SD – parametres virtual and real

Evgenie Rudometov

authors@rudometov.com

The major parametres of cards of flash-memory SD are speed and the information capacity which implementation depends on hardware support by computer arrangements of the given cards

The modern computer is extremely difficult arrangement consisting of the big number of units. However, if to lead poll, the majority of us straight off will name a small amount from them. After the central processor unit the memory providing an information storage, most likely, will be named. On an operating time of the program and processing of figures it will be dynamic storage, on long time — a hard disk. And where to carry the flash-memory?

Created as for dynamic storage the flash-memory urged to provide an alternative variant, as well as a hard disk, a non-volatile information storage. Its units differ compactness and do not contain moving parts.

Absence of mechanical parts is unconditional plus as provides raised dependability and rather low energopotreblenie. The main disadvantage of this type of memory is rather high cost of unit of an information storage. And the size long time did not allow to concern this type of memory, as to storage of programs and data, with all gravity.

Nevertheless, the last years the situation began to vary promptly. Practically annual doubling of the information at the adequate reduction of price occurring for a long time, has provided appearance of capacious carriers.

As media, perhaps, greatest distribution have received cards of the flash-memory of type SD (Secure Digital). Sizes promptly evolving towards increase and speed of operation they make a competition for disk drives on hard disks. Really, today any more a rarity of a card with size of 1 Gbytes and with the price less than $30. To estimate values of these metrics for development of the market of portable engineering, it is enough to recollect, that about five-seven years ago the same size possessed the hard disks installed in notebooks and possessing the price in five-seven times bolshej, than the specified cards of the flash-memory.

And in the bar of cards SD already mass there are models in size of 2 Gbytes, for example, such as on the Photo 1.

Photo 1. A card of flash-memory ApacerSD of 2 Gbytes

Similar against each other as brothers-twins, cards SD of different size, nevertheless, differ in high-speed parametres and brands of manufacturers.

Not pressing in discussion concerning popularity of brands, it is expedient to stop on other parametres and some consequences following from their values.

Estimating parametres SD, it is necessary to mark, that rare the cards labelled by numbers 66, 80, 133, 150Х etc. now are not . Here as for CD and DVD, the more the given parametre, the above as much as possible accessible speed of an exchange of figures. And here small opening disappear.

Let's do small experiment by experimental definition of high-speed parametres of three cards SD: Patriot SD 512 Kbytes (without instructions of high-speed coefficient), Transcend SD 80X 1 Gbyte, Apacer SD 150X 2 Gbytes.

As testing hardware used notebook Fujitsu Siemens Lifebook 7010 and Card Reader Transcend USB2.0. Considering, that modern cards SD are taken up a position as changeover of hard disk drives, software are presented by known benchmark package WinBench 99. Results of testing are presented in Table 1.

Table 1. Results of testing of cards SD

The intrigue of the given experiment consists that hardware support is necessary for implementation of high-speed parametres. The matter is that the card does not exist in itself, and works as a part of any arrangements. And they are capable to work on very high speeds?

For an estimation of justice of such question it is enough to recollect besides CD/DVD disks. High-speed carriers are capable to justify our waitings only by operation with appropriate arrangements. It is fair and with CD/DVD disks, and with flash-memory SD cards. Boundedness of possibilities of maps-readers practically equal values of transfer rates for SD 150X and SD 80X speak. Though it is necessary to recognise, that these values are high enough.

In addition to the received data the estimation of time parametres SD has been fulfilled at synchronisation from handheld computer Fujitsu Siemens LOOX 420. Between the given arrangements avi-file DivX in size of 302 Mb was handled with simultaneous code conversion .

Results of testing (less – it is better) are resulted in Table 2.

Table 2. An estimation of time parametres SD at synchronisation from a handheld computer

As the information transfer rate in real tasks quite often essentially below the declared values follows from the data presented in the second table, that substantially depends on hardware-software resources.

In summary, it is necessary to mark, what not all arrangements are capable to work with vysokoemkimi carriers. So, for example, all hardware are compatible to cards SD far not. About it many manufacturers, both cards, and readers, and also various arrangements with built in controllers SD warn. The original boundary usually transits between values of 1 Gbytes and 2 Gbytes. By the way, on a site of company Apacer releasing cards of the flash-memory of different types, there is a list of arrangements which are already tested on compatibility with cards of 2 Gbytes. Bessomnenija, this list will be continued, as the analysis of arrangements proceeds, and the bar of cards SD is already added by model in size of 4 Gbytes.

As to recommended values of speeds and sizes, how shows experience, for the majority of existing applications level 80Х (and even 66Х) is quite sufficient. However cards with great values of high-speed metrics can be useful to some modern, and also the future models of transportable arrangements. Proceeding from this circumstance, the choice and acquisition of such cards are quite expedient, if, of course, they do not possess the excessive price. Rather the second parametre it is necessary to be guided by the following estimation: the above card size, the better, but, selecting suitable value, it is necessary to remember a problem of possible inconsistence with some arrangements.

Flash-memory SD unit 150X 2 Gbytes has been given by the European representation of company ApacerTechnologyInc.