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Bridging The Flash Format Gap With Multi-Format Readers/ Writers

Does Performance Of These Devices Really Matter?

The performance of multi-format flash card reader/ writers is perhaps the one area where you can see some difference beyond just the form factor of these devices. As the sizes of flash cards and file sizes increase, extracting the picture/ files from the flash card can take a considerable amount of time.

The majority of the units that we tested use the USB 1.1 Interface, which has a performance cap of 12Mbps, USB 2.0 units, and offers a performance of 480Mbps, while 1394 FireWire offers a performance level of 400Mbps. Of course, the average consumer will not realize these kinds of transfer rates from flash memory products.

A variety of factors contribute to the transfer performance of flash memory products. Currently, the CompactFlash Card Format allows the most room for optimization in both flash memory and interface design performance. This was perhaps a by-product of the design of the specification, which is firmly rooted in the ATA world. For this reason, CompactFlash is used in most performance testing.

Lexar Media is probably currently best known in the flash memory arena for discussing the performance of its flash media. Lexar believes that higher performance flash modules are the key to speeding up both the read and the write times of flash memory which can be of great help to professionals who use products that can take advantage of this technology. And, in the case of a digital camera, this can provide the photographer the ability to take additional pictures more quickly or a series of pictures.

The chart below provides a look at the theoretical default transfer rate (defined as 'Sequential Write Speed') performance in kB per second or MB per second, depending on the format.

CompactFlash 4X600 kB/s
CompactFlash 8X1.2 MB/s
CompactFlash 12X1.8 MB/s
CompactFlash 24X3.6 MB/s
Smart Media600 kB/s
MultiMedia Card300 kB/s
Secure Digital Media1.5 MB/s
Memory Stick800 kB/s
xD Picture Card600 kB/s

The "X" rating was first used in the marketing and branding of CompactFlash cards by Lexar Media. Lexar defines each "X" as 150 kB per second. Other manufacturers have been slow to adopt this as a standard for rating the speed of their flash memory. Most agree that Lexar has done an excellent job in marketing the "X" factor. Although most companies claim that their CompactFlash modules are "high speed," in most cases they do not define what that speed is. In a second article in this series, to be released within a few weeks, we will test a variety of CompactFlash modules to provide a better idea of what the real performance difference is among brands.

We wanted to get another view on the Lexar "X" rating, so we asked Mike Kuppinger, Kingston's Digital Media Product Marketing Manager, to give us his thoughts on this subject.

As Kingston sees it, Lexar has created the X factor as their standard. This is not a standard adopted by the CompactFlash Association, but as you can see they have done a good job of positioning the X Factor as a speed indicator (CD Read/Write X = 150 kB per second). This being said, the "actual" performance of the CompactFlash card has more to do with the function of the host controller in the device the Flash goes into, rather than the controller in the Flash card itself. For the most part, consumers using standard digital cameras and other devices will not realize/see the performance difference between a 12X and 20X Flash card. Those consumers who want a slight performance increase due to the nature of a project are in fact paying a 30-40% premium for a minimally faster card. Based on our research we categorize this customer at 5-10% of the flash market.

What we can see from the chart above is that the 24X CompactFlash offers the highest level of performance, with 3.6 MB per second of throughput. The other formats are capped in such a way that speeding up the flash memory on these cards does not help gain additional performance. In order to realize the best performance from these Multi-Format Card Readers/ Writers, we tested them using CompactFlash media from two sources.

Many things can influence the performance of the CompactFlash media, such as the camera and the flash interface in the camera. The camera's processor speed, hardware architecture, and flash card speed all contribute to the media's overall performance. Of course, in the case of Multi-Format Readers, they can often times be far ahead of the performance of the typical camera (or other device) when reading data from the flash card or writing data to the flash card. As you can guess, many manufacturers don't invest a lot of money in the flash interface; however, in the case of a camera, they may instead invest the money in the optics to try to achieve a cost effective price point. In the case of higher-end cameras (and other such high-end devices), these devices are often able to take better advantage of the additional performance offered by higher speed flash memory, but this is not always the case. Even high end "prosumer" cameras may not be able to take advantage of higher speed CompactFlash modules and in many cases only "Professional" cameras will gain any advantage by using the fastest modules possible. However, you can see a performance difference when using these high speed modules with a USB 2.0 or 1394 Firewire reader/ writer because of the increased bandwidth offered by these two interfaces.

To get the best performance from your flash memory, particularly when using large modules (128 MB or greater) with a lot of data on them, using a faster module inserted into a card reader/ writer (with a fast interface such as USB 2.0 or 1394 FireWire) will yield the best performance. However, if you want to purchase a faster module to increase the performance of your camera, you may be disappointed due to the limitations of your camera (or other device). If your camera (or other device) or flash card reader can't take advantage of the additional speed offered by the module, it will be a waste of your money to buy a higher speed module.

CompactFlash does offer the best performance of any of the flash media on the market today, but the numbers of devices that accept this format continue to dwindle. (Try to find a current MP3 player, for example, that uses CompactFlash!) CompactFlash is mainly found on higher-end cameras. Almost all of the professional series digital cameras use the CompactFlash format. Both Lexar and SanDisk offer high-end CompactFlash modules targeted for professional and consumer applications.