Although it is several times more expensive, it does have advantages. It has now become an alternative mass storage device to the mechanical hard drives. With recent advances in flash memory technology that help improve write speed and also reduce cost, flash memory has gained its popularity in the form of the Solid State Drive (SSD). Interested in knowing more? Watch this video to learn how floating gate transistors and flash memory work. These ROMs are not strictly read-only, but can actually be erased and re-programmed, although with slow speed and often requiring special equipment. It has been used since the mid-80's in some types of read-only memory (ROM) to store the device's firmware that is unlikely to be changed or updated. The floating-gate transistor in flash memory has been around longer thank you may think. The main memory is designed to be randomly accessible, hence the name Random-Access Memory, or RAM (as opposed to a sequentially accessed medium such as a cassette tape). They reside in the computer’s main memory, waiting to be fetched by the CPU to process.
Your running application generally comprises millions of instructions, and the data to be processed can be many times more. But how does it know what to copy? It has help from a sophisticated bit of hardware called the prefetcher, which does a good job of guessing the content needed for that CPU. Cache contains a partial copy of instructions and data from the main memory that is likely to be processed in the near future. They are not task specific and they can be randomly-accessed. Without a cache memory, a fast CPU could waste most of its time waiting for data from the slower main memory, causing your device to become very slow. Cache is the internal memory pool of a CPU, made from flip-flops similar to those of the internal registers with the main differences being that the cache is much larger. After each operation, the content in these registers gets replaced by the next set of instructions and data from a larger memory pool within the CPU, called the cache memory. A CPU only has a handful of registers, and they are task specific: their purpose is either to hold numbers or instructions to manipulate those numbers. They are the fastest, most frequently used type of memory, made from a group of fundamental memory circuits called flip-flops. The CPU uses internal registers to temporarily hold instructions and data for immediate processing. Memory hierarchy lets computer designers optimize their machine’s memory in an economical way by combining different types of memory into layers and choosing what data to store in each layer. Fast memory is usually small and expensive, while large and affordable memory is generally slow.
However, there is always a trilemma among speed, size and cost of the memory. We all want fast devices that can store large amounts of data, and for this we need a fast CPU with a large amount of fast memory to support it.
Watch this video to learn how a CPU works. These CPUs come in different designs, sizes and features, but their fundamental operations remain the same. It then performs basic arithmetic, logic, control and input/output operations specified by the instructions. The CPU fetches instructions from a program and data from the device's memory. Computers and digital devices, from smart phones to simple appliances, have a central processing unit, or CPU, that act as their brain.
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