primary storage units have faster access time.
3. Cost per bit of storage. This refers to the cost of a storage unit for a given storage
capacity. Obviously, a lower cost is desirable. As compared to secondary storage units,
primary storage units have higher cost per bit of storage.
4. Volatile. If the storage unit can retain the data stored in it even when the power is
turned off or interrupted, it is called non-volatile storage. On the other hand, if the data
stored are lost when the power is turned off or in...
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This document was uploaded on 04/07/2014.
- Spring '14