Types of USB October 3, 2009

Today just about every PC comes with Universal Serial Bus, or USB ports. In fact, many computers will even have additional USB ports located on the front of the tower, in additional to two standard USB ports at the back. In the late 1990s, a few computer manufacturers started including USB support in their new systems, but today USB has become a standard connection port for many devices such as keyboards, mice, joysticks and digital cameras to name but a few USB-enabled devices. USB is able to support and is supported by a large range of products.
Adding to the appeal of USB is that it is supported at the operating system level, and compared to alternative ports such as parallel or serial ports, USB is very user-friendly. When USB first started appearing in the marketplace, it was (and still is) referred to as a plug-and-play port because of its ease of use. Consumers without a lot of technical or hardware knowledge were able to easily connect USB devices to their computer. You no longer needed to turn the computer off to install the devices either. You simply plug them in and go. USB devices can also be used across multiple platforms. USB works on Windows and Mac, plus can be used with other operating systems, such as Linux, for example, with a reliable degree of success.

Before USB, connecting devices to your system was often a hassle. Modems and digital cameras were connected via the serial port which was quite slow, as only 1 bit is transmitted at a time through a serial port. While printers generally required a parallel printer port, which is able to receive more than one bit at a time — that is, it receives several bits in parallel. Most systems provided two serial ports and a parallel printer port. If you had several devices, unhooking one device and setting up the software and drivers to use another device could often be problematic for the user.

The introduction of USB ended many of the headaches associated with needing to use serial ports and parallel printer ports. USB offered consumers the option to connect up to 127 devices, either directly or through the use of a USB hub. It was much faster since USB supports data transfer rates of 12 Mbps for disk drives and other high-speed throughput and 1.5Mbps for devices that need less bandwidth. Additionally, consumers can literally plug almost any USB device into their computer, and Windows will detect it and automatically set-up the hardware settings for the device. Once that device has been installed you can remove it from your system and the next time you plug it in, Windows will automatically detect it.
Key Terms To Understanding USB
USB
Short for Universal Serial Bus, an external bus standard that supports data transfer rates of 12 Mbps.

USB 2.0
Also referred to as Hi-Speed USB, USB 2.0 is an external bus that supports data rates up to 480Mbps. USB 2.0 is an extension of USB 1.1.

USB OTG
Short for USB On-The-Go, an extension of the USB 2.0 specification for connecting peripheral devices to each other. USB OTG products can communicate with each other without the need to be connected to a PC.

More USB Related terms

plug-and-play
hot plugging
external data bus
port
serial port
data transfer rates
ultra wideband

USB 1x
First released in 1996, the original USB 1.0 standard offered data rates of 1.5 Mbps. The USB 1.1 standard followed with two data rates: 12 Mbps for devices such as disk drives that need high-speed throughput and 1.5 Mbps for devices such as joysticks that need much less bandwidth.

USB 2x
In 2002 a newer specification USB 2.0, also called Hi-Speed USB 2.0, was introduced. It increased the data transfer rate for PC to USB device to 480 Mbps, which is 40 times faster than the USB 1.1 specification. With the increased bandwidth, high throughput peripherals such as digital cameras, CD burners and video equipment could now be connected with USB. It also allowed for multiple high-speed devices to run simultaneously. Another important feature of USB 2.0 is that it supports Windows XP through Windows update.

USB OTG
USB On-the-Go (OTG) addresses the need for devices to communicate directly for mobile connectivity. USB OTG allows consumers to connect mobile devices without a PC. For example, USB OTG lets consumers plug their digital camera directly into a compliant printer and print directly from the camera, removing the need to go through the computer. Similarly, a PDA keyboard with a USB OTG interface can communicatea with any brand PDA that has a USB OTG interface.

USB-OTG also provides limited host capability to communicate with selected other USB peripherals, a small USB connector to fit the mobile form factor and low power features to preserve battery life. USB OTG is a supplement to the USB 2.0 specification.

Types of USB Connectors
Currently, there are four types of USB connectors: Type A, Type B, mini-A and mini-B and are supported by the different USB specifications (USB 1, USB 2 and USB-OTG).

USB A (Host)
Often referred to as the downstream connector, the Type A USB connector is rectangular in shape and is the one you use to plug into the CPU or USB hub.

 

 

USB B (Device)
Also called the upstream connector, the Type B USB connector is more box-shaped and is the end that attaches directly to the device (such as a printer or digital camera).

Local Storage/Remote Storage October 3, 2009

Local Storage

All threads of a process share its virtual address space. The local variables of a function are unique to each thread that runs the function. However, the static and global variables are shared by all threads in the process. With thread local storage (TLS), you can provide unique data for each thread that the process can access using a global index. One thread allocates the index, which can be used by the other threads to retrieve the unique data associated with the index.

The constant TLS_MINIMUM_AVAILABLE defines the minimum number of TLS indexes available in each process. This minimum is guaranteed to be at least 64 for all systems. The maximum number of indexes per process is 1,088.

When the threads are created, the system allocates an array of LPVOID values for TLS, which are initialized to NULL. Before an index can be used, it must be allocated by one of the threads. Each thread stores its data for a TLS index in a TLS slot in the array. If the data associated with an index will fit in an LPVOID value, you can store the data directly in the TLS slot. However, if you are using a large number of indexes in this way, it is better to allocate separate storage, consolidate the data, and minimize the number of TLS slots in use.

Remote Storage
The internet has revolutionized data security with remote backup services. This is a relatively new concept that allows personal computer users and businesses to store and backup essential data from multiple computers on an online server. These services offer secure and reliable offsite storage that will enable you to recover from unexpected system crashes and other disasters.

A remote backup service is a convenient backup system that is able to compliment traditional storage mediums such as CDs, DVDs, hard disks, flash drives, tapes and local backups. This type of service will protect your information and provide additional protection against the loss of data caused by viruses, other exploits and system errors. Online storage services offer an ideal, secure storage solution with numerous features, usually for an affordable price.

When it comes to the offsite storing and recovering of data, there are several available options. While many are effective, a remote online storage tends to be much faster and more reliable than others. These services include easy to use interfaces that can be accessed with passwords, along with drag and drop, data compression, data transfer and data encryption features.

During the process of data storage, most online companies provide the following:

• Automated data backups on scheduled intervals. This may be set on a daily, weekly or monthly basis

• Access to previous backups that have been stored on the remote server

• The ability to recover data lost or damaged from backups of previous versions stored on the remote server

Online Storage October 3, 2009

Storing or backing up data over the Internet. There are numerous third-party storage providers that offer this service.

May refer to disk drives, which are attached to the computer, either internally or externally, in contrast to “offline storage,” such as removable disk and tape cartridges.

Software file hosting
Authors of Shareware, Freeware and Open Source/Free software often use file hosting services to serve their software. The inherent problem with free downloads is the huge bandwidth cost. These hosts also offer additional services to the authors such as statistics or other marketing features.

[edit] Personal file storage
Personal file storage services are aimed at private individuals, offering a sort of “network storage” for personal backup, file access, or file distribution. Users can upload their files and share them publicly or keep them password-protected.

Prior to the advent of personal file storage services, off-site backup services were not typically affordable for individual and small office computer users.

Sometimes people prefer hosting their files on a publicly accessible HTTP server. In this case, they generally choose paid hosting, and use their hosting for this purpose. Many free hosting providers do not allow the storage of files for non-website-related use.

[edit] Content caching
Content providers who potentially encounter bandwidth congestion issues may use services specialized in distributing cached or static content. It is the case for companies with a major Internet presence

Most online file storage services offer space on a per-gigabyte basis, and sometimes include a bandwidth cost component as well. Usually these will be charged monthly or yearly. Some companies do offer the service for free, relying on advertising revenue. Some hosting services do not place any limit on how much space your account can consume. Some services require a software download which makes files only available on computers which have that software installed, others allow users to retrieve files through any web browser. With the increased inbox space offered by webmail services, many users have started using their webmail service as an online drive. Some sites offer free unlimited file storage but have a limit on the file size.

Increasingly, organizations are recognizing the benefits of co-locating their mission-critical equipment within a data centre. Colocation is becoming increasingly popular because of the time and cost savings a company can realize as a result of using shared data centre infrastructure. Significant benefits of scale (large power and mechanical systems) result in large colocation facilities, typically 5,000-10,000 m² (50,000 to 100,000 square feet). With IT and communications facilities in safe, secure hands, telecommunications, Internet, ASP and content providers, as well as enterprises, enjoy less latency and the freedom to focus on their core business.

Additionally, customers reduce their traffic back-haul costs and free up their internal networks for other uses. Moreover, by outsourcing network traffic to a colocation service provider with greater bandwidth capacity, web site access speeds should improve considerably.

Major types of colocation customers are:

Web commerce companies, who use the facilities for a safe environment and cost-effective, redundant connections to the Internet
Major enterprises, who use the facility for disaster avoidance, offsite data backup and business continuity
Telecommunication companies, who use the facilities to interexchange traffic with other telecommunications companies and access to potential clients
Most network access point facilities provide colocation.

Types of Memories. October 3, 2009

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.

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.

Computer memory refers to either of two types of computer storage. Volatile memory refers to RAM that needs to be constantly refreshed to be retained. Static memory is permanent storage that is retained even after the computer is turned off.

RAM or Random Access Memory is volatile memory that is erased when the power goes off. Program instructions and data held in RAM can be accessed and saved much more quickly than that held in permanent storage. Therefore, files needed to run a program and data that is being processed are held in RAM while they are in use. The amount of RAM you need depends at least partly on the operating system( a program that directs all the basic functions of a computer such as accepting commands from a keyboard, displaying input on a monitor screen, and controlling disk drives and some other peripheral devices) you select as well as the type of programs you intend to run.

When you boot up the computer, in other words turn it on, the operating system or part of it is loaded into the RAM along with a variety of utilities required for normal operation. Therefore, programs and data are loaded into what’s left. As little as 2MB(megabytes) total will suffice for most DOS( disk operating system-a proprietary program that controls all the basic functions of a computer) programs. In a Windows 3.x environment, 4MB is the recommended minimum, but 8MB runs far better.

Beyond operating system demands, the amount of RAM required depends on the applications to be run. For example, heavy graphics, real time video, and such need more RAM to keep things from slowing to a crawl or stop. Generally, off-the-rack machines come with 8 to 16MB, more than enough for a general purpose computer.

With improved handling of memory, reduced access times, and lower cost have conspired to make larger amounts of RAM practical. Which in turn has given programmers free rein to add more bells and whistles. This also helps programmers to become more creative in writing programs that require more RAM. There is reason to believe that this trend will continue.

As for static memory, you don’t have to be very old to remember buying a computer without a hard drive, then later installing a 20MB hard drive, unable to imagine ever needing more storage than that. Today, a 250MB hard drive is popular; however, most new computers are in the 500 to 1000MB( 1 gigabyte) range. And you may need all of that MB and then some.

Computer Memory fact #1: For the faint of heart, when programs or data files are called up from permanent storage, they are not moved, they are merely copied. If the power goes off during processing, programs generally are safe. The only loss will be data that was changed since the last save.

Computer Memory fact #2: If you decided to get a MAC computer, don’t worry. The MAC computer comes loaded with a proprietary operating system and the proper amount of RAM to run it.

Volatile memory
Volatile memory is computer memory that requires power to maintain the stored information. Current semiconductor volatile memory technology is usually either static RAM (see SRAM) or dynamic RAM (see DRAM). Static RAM exhibits data remanence, but is still volatile, since all data is lost when memory is not powered. Whereas, dynamic RAM allows data to be leaked and disappear automatically without a refreshing. Upcoming volatile memory technologies that hope to replace or compete with SRAM and DRAM include Z-RAM, TTRAM and A-RAM.

Non-volatile memory
Non-volatile memory is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory (see ROM), flash memory, most types of magnetic computer storage devices (e.g. hard disks, floppy discs and magnetic tape), optical discs, and early computer storage methods such as paper tape and punch cards.Upcoming non-volatile memory technologies include FeRAM, CBRAM, PRAM, SONOS, RRAM, Racetrack memory, NRAM and Millipede.

How to install computer memory for a computer desktop. October 3, 2009

Types of Memories October 3, 2009

Mr.Computer October 3, 2009

Computers October 3, 2009