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Access time is the amount of time that passes between a request for data and when the data is provided. There are many other terms that refer to access time such as memory latency and seek time. These terms are different for various mediums.
One of the most common types of access time referred to is memory latency. This refers to the amount of time it takes for a memory controller to access and prepare an area of memory for output. This is an extremely important type of latency since it is often the determining factor in how fast programs may run on a system.
Another well-known type of access time is referred to as network latency. This type of latency refers to the amount of time required for a packet of information to travel from one point in a network to another. In terms of Internet access, this time can vary significantly depending on where the packet is being sent. For example, the network latency of sending a packet to a computer on the same physical network may be 15 milliseconds, while it may be several seconds when sent to a computer located in a distant country.
Hard drives and optical disk drives have several different types of latency. The first is known as rotational delay. Both hard drives and optical disk drives spin. The rotational delay is the time required for the disk to spin into a position where the read/write head can access the data.
The second type of latency in these types of systems is known as seek time. Once the disk has spun to the correct position, the read/write head must then move into the correct position for reading the data. The time these two processes take is variable and depends on how far from the original position the new position is located.
The final type of latency is known as the transfer time. This is how long the process of transferring information off the drive takes. This access time is different for various types of drives and is referred to as the bit rate.
With many variables tied to the latency of hard drives and optical disk drives, it can be difficult to determine the actual access time for a given drive. Drives are often advertised by their fastest speeds. This count often solely refers to the bit rate of the drive.
@Logicfest -- one thing that is intriguing is how technology improvements have often been targeted at reducing latency. Take the 1980s, for example, when it was common to have operating systems and even dictionaries for word processors stored on floppy drives. Those methods were effective, but offered very slow access times. The response was to make it standard to load both on hard drives and it is now common to see operating systems stored on fast, solid state drives.
This entire article describes something that has frustrated computer users since the devices were invented -- latency (when you hear people complaining about bottlenecks when it comes to computers and networks, they're really talking about latency). One of the cheapest ways to clear up latency issues is to install more RAM. Quite often, manufacturers don't fill motherboards with as much memory as they can hold and the computer can access due to price concerns. It doesn't cost much to double the amount of RAM you have and the performance boost will, in most cases, be very noticeable.
Another technique that is being more widely adopted is the use of solid state drives in conjunction with or in addition to standard hard drives. Solid state drives, by their very design, offer much faster access speeds than traditional, physical hard drives.