Memory is a critical component of the computer, and computers would not function without it. Memory is also one of the essential parts of the computer because it allows quick access to information that can be used at any given time.
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The Memory Hierarchy
We have already discussed how a computer stores data using memory devices. This section will learn about the different types of memory available in a computer system and the hierarchy used to organize these memories.
When we talk about memories in a computer system, we refer to all the different storage devices used by the system. This includes everything from the small cache memories built into the CPU to the hard disk drives that store all our music and photos.
Computer systems use a hierarchy of memories, each level providing different benefits in terms of speed, capacity, and cost. This hierarchy is often referred to as The Memory Hierarchy.
Cache memory is a storage type used to hold frequently accessed data. It is usually located on the CPU or main memory chip and is used to store instructions and data that the CPU needs to access quickly. Cache memory is crucial because it can help the CPU to operate more efficiently by reducing the number of reads and writes it needs to perform.
Cache memory is divided into two types: L1 and L2. The L1 cache is responsible for holding data that the CPU is currently working with, while the L2 store carries data that the CPU may need in the future. Both cache types are essential, but the L1 cache is generally considered more critical because it has a shorter access time.
Every computer has some form of main memory. It is the place where data is held temporarily during processing. Main memory is often confused with storage (or secondary memory), where information is permanently stored. Storage devices include hard disks, CD and DVD drives, and USB memory sticks.
Operating systems and hardware devices use several different concepts when it comes to memory. These concepts include address space, paging, segmentation, caching, and virtual memory. You will reencounter these concepts in more detail when we discuss how operating systems work. But, let’s take a brief look at each one.
Address space is the total amount of addressable memory a given system has. Addressable means that the system can access a particular location in memory (i.e., it knows where it is). How much addressable memory a system has depends on the system’s architecture – for example, a 32-bit system can address 2^32 bytes of memory (4 gigabytes). In contrast, a 64-bit system can address 2^64 bytes of memory (17 billion gigabytes!).
Paging is a method of breaking up data blocks into fixed-size pages that can be stored in main memory or storage devices. For example, if we have 1 kilobyte (1024 bytes) of pages, then a 32-megabyte file would be stored as 32000 pages! When the computer needs to access data from the file, it will first look in the main memory to see if the page containing the required data is already there. If it isn’t, the carrier will be brought into the main memory from storage before being accessed.
Segmentation is similar to paging, except that instead of breaking up data blocks into fixed-size pages, we break them up into variable-size segments that correspond to logical divisions within the file (e.g., executable code, global variables, etc.).
Caching involves keeping copies of frequently accessed data in readily accessible locations to retrieve it when needed quickly. This process is known as caching because we effectively create a cache of frequently accessed data. Supplies are often used for both primary memory and storage devices – for example; many computers have a collection of frequently accessed disk sectors stored in main memory so that they don’t have to keep reading from disk every time they need them!
Virtual memory is a technique used by most modern operating systems that allows a computer to store more information than would fit physically in its main memory. It does this by using a combination of physical memory and space on disk. When the computer needs to remember something but does not have enough room, it uses virtual memory.
In computer systems, memory management controls and coordinates the use of memory by multiple programs and devices. Memory management is an essential part of any operating system.
Memory management is responsible for managing the computer’s memory. This includes the computer’s storage, including both physical memory (RAM) and virtual memory (on the hard disk or other storage devices).
Memory management is a complex task, and several concepts and terms are associated with it. Some of the more important ones are discussed below.
Storage: This refers to all places where data can be stored, including physical and virtual repositories.
Operating systems: An operating system is a type of software that manages the resources of a computer, including its memory. All computers have an operating system, and this is what allows you to run multiple programs and devices at the same time.
Hardware: This term refers to all of the physical parts of a computer, including its memory.
Computer devices: A device is anything that can store or retrieve data from a computer’s memory. This includes both hardware and software devices.
Storage is a critical part of any operating system or computer. Data storage hardware and software concepts are essential for any computer user or administrator to understand. This Basic Computer Concepts Siyavula moment introduces you to some critical hardware and software related to memory and storage.
One of the most important concepts regarding storage in operating systems is memory protection. Siyavula takes a moment to explain the basics.
In computing, memory protection is a process that prevents unauthorized access to memory locations. The hardware usually enforces memory protection but can also be implemented in software.
Memory protection ensures that only authorized processes can access certain areas of memory. This prevents malicious programs from damaging or corrupting essential data. Memory protection is an important security measure in modern operating systems.
There are various methods of implementing memory protection, depending on the architecture of the computer and the operating system. However, the most common way is through the use of virtual memory.
Memory latency is the delay between the time when a computer asks for data from memory and the time when it receives that data. It is measured in time units, such as nanoseconds (billionths of a second).
-The speed of the storage devices (hard disk, SSD, etc.)
-The speed of the operating system and other software
-The speed of the computer’s hardware (processor, bus, etc.)
-The amount of traffic on the network between the computer and the storage devices
There are several ways to reduce memory latency, including:
-Using faster storage devices (SSD, NVMe, etc.)
-Using faster-operating systems and software
-Using faster hardware (processors, bus, etc.)
Memory bandwidth is the rate at which data can be read or written to a memory device. The term is usually used for RAM or ROM, the main types of memory used in most computers and other electronic devices.
The bandwidth of a given type of memory is determined by the width of its data path and the speed at which it can operate. The data path is the number of bits that can be transferred simultaneously; the rate measures how fast those bits can be moved.
For example, a typical personal computer may have a data path width of 64 bits and a RAM speed of 1600 MHz (megahertz), which gives it a bandwidth of 1600 MB/s (megabytes per second).
There are two main types of memory: storage and operating. Both are measured in bytes, with a byte being equivalent to eight bits.
Storage is where data and programs are kept when they’re not being used. Working memory, or RAM, is where data and programs are temporarily stored while the computer works with them.
Both kinds of memory are found in computer devices but work differently. Storage doesn’t need electric power to keep the data inside, so it can store information even when the device is turned off.
Working memory needs electric power, so it loses all the data inside it when the device is turned off. But working memory is much faster than storage, so it’s better for running programs and working with data.