Knowing Your Computer: Types of Memory

All computers require memory to operate. The main computer memory is Random Access Memory, or RAM for short. It is called this because the data contained in it can be accessed in any, or random, order. It is produced on small circuit boards in the form of sticks, which are often referred to as sticks of memory. Information is stored in the memory as it awaits being processed by the central processing unit, or CPU. It is essential to have the right type and speed of memory to ensure your system is operating optimally.

Knowing Your Computer: Types of Memory

Knowing Your Computer: Types of Memory

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Knowing Your Computer: Types of Memory

Knowing Your Computer: Types of Memory

The main type of memory used today in desktop computer systems is Synchronous Dynamic RAM (SDRAM). With in the past several years, Double Data Rate SDRAM (DDR SDRAM, or simply DDR) has become the standard for most systems, with older memory now being referred to as Single Data Rate (SDR SDRAM). Occasionally, systems use Rambus Dynamic RAM (RDRAM) or DDR2 RAM, which are slightly different and are outside of the scope of this article.

SDRAM is different from other forms of asynchronous memory because it waits for each clock, or computing cycle, before it responds to inputs. These clocks happen very fast in computers (millions of times a second) but still the speed of the memory is ultimately limited by the computer bus. This is the wiring on the main- or motherboard in the system that connects all the components. The processor and memory can both handle high clock speeds, but if the speed of the system bus is low, they will be limited by the lowest speed. It is important that they all operate at similar speeds to operate most efficiently. For example, SDR SDRAM comes in PC66, PC100 and PC133; these numbers refer to the clock speed of the RAM in megahertz (a million cycles a second): 66 MHz, 100 MHz and so forth. If the system bus speed is rated at 100 MHz and the memory at 66 MHz, then the memory isn't operating as quickly as it could and PC100 memory should be purchased. Of course, if PC133 were purchased for this same system, the extra 33 MHz would simply be wasted because the system bus can only handle 100 MHz.

Double Data Rate (DDR) memory is very similar to traditional SDRAM except it transfers data twice during each clock cycle. This doubles the transfer rate of the memory while the system bus stays the same. So a 100 MHz system bus that handles DDR memory can effectively use 200 MHz RAM. DDR comes in many speeds, each with two designations. On the box or somewhere in the specifications, the memory will be referred to as DDR-xxx, where the xxx is replaced by the effective clock speed of the memory, such as 200 as in the previous example. It will also list a PC-xxxx number, where xxxx represents the bandwidth of the entire stick of memory. This is not particularly important to understand for novices. The most common are: DDR-200/PC-1600, which operates at a clock speed of 100 MHz (effectively 200 MHz), DDR-266/PC-2100, which operates at 133 MHz (effectively 266 MHz), DDR-333/PC-2700, operating at 166 MHz (333 MHz) and DDR-400/PC-3200, which operates at 200 MHz (400 MHz).

It is very important to know which type (SDR or DDR SDRAM) and speed of memory your system uses and to always purchase this type when upgrading or replacing your memory. You can usually find this information in the manual or contact the manufacturer.

Knowing Your Computer: Types of Memory

Basic Computer Features 101

When buying a desktop computer is one of the first things to look at will be its use and individual budget. For example, a machine that will be primarily used for gaming should focus on lots of memory, a powerful processor, enhanced video and graphics, while a computer that will be used for Internet browsing and simple word processing will not need nearly as much frills. This computer-buying guide covers the basics to give you some idea of the important features to look at.

Basic Computer Features 101

Basic Computer Features 101

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Basic Computer Features 101

Basic Computer Features 101

CPU

CPU stands for central processing unit and is the brains of the computer. It is where most of the actual computing takes place and the quality of the processor will greatly determine the performance of the computer. The processorspeed is measured in GHz.

There are budget processors, mid grade and high-end processors. The high end ones maybe necessary for enhanced computer functions, such as gaming and entertainment, but overall the mid grade types are quite good and will deliver great performance for most any uses. Overall the two best brand names for processors are Intel and AMD.

RAM Memory

RAM memory is used to run programs on the computer and the more RAM you have, the better the performance and speed of computing and to avoid slow downs and crashes. Gaming and entertainment need a lot more RAM than regular computer tasks for which 1 GB is usually sufficient, but 2 GB is really great. At least 3 GB, is optimal for gaming and mediaexperiences.

Also, it is a good idea to check and make sure that there are open memory upgrade slots so you can always add more memory as it is fairly cheap and easy to install.

Hard Drives

Hard drives are significant for the speed capacity of computers. Overall, the larger the drive, the more storage space and the faster the computer. Optimal is 500 GB.

Optical Drives-CD/DVD/Blu-ray

Most computers these days come with DVD/CD burners, and even if they do not they are cheap and easy to install and come in internal and external versions. Blu-ray is the latest option for burning in high definition format.

External Ports and Connections

Ports are used to attachperipherals, such as printers, Internet, iPods and others. Most important will be to have at least 5 USB ports, one FireWire port as well as an Ethernet connection for Internet and networking. Overall, the more ports you have the more variety and options will be available to add ons.

Monitors

A good monitor is essential for a quality computer experience. The older CRT models have become largely obsolete with the introduction of the LCD screen monitors, however many people still use them and they can still be found at online shopping sites. LCD screen monitors have a superior display with a reduced size due to the flat panel and their lower power consumption over the CRT models.

Basic Computer Features 101

Different Types of Human Memory

The process whereby memories are forged into the mental system is a remarkable one that is often misunderstood. But by studying the nature of memory, we gain a higher insight in to the intricate workings of this most vital aspect of the human brain. Some compare the human memory to a tape recorder-yet it is not so simple. While memory can serve as a retainer for key data that we want to "re-play" over and over again, it is a more dynamic and complex mechanism. In addition to storing information, it also allows us to recall feelings, sensations, images, as well as carry out basic functions such as talking.

Different Types of Human Memory

Different Types of Human Memory

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Different Types of Human Memory

Different Types of Human Memory

Since human memory is such a complex system, it cannot be nailed down to an exact science. In fact, cognitive psychologists working in thefield of memory often have disagreements. What has been established is that there are three main types of human memory – sensory, short term and long term-plus a fourth related faculty called the working memory.

When we speak of "sensory memory", "we are referring to the few split seconds that follows the initial perception of an object. If you are able to briefly look at something and immediately memorize its details, then that is an instance of sensory memory. Usually, in these cases, when you are only able to see something for a few split seconds, you might feel like you saw a lot more than you are able to describe.

Some of the data that is perceived in a sensory memory will subsequently be transferred to a short term> memory. We call short term memory the ability to recall something from several seconds to a minute ago.

There is also a type of memory that is referred to as working memory. It can be viewed as a form of short term memory, in that it refers to the limited store that is needed in order for certain mental tasks to be performed. Whereas short term memory is rooted in duration, working memory is defined by purpose. Baddeley's Model of Working Memory defines three components to this type of memory -the verbal store, the Visual-spatial sketchpad, and the central executive, which determines control and rehearsal.

Finally, there is long term memory. Unlike short term and sensory memories, which disappear in abrief amount of time, long term refers to memories that can be stored for a period of up to several years. Psychologists disagree on how long term memory works. Some argue that a long term memory remains in the brain forever, but this is impossible to prove, as there has never been a human being who has lived forever!

While it was once thought that there was no real determining factor between what made in short term memory and a long term one, research has since established that the brain contains numerous systems of memory and that information is constantly being transferred among these various systems. Hence, the ongoing research in to the mysterious nature of how memory works.

Different Types of Human Memory