English
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GermanProductivity of the flash-memory
Evgenie Rudometov
www.rudometov.com
Productivity of cards of the flash-memory released by the numerous semiconducting companies, is defined not only the metrics declared and resulted on cards, but also hardware-software resources of used computers and maps-readers
Among various variants of the nonvolatile memory the flash-memory uses escalating popularity. Presented by miniature cards of various form factors and standards it is well entered in the architecture of modern transportable arrangements. Absence in a construction of moving mechanical units provide energoekonomichnost and high dependability of an information storage in the conditions of vibrations and shock loads. The given features promote fast implantation and growth of popularity of this type of memory.
Estimating advantages of cards of the flash-memory, it is necessary to mark, that the greatest distribution was received by models of standards Secure Digital Card (SD) and MultiMedia Card (MMC). Their size is now in a band of 16 Mb – 4 Gbytes, and mass models start already with 256 Mb. Thanks to fast reduction of prices in the market even more often is present the models concerning the upper band of size.
Informal introduction
Flash-memory cards release many known computer companies, and their number permanently increases. They differ the price, design, in size and productivity.
Usually first two parametres do not call questions. Really, the price of cards of the flash-memory is defined by the market. Their design is reduced exclusively to a variation colour raskraski tanks and to usage of bright stickers. As to size and productivity these characteristics demand more detailed explanation.
Here it is necessary to remind, that the size of memory cells is calculated in bytes and their derivatives: kilobytes (Kbytes), mbytes (Mb), gigabytes (Gbytes) and terabytes (Tbyte). Each of these units is formed by multiplication of prior unit to the coefficient 1024 representing 2 in degree 10. It means, that 1 Tbyte = 1024 Gbytes, 1 Gbyte = 1024 Mb, 1 Mb = 1024 Kbytes, 1 Kbyte = 1024 byte. Thus, for example, 1 Tbyte = 1024 * 1 Gbyte = 1024 * 1024 * 1 Mb = 1024 * 1024 * 1024 * 1 Kbyte = 1024 * 1024 * 1024 * 1024 * 1 byte. Interested persons can be convinced, that 1 Tbyte = 1 099 511 627 776 byte, and 1 Gbyte = 1 073 741 824 byte.
It is necessary to mark, that the choice 1024 is not casual. Such coefficient has appeared convenient by operation in binary arithmetics, and the computer, as is known, is the computer operating with binary numbers (0 and 1) by appropriate rules bulevskoj (binary) mathematics.
However manufacturers of memory cells calculate for a long time already size of the products not in binary, and in decimal units. It means, that 1 Tbyte is equal 1000 Gbytes, instead of 1024 Gbytes as it it would be possible to expect from the name of a unit of measure. Thus, in products of memory of 1 Tbyte = 1000 Gbytes = 1 000 000 Mb = 1 000 000 000 Kbytes = 1 000 000 000 000 byte, that is size is calculated in thousand, millions, billions and billions byte.
Translation of values of size in habitual kilobytes, mbytes, gigabytes, and terabytes with coefficient 1024 instead of 1000 leads size metrics to a little more modest results. By the way, with growth of size the difference increases: at 1 Tbyte — 10 %, 1 Gbyte — 7,4 %.
The explanation of a choice of smaller multipliers speaks very simply: in millions and billions byte size metrics look more impressive. And it means, according to experts in marketing of the companies-manufacturers, the big attractiveness of products in the opinion of potential buyers.
So, for example, value of 512 Mb », resulted on a flash-memory card means 512 000 000, and« 1 Gbyte » — 1 000 000 0000 byte.
Now about productivity. Here, as well as in case of optical disks, multiplicity coefficients use. They can be, for example, 60X, 66Х, 80X, 100X, 133X etc . As unit the speed of an exchange equal of 150 Kb\ss is selected. Thus, the card of the flash-memory flagged, say, with value 80X, should provide information interchange with a speed of 12 Mb per second (80*150 Kb\ss), and a card with coefficient 100Х — 15 Mb per second (100*150 Kb\ss).
From the resulted examples it is visible, that the more coefficient, the above productivity of a card of the flash-memory. It is necessary to mark, as here has not done without some slyness from manufacturers. The matter is that speed in write mode of the information differs from speed of reading: change of the information demands bolshego time, than simple reading. It is linked to features of operation of the flash-memory.
And how here to arrive to manufacturers, having «on hands» two values for two modes? For what mode to specify productivity coefficient? And as though you have arrived on their place, considering a hard competition in the given sector of the market? Generally speaking, the special choice in such conditions for manufacturers is not present. As a result we have on flash-memory cards bolshee value, that is what corresponds to a reading mode.
It is necessary to mark, that all it concerns also cards of standards SD, and cards of standards MMC. It is necessary to be convinced only of it, fulfilling appropriate tests. But it, generally speaking, not difficultly. And here that has turned out as a result, is resulted more low.
Testing
For testing flesh-cards from several manufacturers have been selected. Cards differ the different price, in size and productivity. Three of them — SD, and the fourth — MMC Plus (MMC +). Thus the most capacious are presented by cards SD and MMC +. They are released by one manufacturer — company Apacer, have high values of size — 2 Gbytes and productivity — 150Х and 290Х. The third model — SD is released by company Transcend, has size of 1 Gbytes and productivity coefficient 80Х. The fourth model — SD, company Kingston, without instructions of coefficient of productivity.
Appearance of the models selected for testing is presented on fig. 1, and parametres of two most capacious models — in table 1.
Fig. 1. The cards of the flash-memory selected for testing
Table 1. Key parametres Apacer MMCplus 290X 2 Gbytes and Apacer SD 150X 2 Gbytes
Characteristics |
Apacer MMCplus |
|
Compatibility with the specification, the version |
4.1 |
1.1 |
Maximum read rate, Mb per second |
43,5 |
22,5 |
Maximum speed of writing, Mb per second |
11 |
15 |
Supply voltage, In |
3,3 |
3,3 |
The sizes, mm |
24х32х1,4 |
24х32х2,1 |
Weight, g |
1,3 |
2 |
Considering orientation of cards of flash-memory SD/MMC + on sector of transportable arrangements, their operation it is expedient to estimate together with the transportable systems added corresponding maps-readers.
As the test computer notebook Fujitsu Siemens Amilo M1420 has been used. This computer incorporates: the processor — Intel of Pentium M 735 with kernel Dothan and clock rate of 1,7 GHz, a chip set — Intel 855GME + ICH4M, the built in videoadapter — ATI MOBILITY RADEON 9600 PRO c 128 Mb RAM, dynamic storage — 512 Mb DDR333, HDD — 80 Gbytes. Together with the computer used maps-readers Transcend (a Fig. 2).
Fig. 2. Maps-readers
Results of testing of cards of the flash-memory are presented in table 2 and in a Fig. 3.
Table 2. Results of testing of cards SD/MMC +
Tests |
Apacer |
|
Transcend |
|
WinBench 99/Disk Access Time (Milliseconds) |
1,11 |
1,67 |
1,64 |
10,8 |
WinBench 99/Disk Transfer Rate: Beginning (Thousand Bytes/Sec) |
1760 |
7070 |
7060 |
6870 |
WinBench 99/Disk Transfer Rate: End (Thousand Bytes/Sec) |
1760 |
7070 |
7060 |
6870 |
Fig. 3. Results of performance of test WinBench 99/Disk Transfer Rate
Results, directly to tell, have turned out unexpected. Really, any of cards with the declared metrics of productivity has not shown declared speeds of data exchange. As follows from results of testing, values have appeared essentially lower: differences in times. Also that the most interesting, card MMC + which productivity has been declared as 290Х, has appeared the outsider. It was easily overtaken by other representatives of the selected set of cards of the flash-memory. And should be with accuracy on the contrary. Also it is surprising result.
It would be possible to put an end to it, but it was difficult to believe, that the dear manufacturer could so to be mistaken. Certainly, it would be possible to write off all on a fault of the equipment or on unexpectedly failed cards of the flash-memory. But it was difficult for believing in all.
It was necessary to make changes to the test equipment and to repeat experiment.
Surprisingly, but maps-readers from the unknown manufacturer could not rehabilitate a card: results have appeared even a little bit more poorly what have been received in testing by means of the previous package.
But here changeover of maps-readers by other model, by the way, also from Transcend, has placed all on the places. Data of maps-readers it is resulted in a Fig. 4.
Fig. 4. The maps-readers, provided high speeds of operation of cards of the flash-memory
Results of testing with the computer described above and with this model of maps-readers are resulted in table 3 and in a Fig. 5.
Table 3. Results of testing of cards SD/MMC +
Tests |
Apacer |
|
Transcend |
|
WinBench 99/Disk Access Time (Milliseconds) |
0,753 |
1,12 |
1,04 |
8,6 |
WinBench 99/Disk Transfer Rate: Beginning (Thousand Bytes/Sec) |
32 700 |
19300 |
11 300 |
9640 |
WinBench 99/Disk Transfer Rate: End (Thousand Bytes/Sec) |
32 200 |
19500 |
11 400 |
9640 |
Fig. 5. Results of performance of test WinBench 99/Disk Transfer Rate
The resulted results of testing testify that flash-memory Apacer MMCplus cards 290X 2 Gbytes and Apacer SD 150X 2 Gbytes are really characterised not only the big information capacity, but a data transfer high speed. Thus high-speed parametres of the selected cards SD/MMCplus released by company Apacer, predictably, have appeared essentially above similar characteristics of two other models.
As to a difference in productivity between the real and declared values it speaks features of the used tests calculating the integrated estimation of productivity, considering both readings, and writings. Besides, declared "rate of fire" is, generally speaking, peak, and it depends both on hardware-software resources of the computer, and from model of maps-readers. Nevertheless, it is possible to notice, that places in an original rating arrange according to the declared manufacturers in coefficients of productivity.
In summary, it is necessary to mark once again, that testing has shown, what not all maps-readers "are equally useful" it Speaks that is far not all of them to the full support the standards installed for cards of the flash-memory and maps-readers. Unfortunately, very seldom, when in accompanying maps-readers documents the list of standards supported by them is resulted. By the way, as a rule, there are no similar characteristics and in the majority of other arrangements using cards of the flash-memory. Numerous notebooks, a handheld computer, audio and videoplayers concern such arrangements, kommunikatory, smart phones, phones, etc .
Considering all it, is very difficult to give guidelines how to select optimal models. Possibly, best way is a testing. As an alternative variant, it is possible to take advantage of advices of authoritative experts, friends, sellers of computer stores.
So, estimating the results received in the course of testing, it is necessary to remember, that the high-speed potential of cards of the flash-memory manages to be realised in a maximum degree only by means of usage of the appropriate means supporting necessary standards and the specifications.
Flash-memory MMCplus units 290X 2 Gbytes and SD 150X 2 Gbytes have been given by the European representation of company ApacerTechnology Inc.