How do manufacturers state the speeds of cd rws

Their ideal usage field is in the creation of test disks, temporary short or mid-term backups, and in general, where an intermediate solution between online and offline storage schemes is required. Data recording and erasing was achieved by heating the magneto-optical layer's material e.

DyFeCo or less often TbFeCo or GdFeCo up to its Curie point thus erasing all previous data and then using a magnetic field to write the new data, in a manner essentially identical to Sony's MiniDisc and other magneto-optical formats.

Reading of the discs relied on the Kerr effect. This was also the first major flaw of this format: it could be read in only special drives and was physically incompatible with non magneto-optical enabled drives, in a much more radical way than the later CD-RWs.

The format was never released commercially, mostly because of its inherent incompatibility with standard CD reading units. A similar situation was also present for early CD-R media, which suffered from either physical or logical incompatibilities.

Since the CD-MO was otherwise physically identical to "normal" CDs, it still adopted their spiral-groove recording scheme, which would have rendered it hard to use as a removable medium for repeated, small scale deletions and recordings not unlike CD-RW.

There were and are however some magneto-optical drives and media with the same form factor that don't have this limitation. This early introduction along with the lack of standards for disk recording software, file systems and formats, physical incompatibility as well as the introduction of the more economical CD-R disks essentially caused the format to be abandoned before commercialization [1][2], and the whole idea of a rewritable CD medium to be almost forgotten until modern phase change CD-RWs appeared.

Rewritable media can with suitable optical drive according to some manufacturers be re-written up to times. To keep rotational speed precise any track have a slight superimposed sinusoidal excursion of 0. The reflective layer is, however, a silver-indium- antimony -tellurium AgInSbTe alloy, which has in its original state, a polycrystalline structure and reflective properties.

This causes liquefaction of the material. In this state, the alloy loses its polycrystalline structure, assumes an amorphous state and lose its reflectivity.

The lost reflectivity serves the same function as bumps on a manufactured CDs and the opaque spots on a CD-R which will be read as a "0". Unlike amplification and extinction of the laser light by superimposing the reflected light with the emitted as with pressed CDs. The alloy is not melted, but returns to the polycrystalline state and is thus again reflective.

Like CD-R, CD-RW have hardcoded speed specifications which limit the allowable recording speeds to certain fairly restrictive ranges, but unlike the former they also have a minimum writing speed under which the disks cannot be reliably recorded, something dictated by the phase change material's heating and cooling time constants, and the required laser energy levels.

Since the CD-RW discs need to be blanked either entirely or "on the fly" before recording actual data, writing too slowly or with too low energy on a high speed unblanked disc will cause the phase change layer to cool off before blanking has been achieved, preventing the actual data from being reliably written.

Similarly, using inappropriately high amounts of laser energy will cause the material to get overheated and become "insensitive" to the actual data, a situation which is typical of slower discs used in a higher powered faster spec drive. For these reasons, in general older CD-RW drives lacking appropriate firmware and hardware cannot handle newer, high speed CD-RW discs poor forward compatibility , while newer drives can generally record to older CD-RW discs, provided their firmware can set the correct speed, delay and power settings for the task.

The actual reading speed of CD-RW disks, however, is not directly correlated or bound to its speed spec, but depends first and foremost on the reading drive's capabilities, as with CD-R discs.

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November and incorporated under the "relicensing" terms of the GFDL , version 1. Chat WhatsApp. Optical disc Optical disc drive Optical disc authoring Authoring software Recording technologies Recording modes Packet writing.

Optical media types. See also. History of optical storage media High definition optical disc format war. Bennett, Hugh. Steinmetz, Ralf and Nahrstedt Klara. Basic computer components. Monitor Printer Speakers Plotter. Rainbow Books. From Wikipedia, the free encyclopedia. Chatting dengan Staf :. Select Language :. Computer Science. Prev cdrtools. Supported devices include hard disks, optical disc drives, tape drives, printers, scanners, network cards, and much more.

Advantages of SAS over parallel SCSI include thinner, longer cables; reduced interference; less expensive; support for many more connected devices at once; and faster speeds. SAS interfaces have data transfer rates of MBps and higher.

The lack of moving parts makes flash memory storage more durable and shock resistant than other types of media such as magnetic hard disks or optical discs. Solid State Drives Memory Cards A memory card is a removable flash memory device, usually no bigger than 1. Memory Cards USB Flash Drives Express Card modules can be used to add memory, storage, communications, multimedia, and security capabilities to a computer Express Card Modules Types of services offered by cloud storage providers vary.

Some provide storage for specific types of files, such as photos or e-mail messages, whereas others store any type of file. Cloud Storage Some optical disc formats are read only, meaning users cannot write save on the media.

Manufacturers usually place a silk-screened label on the top layer of these single-sided discs. You insert a single-sided disc in the drive with the label side up. Other discs are double-sided. Simply remove the disc from the drive, flip it over, and reinsert it in the drive to use the other side of the disc. Double-sided discs often have no label; instead, each side of the disc is identified with small writing around the center of the disc. A lower-powered laser light reads items from the disc by reflecting light through the bottom of the disc.

The reflected light is converted into a series of bits the computer can process. A land causes light to reflect, which is read as binary digit 1. Pits absorb the light; this absence of light is read as binary digit 0. They use an X to denote the original transfer rate of KBps. Multisession means you can write on part of the disc at one time and another part at a later time. Reliability of the disc tends to drop, however, with each successive rewrite. These drives have write speeds of 52X or more, rewrite speeds of 32X or more, and read speeds of 52X or more.

When you post and share photos online on a photo sharing community, you can choose to save your collection of online photos on an archive disc. An archive disc stores photos from an online photo center in the jpg file format, usually at a maximum resolution of pixels per photo. Widely used DVDs are capable of storing 4. The first storage technique involves making the disc denser by packing the pits closer together. The second involves using two layers of pits. For this technique to work, the lower layer of pits is semitransparent so that the laser can read through it to the upper layer.

This technique doubles the capacity of the disc. Some game consoles include a Bluray drive. Original Blu-ray Disc drives had read speeds of 4. A magnetic stripe card reader reads information stored on the stripe. Smart cards contain a processor and have input, process, output, and storage capabilities. Other Types of Storage smart card To meet their large-scale needs, enterprises use special hardware geared for heavy use, maximum availability, and maximum efficiency.

One or more servers on the network have the sole purpose of providing storage to connected users. In an enterprise, some storage systems can provide more than TB of storage capacity. Optical disc servers hold hundreds of optical discs. Total views 1, On Slideshare 0. From embeds 0. Number of embeds 2. Downloads Shares 0. Comments 0. Likes 0. You just clipped your first slide!