Memory Card Shoot-Out: Four 512 MB Secure Digital Cards Compared

[Jason Dunn]

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.<br /><br />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.<!><br /><br /><span><b>The Flash Cards Tested</b></span><br />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 (<a href="http://www.handybackup.com">I know, I know</a>…). 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:<br /><br />Sandisk 512 MB SD Ultra II<br />Simpletech 512 MB SD<br />Delkin eFilm 512 MB SD<br />Delkin eFilm Pro 512 MB SD<br /><br /><span><b>Testing Methodology</b></span><br />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). <br /><br /><img src="http://www.digitalmediathoughts.com/images/simpletech512mbsd-1mbread.gif" /> <br /><i>Figure 1: HD_Speed in action</i><br /><br />The software used to measure the speed was <a href="http://www.steelbytes.com/">HD_Speed</a>. 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.<br /> <PAGEBREAK> <br /><span><b>Results: Read 256 KB</b></span><br /><br /> <img src="http://www.digitalmediathoughts.com/images/read256kb.gif" /> <br /><i>Figure 2: 256 KB data read test.</i><br /><br />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.<br /><br /><b>WINNER: Simpletech</b><br /><br /><span><b>Results: Read 1000 KB (1 MB)</b></span><br /> <br /> <img src="http://www.digitalmediathoughts.com/images/read1mb.gif" /> <br /><i>Figure 3: 1000 KB/s (1 MB) data read test.</i><br /><br />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.<br /><br /><b>WINNER: Delkin eFilm Pro</b><br /><br /><span><b>Results: Read 16000 KB (16 MB)</b></span><br /> <br /><img src="http://www.digitalmediathoughts.com/images/read16mb.gif" /><br /><i>Figure 4: 16000 KB data read test.</i><br /><br />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.<br /><br /><b>WINNER: Four way tie under suspicious circumstances</b><br /> <PAGEBREAK> <br /><span><b>Results: Write 256 KB</b></span><br /> <br /> <img src="http://www.digitalmediathoughts.com/images/write256kb.gif" /> <br /><i>Figure 5: 256 KB/s data write test.</i><br /><br />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.<br /><br /><b>WINNER: Sandisk Ultra II</b><br /><br /><span><b>Results: Write 1000 KB (1 MB)</b></span><br /> <br /> <img src="http://www.digitalmediathoughts.com/images/write1mb.gif" /> <br /><i>Figure 6: 1000 KB/s (1 MB) data read test.</i><br /><br />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.<br /><br /><b>WINNER: Sandisk Ultra II</b><br /><br /><span><b>Results: Read 16000 KB (16 MB)</b></span><br /> <br /> <img src="http://www.digitalmediathoughts.com/images/write16mb.gif" /> <br /><i>Figure 7: 16000 KB/s (16 MB) data read test.</i><br /><br />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.<br /><br /><b>WINNER: Sandisk Ultra II</b><br /> <PAGEBREAK> <br /><span><b>Overall Speed Results</b></span><br /> <br /> <img src="http://www.digitalmediathoughts.com/images/overallspeed.gif" /> <br /><i>Figure 8: Test results summary for all 512 MB SD cards.</i><br /><br />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.<br /><br /><span><b>Best Bang for your Buck?</b></span><br />Once you factor in price, however, things get a little more complex. The Simpletech 512 MB SD card <a href="http://pocketpcthoughts.pricegrabber.com/search_getprod.php?masterid=611920&prsrt=1">sells for as low as $98 USD</a> in a Pricegrabber search. The Sandisk Ultra II <a href="http://pocketpcthoughts.pricegrabber.com/search_getprod.php?masterid=2432530&prsrt=1">sells for as low as $158 USD</a>. The two Delkin cards list for as low as <a href="http://pocketpcthoughts.pricegrabber.com/search_getprod.php/masterid=689188">$97</a> and <a href="http://shopper.cnet.com/Delkin_eFilm_Pro___flash_memory_card___512_MB___SD_Memory_Card/4014-3233_9-30893644.html?tag=ob_50&orderby=50&sort=asc">$222</a> (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:<br /><br />$3.51 per MB/s – Simpletech 512 MB SD<br />$3.99 per MB/s – Delkin eFilm 512 MB SD<br />$4.26 per MB/s – Sandisk Ultra II 512 MB SD<br />$6.41 per MB/s – Delkin eFilm Pro 512 MB SD<br /><br />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.<br /><br /><span><b>Final Thoughts...</b></span><br />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.

[jonathanchoo]

I am glad I got a Sandisk Ultra II 512Mb. You want speed - its either Panasonic or Ultra II.

[CrashX]

Hi Jason,

Thanks for the review!

I'm curious about the reading of the 16Mb blocks of data. Instead of it being a possible limitation of your reader or your laptop, could it be that the software you used for testing is unable to record anything higher than the 6552 Kb/s that you noted? This is pure speculation on my part as I have no experience with HD_Speed (http://www.steelbytes.com/).

Again, thanks for sharing! :)

[bbarker]

Great article, Jason.

[whydidnt]

It seems to me from a PocketPC perspective, the read time is more important than the write, since we are primarily storing programs, e-books, MP3, etc, and want fast access to them. In this case the SimpleTech card more than holds it's own, especially from a price perspective.

If you are looking for a fast card that you can use with both your PPC and your digital camera, then the write speeds of the Sandisk Ultra seem to make sense, since that's when the write speed will be most important.

It's always good to see comparisons like this, since it seems that SD card speeds can vary greatly from one manufacturer to the next.

[Wingnut]

I read a review somewhere that found a similar limitation on the Sandisk 6 in 1 card reader. Apparently it is not fully optimized for USB 2. Sandisk recommended switching up to their 8 in 1 reader to see the true potential throughputs. The article I read was comparing 1 GB CF cards.

[Boxster S]

After getting BURNED badly with a Kingston 512MB Secure Digital card, I went on a search for a new one. I ened up getting a Transcend 45x 512MB Secure Digital card from NewEgg.com for $99 shipped. It simply SMOKES my Kingston card and the 512MB Panasonic card that I had before it (had corruption issues). I ran the same tests as Jason on my Transcend 512MB card with my internal 6-in-1 USB 2.0 reader on my desktop machine (connected with the internal USB 2.0 headers on my motherboard).

Athlon 64 3200+
Asrock K8SX
2GB PC3200 DDR SDRAM
Windows XP SP2 Build 2162
Western Digital Raptor 74GB

http://pics.atofftopic.com/Images/NFS4/results.jpg

[Jason Dunn]

I read a review somewhere that found a similar limitation on the Sandisk 6 in 1 card reader. Apparently it is not fully optimized for USB 2. Sandisk recommended switching up to their 8 in 1 reader to see the true potential throughputs. The article I read was comparing 1 GB CF cards.

Hmm...interesting. Not fully optimized, eh? That's a bit strange. I'll contact them and see what they have to say...

[rmasinag]

Guys, if you guys are really concerned about speed in the desktop. Get a good job and buy a Firewire card reader. In my unnoficial timing copying\moving a file(forgot the size) is about 1 minute on a USB 2 drive and about 42 seconds on a firewire reader. they cost about $80 but you guys spend $600 on a PPC anyways :D

Yah, Sandisk Ultras are the way to go. Because I have a digicam :mrgreen:

[vic.frampton]

This was great, but do I spend the extra money for a faster SD card for my Ipac? Is there a simple benchmark that we can use to measure performance on our PPC. Something that moves a 1 MB file from main memory to the SD card enough times to get a measure. It would be fascinating to see everyone's results.

[BobWitt]

I'd love to know where the Lexar 32x 512 MB SD stack up to the Ultra II...

All I know is it is MUCH faster than the Kingston 512 - based upon subjective evaluation!

BobWitt

[Vidge]

I'd love to see the results on a Panasonic 512. Too bad they didn't send you one.

[Jason Dunn]

This was great, but do I spend the extra money for a faster SD card for my Ipac? Is there a simple benchmark that we can use to measure performance on our PPC. Something that moves a 1 MB file from main memory to the SD card enough times to get a measure. It would be fascinating to see everyone's results.

Since you'll be reading from the iPAQ 95% of the time, no, a "slower" card is a better investment. The cards that excel at writing speeds are more important in cameras.

[Jason Dunn]

I'd love to know where the Lexar 32x 512 MB SD stack up to the Ultra II...

I'm planning on updating this test a few months from now, so I'll give Lexar another try then. I did contact them for this review, but they never got back to me.

[Jason Dunn]

I'd love to see the results on a Panasonic 512. Too bad they didn't send you one.

Here's a funny story: they DID send me one, but it turned out to be a blank plastic dummy cart! I kid you not - I then requested a REAL card, but never got it. Sigh. :roll:

[Boxster S]

No comments on my Transcend tests? I feel so unloved after all that work I did :lol:

[Vidge]

I'd love to see the results on a Panasonic 512. Too bad they didn't send you one.

Here's a funny story: they DID send me one, but it turned out to be a blank plastic dummy cart! I kid you not - I then requested a REAL card, but never got it. Sigh. :roll:

What a shame. I only use Panasonics so I would be very interested in the results here.

[peterawest]

After getting BURNED badly with a Kingston 512MB Secure Digital card...

Maybe that's why the Kingston 512MB SD card is now selling for only $62.80 after a rebate.

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=82032

[Boxster S]

After getting BURNED badly with a Kingston 512MB Secure Digital card...

Maybe that's why the Kingston 512MB SD card is now selling for only $62.80 after a rebate.

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=82032

That's why I initially bought it (and where I bought it). No wonder it's so cheap

[Jonathon Watkins]

I'd love to know where the Lexar 32x 512 MB SD stack up to the Ultra II...

I'm planning on updating this test a few months from now

Good, good. I look forward to it. Nice work. :D

[Jason Dunn]

Good, good. I look forward to it. Nice work. :D

Now that I have the article, I think vendors will be more likely to send me the product because they can see it's real. Or maybe I won't get any products because they're afraid I'll point out that they're not very fast. :wink:

[msabol]

I think I can shed some light on your read tests, and I don't think it's due to an error in testing, but a consequence of the MMC spec itself.

The MMC interface is a standardized interface, and comes from the MMC Card Association. In this spec are two interfaces: one is for identification mode, the other is for synchronous transfer mode. The spec defines the maximum card clock rate at 400 KHz for identification mode, and 20 MHz for data transfer mode, MAXIMUM. So regardless of how fast the card can retrieve data internally, it can only exit the card at the maximum frequency specificed by the MMC spec. Since the MMC spec only defines a single data line (called DAT0), the theoretical maximum bandwidth out of the card is 20 MBit/sec.

So assuming that all of the cards tested can retrieve data from their flash arrays at an aggregate rate of faster than 20 MBits/sec, then the true performance bottleneck will set right at 20 MBit/sec, and all the cards will show the same performance.

Also, remember than these cards are based around NAND flash devices, which have a relatively slow page access time (on the order of 5-10us per 528 byte page). Even the slowest NAND flash devices can read at over 100 MBit/sec, and even accounting for firmware overhead (error correction, error detection, etc) you can see that the MMC 20 MHz clock is the real limiting factor here.

I think the only way you will see a speed difference is if you were able to increase the MMC card clock out of spec until the cards began to fail. Then you would see how much margin the manufacturers have built into their designs.

Lastly, realize that the card reader isn't going to dynamically change the MMC clock frequency depending on which card is inserted! I think this is the real reason why you will always read the same bandwidth for an MMC card read test.

Remember these aren't hard drives, where bandwidth is highly dependant on parameters like sector-seek speed and cache implementations. In the case of the hard drive, the IDE interface isn't the limiting factor in bandwidth, it's the drive. So those hard drives with faster seek speed will show higher bandwidth out of the drive (especially for small random block oriented tests). For the MMC spec, you are seeing the opposite.

If anyone is interested, I'll explain why the read tests are the same, yet the write speeds are different! :)

[Jonathon Watkins]

If anyone is interested, I'll explain why the read tests are the same, yet the write speeds are different! :)

Why yes Msabol, I'm interested.

Welcome and cheers for the enlightenment. Ready for part 2! :wink:

[Ekkie Tepsupornchai]

No comments on my Transcend tests? I feel so unloved after all that work I did :lol:
I've always equated Transcend to rocket-like performance. I remember a CF card comparison done on a digital camera site a couple of years back that had Transcend smoking nearly the entire field of Type I CF cards (around 15+ cards).

Ridata is another terrific brand for flash card performance.

I've cracked at SanDisk previously because their initial line of "Ultra" cards (a few years back) weren't very fast at all, but it looks like they're legitimately fast now.

[msabol]

I realized I made an error in my post above: after reading the article I thought it was referring to MMC cards! But clearly the SD versions were being tested.

Everything I said remains the same, however the SD spec defines a maximum 25 MBit/sec burst transfer rate, and also provides for a x4 mode oepration which brings the maximum theoretical burst transfer rate up to four times the 'regular' bandwidth. 25 Mbit/sec is about 3 MByte/sec, or in x4 mode a peak of 12 MByte/sec.

If the reader is truly USB 2.0 compliant, it should be capable of sustaining around 58 MBytes/sec in burst transfers, so USB shouldn't be the limiting factor in any test...however without knowing the details of the hardware/software environment this assumption may be incorrect!

One plausible explanation is that the reader itself may be underclocking the cards, which would cause a bandwidth ceiling show in the tests. But it's just a guess. Tests with transfers of large files stress the interconnection bottlenecks, not the file system overhead. The tests in this article may just be exposing the maximum transfer bandwidth of the reader in question. It would be useful to replicate that particular test on a different reader to see the difference in the results.

Now on to writing:

For write bandwidth, two factors are critical: first is the page programming time of the NAND flash device in the card, and the second is the block erase time of NAND flash. These dictate how fact the card can accept new data, or change existing data on the card. Obviously those cards based on fast NAND flash devices are going to sustain a higher write throughput. Cards based on SLC type NAND flash devices in general erase and program the fastest, however are generally found on the smaller, more expensive cards (the higher speed rated cards). Those based on MLC type NAND flash devices program and erase slower, are somewhat cheaper, and can have higher capacities for the same approximate price.

You also see the write performance seems to depend greatly on the same brand of card with different file transfer sizes. In general, card controller makers have the flexibility to tailor their garbage colletion algorithms to favor frequent update of smaller files, at the cost of increased file system overhead. You can see that those cards are better suited to systems utilizing SD cards as file system storage, like in PDA's. You will observe better performance due to the intended use of the cards. One some of the other cards, they are optimized for larger file use and have smaller overhead in file management, but the small file access suffers. These would be better suited to digital cameras, where the file size is roughly constant, and large (relative to the first case).

I hope this helps.

[davea0511]

I thought this was excellent, but I'm not sure most visitors will perceive these numbers correctly - especially with regards to the $ per speed numbers.

It all depends on why you are using the memory.

PDA USERS

READ SPEEDS - Not that important for most PDA users. Even if they frequently close and restart programs @ 2 Mb+/second the bottleneck getting the program up and running is never the card.

WRITE SPEEDS - Very important if frequently changing media, otherwise it is not very important for PDA users either. This should be a consideration if you frequently write new media to your cards (like MP3s, or movies). You generally want to be able to write this data ASAP to the cards via USB2 or Firewire - thats where you see the card speed making a difference.

DIGICAMS
The cards must be able to write data ASAP - this is critical for good digicam performance. So Fast writes are extremely important. Reading again is much less important since the bottle neck for "picture review" on all cameras LCDs is not the memory, Also most people have two cards so they can use one while the other is downloading to the PC, again showing that read-speeds are not nearly as critical in most cases.

COST PER READ SPEED
With these considerations its quite obvious that the write speed is much more important for most users - the read speed will have negligible impact on performance in most cases. With that in mind, it makes sense to consider just the cost per read speed, instead of combining read with write. This is the result:
http://www.s-l.us/Image1.gif

Note that Jason came to the same conclusion as me (Sandisk is the best value), but by different means, and this evaluation demonstrates just how much of a better value the Sandisk is.

[davea0511]

Let me add, according to the above evaluation, if you seldom change the media on your card, and if you will never the card in a high-speed digicam, then the Simpletech is a better deal. In fact, it's a great deal if that's your use.

[Jason Dunn]

I thought this was excellent, but I'm not sure most visitors will perceive these numbers correctly - especially with regards to the $ per speed numbers.

That's why I have this paragraph as my closing statement:

"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."

I appreciate your analysis, but I disagree with this part:

READ SPEEDS - Not that important for most PDA users. Even if they frequently close and restart programs @ 2 Mb+/second the bottleneck getting the program up and running is never the card.

On a typical Pocket PC, the SD card is going to be read quite often:

1) Starting EXE files
2) System drawing icons
3) Audio/Video files being opened
4) Saved games/saved data being opened

So I think that for the average Pocket PC user, the read speed is still fairly important, though not worth spending 2x as much on a card.

This should be a consideration if you frequently write new media to your cards (like MP3s, or movies). You generally want to be able to write this data ASAP to the cards via USB2 or Firewire - thats where you see the card speed making a difference.

An interesting point. It really depends on how often they do this, but you're right, if the user is dumping a 400 MB movie onto the card on a daily basis, getting a card that's 200% faster than another will save a lot of time!

Thanks for chiming in, I appreciate your thoughts. :-)

[ctmagnus]

Too bad you didn't get a Lexar to test; that may have been interesting. I just recieved a Lexar 256MB (warranty work) and it copied over in six minutes what took over 20 minutes to a Sandisk of the same capacity last night.

[davea0511]

I agree that there is a difference in program operation due to read speed - but lets do the math to see how significant it is:

First of all let's look at the difference between the fastest and slowest reading card at sub 1Mb speeds = (6250 Kb/s - 6050 Kb/s) = 200 Kb/s. That sounds like alot until you calculate the percent difference = 200/6050 = 3.3%. But that's worst case - you aren't even going to see nearly that big of a difference during normal program operation.

So lets calculate the actual expected speed difference during normal program operation due to the disk reading operations you mentioned. Most of the card access during program operation is for files in the 1K to 64K range, and those operations are likely not to occur more than every 10 seconds (unless the program is written very poorly since nearly all of that data should be cached in ram instead of constantly reading from the card). From the following math it appears the worst case for normal program operation will yield a 0.1% difference between the fastest and slowest readers. (64K/6050K/s = .01 seconds per 10 seconds = 0.001s/s = 0.1%).

Lastly, for streaming media a difference won't even exist because most PPC streaming media won't even play smoothly unless the bit-rate is below 256K/s. The slowest reading card is 6050K/s , 24x faster than the highest bitrate that your PDA can even reliably stream videos (6050/256 = 24).

So I have to hold to my position that read speeds should not even remotely be a consideration for PDA use. Its all in the math.

The only thing one should consider when buying a card is whether they will be frequently writing to the card, and if so then Sandisk is the hands down winner from both a performance and value perspective.

ps - if there is a program that reads from the card as high as 10 per second then get rid of it. That's 36,000 per hour, or a 100K per day if you use it for 3 hours per day. Reading is not a problem, but if it is reading program variables instead of storing them in RAM then it is probably writing them just as frequently - and most flash cards go bad after a million writes. That means in 10 days your card will be bad.

[davea0511]

Too bad you didn't get a Lexar to test; that may have been interesting. I just recieved a Lexar 256MB (warranty work) and it copied over in six minutes what took over 20 minutes to a Sandisk of the same capacity last night.

What does "copied over" mean? You were reading from or writing to the card? Also, which Sandisk card was it? Note the older flash cards were a lot slower than the newer ones. Tons slower.

[ctmagnus]

From the desktop to the card.

The Sandisk is a AR0306LR and iirc it's ~ nine months old.

[davea0511]

From the desktop to the card.

The Sandisk is a AR0306LR and iirc it's ~ nine months old.

Was this with their proprietary "jump-shot" cable? If so, then from what I've read you won't get the same performance advantage if using a normal CF card reader, or when it is in a device.

If however you are simply writing tons of data to the card on a regular basis seperately from the PPC or your camcorder, a Lexar with the Jump-shot cable sounds like the fastest combo.

[Jason Dunn]

So I have to hold to my position that read speeds should not even remotely be a consideration for PDA use. Its all in the math.

Ok, ok! If I agree with you will you stop arguing your point? :lol: (you're right though, the % difference between read rates is very small - writing is the real difference between the cards)

[Jonthepom]

Thanks for the excellent article Jason. Lots of good feedback. A couple of suggestions for the next version:

http://www.dane-elec.fr/us/
http://www.pretec.com/

I am a late commer to PPC so would like to know the difference between CF and SD - any one.

[Jonathon Watkins]

I am a late commer to PPC so would like to know the difference between CF and SD - any one.

Welcome to the party Jonthepom. 8)

CompactFlash cards are the older of the two technologies, offer larger capacities (you can buy a 6Gb CF card today, while SD cards are at 1Gb) and are generally cheaper per Mb than SD cards. They are often used by professional digital cameras and currently offer more I/O options than SD cards (GPS receivers etc.).

SD cards are a newer, smaller format that most of the tiny PPCs and cameras use. They tend to draw less power than CF cards. MMC cards are generally interchangeable with SD cards as they are the same size and use the same card slot, and are often much cheaper than SD cards, because they're an 'open' standard (SD card manufacturers have to pay royalties, and MMC card manufacturers don't.

There are of course other formats available, thought CF and SD/MMC are the most common and the best to stick to. For more info on the different formats have a look here (http://www.filesaveas.com/memorycard.html).

Personally I like a PPC that can take both formats, as my camera takes CF cards and SD cards are readable by many other kind of devices and are 'the future'.

[Len M.]

Perhaps Jason might run SPB Benchmark on all four cards with them installed in a PDA, perhaps an iPAQ h2215 or h5555, or a Toshiba e755 or e805.

Our PDAudio-CF card records high resolution 24/96 digital audio to mass storage, and therefore requires a very fast memory card. We've run many benchmarks using SPB Benchmark and found that the fastest PDA can only support roughly 1.8 MB/sec maximum read and write rates (that's roughly 12x). Most can support 1.2 MB/sec at most, and many much less.

You can see our benchmark results at:


http://www.core-sound.com/CF-and-SD-mass-storage-comparison.html



So even if an SD card can support higher data rates on a PC when installed in a fast USB 2.0 or Firewire card reader, it won't help PDA owners.


Len Moskowitz
Core Sound
www.core-sound.com