What is mmc card. An overview of MMC and SD memory cards, as well as a Pretec card reader. Getting to know the test subjects

Introduction One of the observed trends among memory cards, in addition to the self-evident increase in their performance, is their further miniaturization, in the light of which the prospects for the most popular CompactFlash media until recently seem increasingly vague. In this article, we will try to evaluate the performance of two MMC and SD memory cards from one of the largest manufacturers of Pretec Corporation. But not only they will become the object of our attention. In such delicate matter As a clarification of the real speed of memory cards, devices that read information from them always pay very significant attention to the final results. Unfortunately, we have to determine the speed of reading and writing compact media indirectly, and not directly. The "superfluous" link in the chain becomes a card reader, which has its own characteristics. It is he who, in most cases, is the reason that we are unable to achieve the performance of memory cards declared by manufacturers. For this reason, we were particularly interested in the new Pretec card reader, which we decided to compare in efficiency with the SanDisk device we used earlier. In order to get a more objective picture here, we decided to re-measure the performance of the previously tested memory card A-DATA Turbo SD, which then showed not so high results that one could count on, based on the declared characteristics.

Pretec e-Disk II USB Card Reader

Pretec MMC Plus 1 GB

Pretec SD 133x 2 GB

Test Methodology

FC-Test version 1.0;
AIDA version 3.95.

Motherboard - Albatron PX865PE Pro;
Central processor - Intel Pentium 4 2.4 GHz;
Hard disk - IBM DTLA-307015 15 GB;
Graphics adapter - Radeon 7000 32 MB;
RAM - 256 MB;
Operating system - Microsoft Windows 2000 with Service Pack 4.

FC Test

AIDA32

Linear Write Speed



Linear Read Speed



Average Access Time

Linear Write Speed



Linear Read Speed



Average Access Time

Linear Write Speed



Linear Read Speed



Average Access Time

Linear Write Speed



Linear Read Speed



Average Access Time

Linear Write Speed



Linear Read Speed



Average Access Time

Summarizing

Multimedia Card (MMC) is a portable flash memory card used in digital cameras, mobile phones, etc.

MultiMedia Cards were developed in 1997 by SanDisk and Siemens based on Toshiba NAND memory, have a seven-pin connector (designed to minimize the risk of contact damage), the card consists of a plastic shell and a printed circuit board on which the memory chip is located, microcontroller and contacts. Despite the serial nature of MMC, data and commands can be transmitted simultaneously. MultiMedia Card works with voltage 2.0V-3.6V, but there are also options with lower power requirements. The SD Card is a nine-pin interface developed jointly by Matsushita, SanDisk and Toshiba in 2000.

There is also a Micro Memory Card (MMC), which is structurally identical to the Multimedia Card, but differs in logical layout and is intended exclusively for use in SIMATIC S7 programmable logic controllers from Siemens AG.

Size 24×32×1.5 mm.

Since 2004, also available in a reduced case 24×18×1.5 mm

end of form start of form With a simple mechanical adapter, RS-MMC cards can be used with equipment designed for "full size" MMCs. Dual Voltage Reduced Size MMC (MMCmobile) are also available, which can operate not only on the standard 3 V supply voltage, but also on 1.8 V.

MMC is mostly compatible with the later developed SD card and can be used instead of SD. In the opposite direction, replacement is most often impossible, since SD cards are thicker than MMC and simply mechanically may not enter the MMC card slot.

MMC uses a relatively simple open data transfer protocol, therefore, unlike Secure Digital (SD), it can be used in homemade devices.

Various memory cards are typical representatives of external flash drives. Today, many of the devices we use, such as cell phones, cameras, media and MP3 players, and others use memory cards as storage media.
We believe that it would not be superfluous to know the features that different types of memory cards have, each of which is designed for a specific device.

What's inside these cards...

Flash memory is a type of data storage, the main purpose of which is to increase the functionality of modern mobile devices. This allows manufacturers to lead the market and produce equipment demanded by users. A huge plus of memory cards is the absence of additional power requirements, they are content with what is already available in the device where they are used. The punishment of memory is easily filled with information and just as easily released from it. There are no mechanical moving parts in it, so it requires a minimum of power and its life is practically unlimited. Memory cards allow you to rewrite information from tens of thousands of cycles to a million.

The period of data storage on these devices is quite long and ranges from 20 to 100 years. Another plus is the low sensitivity to external influences, vibrations and shocks.

But one of the most important advantages of memory cards is their compactness. With a thickness of three millimeters or less, the card has a maximum length of only four centimeters.

Variety of varieties

In the documentation for your device, there is always a description or abbreviation for the type of memory cards that this device can use. Having decided on the type of card, select the manufacturer, focusing on the most famous and already established manufacturers. Some of them have memory cards equipped with various adapters that significantly increase functionality and allow using the memory card in other devices.

To date, there are seven main types of memory cards.
compact flash, otherwise CF, consisting of two types - CF type I and CF type II. These types of memory cards are the most common because of their features, which sharply distinguish them from other types of compact storage media. Possessing high speed data exchange and providing a fairly high amount of memory, these cards have, in the aggregate, a very low price in terms of megabytes / ruble, which is very attractive both for those who produce mobile devices and for those who use them. According to all available data, this is currently the most common type of memory card.

IBM Microdrive- another type of memory card, for which it does not quite fit this definition, format Compact Flash type II due to the fact that it is practically a reduced copy of the hard drive. Having a cost much lower than other types of memory cards, but is a less reliable device due to moving parts. Another negative feature of this card is the higher power consumption. Therefore, rare manufacturers use this variety in their products, the connectors of which correspond to CF type II.

smart media- is also a representative of inexpensive and compact flash cards (only one millimeter thick). The low cost of these cards is determined primarily by the use of available components, but this, in turn, is also a disadvantage, since the use of inexpensive components can lead to abnormal cases and may cause loss of information.

Multimedia Card (MMC)- This is, perhaps, one of the best representatives of memory cards of this class, the main advantages of this type of memory cards are small size and low power consumption. True, all this affects the speed of information exchange. The dimensions of these cards are 24x32x1.4 mm, and the short one 24x18x1.4 mm. They are mainly used in cell phones and other devices that have a very compact size.

SecureDigital (SD)- With their dimensions, these memory cards are slightly inferior to MMC, but they are more preferable from the point of view of the speed of information exchange when working with large data sizes. This feature dictates higher prices for them.

microSD- practically in terms of its characteristics it is not inferior to SD, while having smaller dimensions. Almost all memory cards of this type come with adapters to SD /

SD and MMC backwards compatible, so MMC memory cards can be installed and used instead of SD, but alas, reverse actions are not possible. Moreover, in the latest versions of devices manufactured by manufacturers (phones, players), only an SD type connector is installed to introduce the universality of the card (it is even referred to in the documentation as an SD / MMC connector).

memory stick- made specifically and is used almost exclusively in devices manufactured by Sony. The dimensions of this memory card are 24 * 32 / 1.4 (2.1) mm. The card is very protected from outside interference, and in terms of its performance it is very similar to a memory card - SecureDigital (SD). However, its weak point is the small amount of stored information.

According to the latest statistics, at present the most common, generally accepted and used are memory cards of types compact flash and SD/MMC.

For ease of evaluation appearance and dimensions of various types of cards, we will show them clearly:

1 = MMC Plus (Multimedia Card)
2 = SD Mini (Secure Digital)
3 = SD Micro (Secure Digital)
4 = MMC Mobil (Multimedia Card)
5 = MS Pro (Memory Stick Pro)
6 = MS Pro Duo (Memory Stick Pro Duo)
7 = RS MMC (Multimedia Card)
8 = SM (Smart Media)
9 = CF (Compact Flash)
10 = SD (Secure Digital)

So what to choose?...

Usually given task one of the easiest, you just need to know what type of memory card can be used in the device you bought. You can easily learn this from the documentation for your device or from the inscriptions on the case. The only thing you can personally do is to choose the manufacturer based on your preferences.

What volume...?

In general, the question is trivial. You can count by the number of photos, time of music or video, but as a rule, no matter what you choose, it always becomes small.

The most important thing is to decide how much you are willing to spend on it, for most, the choice is reduced several times at once. After all, with a large amount of stored information, high speed of its exchange, minimum dimensions, the price may be too high for you to be able to afford it. So just choose the largest amount you can afford.

No sooner had we gotten used to cards that conform to the SD 1.1 specification (and most devices still only support the slower SD 1.0), a transition to SD 2.0 loomed on the horizon. It can be assumed that, as a result, 1.1 becomes a "passing" version, and you should not pay attention to it. In fact, everything is different. There is a feeling that the implementation of SD 2.0 will be even slower and more painful than the transition from 1.0 to 1.1 or even from MMC 3.0 to 4.x. Most likely, this process will resemble the transition from MMC to SD, which, by the way, did not end as a result - instead of the death of MMC, which was repeatedly predicted (including by me), this format, on the contrary, recently gained a second wind. The reason is the same - the lack of backward compatibility of SD and SDHC (this logo will be worn by all cards that meet 2.0 specifications). If an SD 1.1 card can be safely used in conjunction with devices designed for SD 1.0 (albeit at a lower speed - as much as was possible in 1.0), the same applies to MMC 4.x / 3.0, then the SDHC card will work in the "normal" SD device will not. Thus, an SD 1.1 or MMCplus card could be bought for the future, but SDHC could not. At the same time, SDHC devices will be compatible (when available) with conventional SD cards, so the latter can be safely purchased. Not the fact that you will lose something later. Why? Let's see what SD 2.0 brings us.

Just a bug fix

The transition from SD 1.0 to 1.1 doubled the maximum speed, the transition from MMC 3.0 to 4.0 gave us, in fact, new cards, but what does SD 2.0 give? Officially, there are only two things - an increase in the maximum volume of cards and Class Speed ​​​​Rating. The second one is easier, so let's start with it.

As you know, manufacturers prefer to mark memory cards according to the maximum reading speed, and according to the theoretically possible one. Not all and not always, but in most cases we observe just that. The write speed, if indicated, is also the maximum, and even then not always, and only in the specifications and in small print. And the reading speed (the notorious "X") is most often indicated directly on the card in arshin (compared to the size of the card itself) letters. However, it is far from always at least close to the write speed (a vivid example is MLC chips, where the difference is several times by definition), and it is difficult to achieve high values ​​of the latter in the case of flash. Manufacturers do not indicate it - it is unprofitable. As a result, the purchased "high-speed" card can easily turn out to be slower than the "regular" one, which we have encountered more than once. At the same time, in many areas of application, reading speed is not very important (just think - photos after a vacation will be copied to a computer in 10 minutes, not 5: no one will die), while writing speed is critical. An example is the same cameras, where a low recording speed simply will not allow continuous shooting. The situation is even worse with video recording, where flash is gradually becoming one of the most commonly used media: low write speed will make shooting simply impossible due to the fact that most frames will “drop out” with an obvious end result. The first attempt to sort out the mess with markings was made by the MMC alliance: the MMCplus card must not only support the 4.x specification, but also have a minimum steady-state write speed of at least 2 MB / s. The SD association went even further by introducing three card classes: Class 2, Class 4 and Class 6. The numbers here are not abstract values, but the established minimum write speed - 2, 4 and 6 MB / s. The innovation is useful, but not so vital: our tests show that today the vast majority of even inexpensive cards are quite capable of handling a stream of 6 MB / s. On the other hand, it will become easier when buying: for example, if you know that SDHC Class 6 is required to fully realize the capabilities of a photo or video camera, then you should look for such a card without rummaging through test results and descriptions on manufacturers' websites. Of course, the possibility of abuse by the manufacturer remains in theory, but in this case, he will receive not only lamentations from the deceived user on various forums, but also persecution from the Association, which is unlikely to be done by anyone (even from small companies).

As for volume, the situation is simple and understandable. Officially, the capacity of today's SD cards cannot exceed 2 GB. The limitation is not physical, but logical: the reason for this is the file system used - FAT16. The latter also supports volumes over 2 GB, but with a non-standard cluster size, which most household equipment manufacturers will not do. And for SDHC, the official file system is FAT32, so the restriction is almost lifted. However, some upper frames have been included in the standard so far - 32 gigabytes, however, compact cards still grow and grow up to such a capacity (and prices keep falling :)). In the end, some of the formats support large volumes, but cards of at least 16 GB, not to mention 32 or 64, are not yet visible;) Thus, from this point of view, SDHC is an obvious step forward compared to SD . However, somewhat blurred by the fact that some hardware manufacturers have already mastered FAT32 support in SD 1.1. And manufacturers of memory cards responded to this with the release of SD-cards with a capacity of 4 gigabytes. Such cards even in our area already cost less than $100. They will subsequently work in technology with SDHC support (I remind you that there is compatibility in this direction), and no one will fix devices that do not support such cards anyway, since SDHC will definitely not work in them;)

This is what makes the transition from SD 1.1 to 2.0 different from the transition from 1.0 to 1.1. In the second case, we could simply buy new cards and wait for the appearance of new devices that will allow us to reveal all their capabilities. In the first one it is necessary first wait for the market to saturate with SDHC-enabled devices, and after buy cards, as they are useless for older devices. And even then, you can still use regular high-capacity SD cards, since they will work in the future. It is possible that in the present, but this particular device needs to be checked. So far on the SanDisk website, I have found only seven SDHC-compatible devices with all the consequences. We can say that actively announced in recent times SDHC-cards with a capacity of 4 GB are simply useless - you can buy a regular one of this capacity. When you want to get an eight gigabyte card, it's another matter: there will be no alternatives to SDHC. But first you need to purchase a device in which you can use such a card.

And how can this affect the "popular" volumes up to 2 GB? No way - SDHC-cards of such capacity are not planned. This segment of the market will remain the patrimony of SD 1.1, but many users at the current price level do not even need two gigabytes. That is why testing SD 1.1 cards continues to make sense, and this situation can last at least another year, or even more. After the appearance of the specifications of version 4.1, the MMC alliance does not make any sudden movements - first you need to master what the standard already allows (fortunately latest version specifications was developed a little later than in the case of a competitor, and it was much more revolutionary than SD 1.1 - as a result, quite standard cards MMC 4.x, with a capacity of 8 GB, have already been announced, and nothing in the standard had to be redone;)). We are still mainly interested in cards compatible with SD 1.1 and MMC 4.1. We will study these again. The topic of today's article is representatives of several lines of flash cards from Kingston, which belong exactly to the two families mentioned. In addition to the manufacturer, they are related, by the way, also in capacity - all in gigabytes. For many applications, it is quite enough, and the price has already dropped to such a level that you can not deny yourself anything;)

Getting to know the test subjects

According to the chronology of creation and the alphabet, it is most logical to start with MMCplus - a direct descendant of those very old good MMC cards, with a capacity of a dozen or two megabytes, from which all branches of the family tree of both MMC and SD families began their "pedigree". But the rest, in fact, are side shoots, and MMCplus, I repeat once again, is direct, although in its content (and a little in form - the contact group is completely different) significantly different from its ancestor. However, we have seen a lot of cards of this standard, so I'll tell you that its real capacity, according to Everest, is 973 megabytes, and move on.

MMC cards were originally designed with an eye on maximum compactness, but time has shown that they are too big for some applications. A new shoot sprouted from the tree - RS-MMC cards, which looked like MMCs cut to length. Later, DV RS-MMC appeared on their basis, which differed in supporting the supply voltage not only 3.3 V, but also 1.8 V - since energy consumption is directly related to voltage, the need to reduce it in mobile devices is obvious. And after the appearance of the MMC 4.0 specifications, MMCmobile - DV RS-MMC with support for new operating modes was born. If you look from the other side, you can call these cards and RS-MMCplus, fortunately for full-size models it is also recommended (albeit optional) support for a voltage of 1.8 V. At first, all RS-modifications were noticeably inferior in capacity to the base ones (for purely technical reasons ), however, as technology advances, prices for high-density flash chips decrease, and user appetite grows ( Cell phones, where such cards are in use, have long been competing with digital players with considerable success and are getting closer to the patrimony of "digital soapboxes") the gap in the case of mass modifications has been shrinking more and more. However, I have not yet seen the announcement of MMCmobile for 8 GB, and MMCplus - no problem, but in the retail network (at least in Moscow), both cards are still limited to 2 GB. We, as I said, are testing a card with a capacity of 1 GB declared or (according to Everest) 988 MB real.

The Secure Digital standard originated from MMC a long time ago, and is not its direct descendant - the cards are similar, but, strictly speaking, they are not required to be compatible in any direction (however, thanks to consumer equipment manufacturers, we can often use both, but this is achieved by using two-standard controllers). Nominally, two versions of the specifications have changed (and they existed at different times), but, as I wrote at the beginning of the article, version 1.1 will not disappear anywhere in the near future, and it will never disappear from cards up to 2 GB. We are testing just a gigabyte card, and not a simple one, but an “extreme” one. However, according to Kingston, the speed limit is at 133x, and some manufacturers have mastered 150x, but the latter can mean anything in practice, and the promised 20 MB / s at least for read operations is now quite real. As far as they are real in our case - tests will show. Let me just say that an attempt to achieve technical perfection and create cards that are universal for all applications played a bad joke with Secure Digital: no one actually uses this secure one, and it eats up the capacity of the card. According to Everest, Kingston's 1GB SD card is only 941MB.

The use of flash cards in small-sized equipment, as I said, led to the flourishing of their smaller modifications. If the MMC alliance focused on RS-MMC / MMCmobile, then the alternative from the SD association was miniSD cards. It should be noted that Alliance's position is slightly better - in the case of MMC, the cards are physically and electrically compatible by connector. The SD association did not cut, but came up with a new form factor that is compatible with the "ancestor" only with the help of special adapters. And so the features are the same - reduced dimensions and reduced supply voltage. The capacity has been reduced for a long time, but now both SD and miniSD are equally up against the limitations of the standard, that is, 2 gigabytes (in practice, however, there is a difference - “non-standard” cards of twice the capacity in the case of SD exist, and no one makes such miniSD didn't risk it). By the way - the real capacity, which is the funniest thing, in our case, miniSD has more: 949 MB according to Everest :)

And now we will measure your boy- used to say the hero of one cult cartoon. Cards, of course, are not boys (and not girls either :)), and I am not the postman Pechkin, but without measurements in our time, too, nowhere.

Test Methodology

Testing was carried out on a computer with the following configuration:

• EpoX 8NPA SLI
• AMD Athlon 64 3200+ (512K L2)
• 1 GB PC3200 DDR SDRAM
• system hard drive Western Digital WD740GD
• Apacer MegaSteno AM230 card reader
• Windows XP Pro + SP2

To measure the parameters of the subjects, the Lavalys Everest program was used. Ultimate Edition 2006 2.80, or rather, the test of disk drives included in it.

Competitors

Since we have cards of different standards, the diagrams will show everything that we have previously tested on this card reader. At the same time, among other things, we will once again compare the capabilities of MMC 4. x and SD 1.1 with each other: nevertheless, we have not tested them so much to deny ourselves the pleasure :)

Reading tests

Nobody managed to repeat the record of the ultra-fast MMCplus card from Apacer in this case. Kingston MMCplus, judging by the results, supports only four data lines and a mandatory (from the point of view of the standard) clock frequency of 26 MHz. MMCmobile is noticeably faster (most likely, due to the utilization of the entire possible bus width), but it falls short of high-speed SD cards. On the other hand, both SD and miniSD cards reach the required speed of 133x, despite the fact that no one has declared a record speed for the latter.

The read access time for most cards has long been in the range of 0.5-1.5 ms. Our current subjects were no exception. As a funny grimace of fate, one can regard the fact that their results are arranged in alphabetical order, despite the alternation of formats in it :)

Write Tests

miniSD is noticeably behind the full-sized card, although it works quite quickly. SD showed exactly the same result as the 133x from Pretec - sometimes, it turns out, you can pay attention to the X's. In the MMCplus/MMCmobile pair, the positions have changed: judging by the speed, the second card uses MLC chips with all the consequences. And the first read and write speeds do not differ, which works in favor of the theory about the narrowness of the data bus itself - the flash microcircuits themselves would “catch” more, but they are not given.

With one exception, write access times are as expected. However, the exception deserves special mention: the write access time for SD Ultimate is lower than for the fastest hard drives, although the opposite is observed for most flash drives (as can be seen in the diagram). This result is not unique - the Pretec i-Disk Diamond flash drive also quickly “responds”. At this rate, soon all flash drives will overtake their magnetic counterparts in all performance parameters;) Still, the problem with a limited number of rewrite cycles will be solved, the price reduced and that's it - solid state drives will play a funeral march to their competitors :)

Real capacity

Above (in the description of the cards) I indicated it, but for the convenience of comparison I will repeat it in the table:

What conclusions can be drawn? First, you should not count on the declared capacity - the real one is noticeably less. Secondly, even within the framework of the products of one company of the same standard, it can differ markedly. Thirdly, what I paid attention to, the capacity of MMC cards, other things being equal, is higher than that of SD: nothing is given for free in this world. The difference between the minimum and maximum in today's testing reaches 47 MB ​​- quite recently, cards with a lower total capacity were a very mass commodity (still often smaller ones are included in a set of cameras) ;)

Prices

The table below shows the average retail prices of cards tested today in Moscow, relevant at the time you read this article:

Total

Not so long ago we saw that MMC cards can be much faster than SD cards. Today we saw not the first confirmation that they are not always faster, even in ideal conditions. In old equipment, everything will be even worse for MMC - high-speed SD can lose two times in speed, while high-speed MMC can “sink” by more than an order of magnitude.

As regards the actual Kingston cards, then all of them demonstrate very decent speed performance, even when they were not promised this (when they promised, the reality corresponds to the promises). At the same time, they are distinguished by a democratic price, which, coupled with the popularity of this brand and a good warranty period, makes them a very reasonable candidate for purchase. All. And which ones - depends on your preferences (or rather, the preferences of your digital equipment) in terms of tires and form factors.