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Old 07-26-2004, 05:00 PM
Jason Dunn
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Default Memory Card Shoot-Out: Four 512 MB Secure Digital Cards Compared

We live in a world of marketing buzz, where the letter "x" is thrown in front of a number to show how much faster something is, but how much of it is true? In the realm of flash memory cards, most vendors offer two or more types of cards: the regular version, and a professional version that's said to be much faster than the normal version of the card. I always thought that those "high speed" memory cards were something you could only take advantage of if you had a high-end professional camera, and that the extra top-end speed was wasted when used in a PDA, phone, or consumer-level device. Imagine my surprise when performing a test on a Pocket PC and I saw different numbers when using a high speed Sandisk memory card! This prompted me to do some further investigating, so I created a simple test to see how several cards from top vendors measure up against each other.

When it comes down to which card to buy, you'll be thinking about more than just speed. Other factors to consider include price, warranty, availability, and brand � this article will not address those issues. Instead, I'm focused completely on raw speed, and how the speed of the card relates to its overall value.

The Flash Cards Tested
Wanting to eliminate as many variables as possible, I focused on testing only 512 MB Secure Digital Cards. I requested cards from over half a dozen vendors, but only Sandisk, Simpletech, and Delkin responded to my request. Each vendor was asked to send samples of their currently shipping 512 MB SD cards, both the consumer level cards and their high-end professional cards (if applicable). Sandisk sent me their Ultra II card. I had already had a 512 MB consumer-level Sandisk card in my possession for a few days, and it was fully tested, but I lost my first batch of test data when Windows XP abruptly died on my laptop and I didn't have a backup (I know, I know�). Simpletech sent me a 512 MB SD card in a ProX package, but the label indicated it was their standard consumer-grade card. Testing confirmed that it was their consumer level card. Delkin sent me both their consumer grade eFilm card and their professional grade eFilm Pro card. The cards covered in this shoot-out are:

Sandisk 512 MB SD Ultra II
Simpletech 512 MB SD
Delkin eFilm 512 MB SD
Delkin eFilm Pro 512 MB SD

Testing Methodology
First, a word about the methodology I chose: Flash cards will perform differently based on what type of device is reading and writing to the card. So while a card might be blazing fast in a high-end digital camera, it might perform slowly in a phone. Thus, it's impossible to predict exact performance values across all devices. This article is focused on several constants, the only variable being the brand and type of card. The tests were performed using a Sandisk 6 in 1 USB 2.0 memory card reader connected to the USB 2.0 port on a Fujitsu P5010D laptop. No other programs were running on the laptop, and it was disconnected from the network to ensure maximum performance. No other USB devices were connected to any other port, and the laptop was connected to AC power and the CPU was set to maximum speed (900 mhz in this case).

User submitted image
Figure 1: HD_Speed in action

The software used to measure the speed was HD_Speed. Special thanks to Louis Solomon from Steelbytes for adding a timer to HD_Speed specifically for my use. Each test was run once for five minutes in length, so any speed blips would have been averaged out over time. It was for this reason that I only ran each test once � in initial repeated tests I saw zero variance in the final average after five minutes. Six tests were performed in total: three tests to benchmark how fast a device could read data from the card, and three tests to measure how fast a device could write data to the card. Each test utilized three sizes of data blocks: 256 KB, 1 MB, and 16 MB. I felt that these represented common scenarios: reading/writing files on a PDA (256 KB), taking and viewing photos (1 MB), and reading/writing RAW files in a high-end camera (16 MB). Those values are approximations of course, because every device will have different file sizes � my Canon EOS 300D takes JPEG images around 2 MB in size and the RAW images are 10 MB or so. The test sizes I used are a "best effort" approximation.

Results: Read 256 KB

User submitted image
Figure 2: 256 KB data read test.

Surprisingly, the consumer-grade Simpletech card pulled ahead of the pack with a speed of 6194 KB/s. Besting the more expensive pro card is no mean feat, but the slowest card in the pack, the Delkin, still hit 6092 KB/s. Bottom line: with small 256 KB files, all these cards are extremely fast and there's little significant difference between them.

WINNER: Simpletech

Results: Read 1000 KB (1 MB)

User submitted image
Figure 3: 1000 KB/s (1 MB) data read test.

This is where we start to see more significant gaps � the Delkin eFilm Pro, which trailed the Sandisk Ultra II in the 256 KB test, pulls ahead here with a score of 6246 KB/s. It's interesting to note that the consumer-grade Simpletech card is matching the more expensive Sandisk Ultra II card. The Delkin eFilm card is dead last, and when reading 1 MB files the difference between these cards starts to become more obvious.

WINNER: Delkin eFilm Pro

Results: Read 16000 KB (16 MB)

User submitted image
Figure 4: 16000 KB data read test.

This test proved to be the most interesting because as you can see, all the cards ranked the same. Each card proved to be equally capable of reading big 16 MB chunks of data. Why? I'm not entirely sure � at first glance I thought with such exacting speed matches (6552 KB/s) it was a limitation of the memory card reader, but at USB 2.0 speeds of 480 mbps, it should theoretically have a hard limit of 60 MB/s. Even if we factor in 50% overhead, we're still at 30 MB/s. So why did these cards top out at 6.5 MB/s? It's likely that the Sandisk USB 2.0 card reader and the ports on my laptop top out at 6552 KB/s, which is more than a little disappointing if that's the case. 6.5 MB/s is a long way from 60 MB/s! I'd be interested in hearing opinions from readers on this test. I'm going to acquire a different brand of memory card reader and will try this test again on my desktop computer to see if any differences are discovered.

WINNER: Four way tie under suspicious circumstances

Results: Write 256 KB

User submitted image
Figure 5: 256 KB/s data write test.

Once the results started to come in for the write tests, I knew this was where the differences would really show up. As you can tell from the chart above, the differences when writing 256 KB chunks of data are drastically different from reading 256 KB chunks. The consumer grade Delkin eFilm managed to write at 1714 KB/s, while the eFilm Pro card blasted away at 5052 KB/s. The speed crown on this test goes to the Sandisk Ultra II card at 5682 KB/s, but the Simpletech card did surprisingly well at 2764 KB/s.

WINNER: Sandisk Ultra II

Results: Write 1000 KB (1 MB)

User submitted image
Figure 6: 1000 KB/s (1 MB) data read test.

The results of the 1 MB data write test were similar to the 256 KB test, but the differences were slightly more pronounced. With the larger file size, the Sandisk Ultra actually increased in performance, breaking past the 6 MB/s mark and coming in at 6040 KB/s write speed. The Delkin eFilm Pro came next, scoring exactly the same as the previous test: 5052 KB/s. Both the Simpletech and Delkin cards were a little slower than the 256 KB test, hitting 2560 KB/s and 1638 KB/s respectively.

WINNER: Sandisk Ultra II

Results: Read 16000 KB (16 MB)

User submitted image
Figure 7: 16000 KB/s (16 MB) data read test.

This last test has some surprising results: across the board, all of the cards were faster at writing 16 MB data chunks than they were at writing 1 MB data chunks. The Sandisk Ultra II delivered on its name by dishing out a punishing 6552 KB/s. That number looks familiar doesn't it? It's the same number from the 16 MB read test, which leads me to believe that the Sandisk Ultra II card is actually faster than 6552 KB/s, but my setup is limiting the measurement of exactly how fast this card can go. The Delkin eFilm Pro clocked in at 5564 KB/s, a full half-megabyte faster than it pulled off on the 1 MB write test. The Simpletech increased over 1.2 MB/s and pounded the 16 MB data files away at 3726 KB/s. The Delkin eFilm card brought up the rear at 2286 KB/s, but that's still a good 0.6 MB/s faster than the 1 MB test. Assuming that the performance of writing 2-4 megabyte files is closer to the 1 MB test than it is to the 16 MB test, it seems that most of us aren't quite using our cards to their full speed potential with smaller files.

WINNER: Sandisk Ultra II

Overall Speed Results

User submitted image
Figure 8: Test results summary for all 512 MB SD cards.

The above chart indicates the cumulative total of each card � the KB/s speed of both the reading and writing tests were added together and the results show a clear winner: the Sandisk Ultra II is the fastest card overall and the winner of this shoot out. If you want the ultimate in performance, that's the card to get.

Best Bang for your Buck?
Once you factor in price, however, things get a little more complex. The Simpletech 512 MB SD card sells for as low as $98 USD in a Pricegrabber search. The Sandisk Ultra II sells for as low as $158 USD. The two Delkin cards list for as low as $97 and $222 (eFilm and eFilm Pro respectively). Let's have some fun with the math ;-) � I've never seen anyone do this before, so this might be a first. What happens when we take the overall KB/s ratings from the six tests, convert it to megabytes per second (MB/s) and compare it to the retail cost of the card? Here's what we get from lowest cost to highest cost:

$3.51 per MB/s � Simpletech 512 MB SD
$3.99 per MB/s � Delkin eFilm 512 MB SD
$4.26 per MB/s � Sandisk Ultra II 512 MB SD
$6.41 per MB/s � Delkin eFilm Pro 512 MB SD

Surprisingly, the best combination of value and price is the Simpletech card, followed by the Delkin eFilm card. The Sandisk is the performance champ, but nearly double the cost of the Simpletech card. If performance is your #1 need, the Sandisk Ultra II is the card you want. The Delkin eFilm Pro card is a decent performer, but it's 33% more expensive and 7% slower than the Sandisk Ultra II. You won't notice a 7% difference in performance, but you will notice a 33% price difference.

Final Thoughts...
Ultimately the card you pick should be based on how you'll use it. If the SD card is going into a Pocket PC or Smartphone, and will be primarily used for reading data stored on it (audio, video, programs), the read speed is more important than the write speed. If the card is going into a camera, however, write speed is paramount and you'll want the fastest card you can get your hands on even if it's more expensive.
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