06-17-2002, 06:30 PM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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The Flash memory interview
Crucial Technology recently contacted me about their new foray into the Flash memory business. Long known as one of the best suppliers for top-quality RAM products (they're the industry standard for RAM), it makes sense for them to get into a new type of memory: Flash RAM. CompactFlash, Secure Digital (SD), MultiMediaCard (MMC), Memory Stick, SmartMedia - they're all forms of Flash RAM. Flash RAM can be defined most simply as a storage medium that doesn't require power to maintain its state, making it a distant cousin to hard drives.
I'll be posting my thoughts on the Crucial Flash cards later this week, but I had a chance to exchange a few email messages with Andy Heidelberg, an Engineer who lives and breathes Flash RAM. Who better to answer my questions?
THOUGHTS: Thanks for answering some questions for me today Andy. What's your title and role at Crucial Technology?
ANDY: My official title is Quality Assurance Engineer. I'm part of a team that provides behind-the-scenes technical support for Crucial. In other words, I work with our Test Labs, designers, integrators, and customers on existing and future memory products.
THOUGHTS: How does the read & write speed of CompactFlash compare with normal RAM, say older-style PC-100 SDRAMs (likely close to what we have in our Pocket PC)?
ANDY: The theoretical speeds of CompactFlash cards are slower than those of memory modules. For example, an older PC100 SDRAM DIMM has a theoretical bandwidth of 1 GB/sec and a newer PC2100 DDR DIMM has a theoretical bandwidth of 2.1GB/second. In comparison, CompactFlash cards start at about 600 KB/second. CompactFlash card speed is rated similar to the way CD Drives are rated: 4X, 8X, etc. A 4X Card has a theoretical bandwidth of 600KB/second; an 8X Card is 1200KB/second, etc.
Keep in mind, a CompactFlash card isn't really a substitute for main memory. It's more of a replacement for a hard drive. Unlike RAM, flash memory retains information even when the power is turned off, just as your hard drive does. Anyone that has worked with hard drives long enough knows how noisy they can be and has also probably seen them fail. A CompactFlash card is not only much more reliable than a hard drive, you won't ever hear it. It runs quietly.
THOUGHTS: "Quietly" is quite an understatement. I've never heard even the slightest sound from a CompactFlash card - what a great technology! Is there a danger of "over-using" CompactFlash or MMC memory? How many write cycles are they certified for?
ANDY: I suppose in theory you could "over-use" a flash card, but it's probably unlikely in the real world. For example, Crucial Compact Flash cards are rated for more than 10,000 insertion/removals and more than 300,000 read/write cycles. Our cards also have MTBF (Mean Time Between Failures) of over 500,000 hours. Those ratings mean if you use your card nonstop, it will be more than 50 years before it fails.
THOUGHTS: 50 years? By then I imagine our current methods of data storage will look positively barbaric to future generations. What can people do to minimize problems with their cards?
ANDY: When using your card, there are a couple of important things to remember to keep it operating smoothly. Most importantly, never ever pull out your card while your device is reading/writing to it. If you do, there is a very good chance you'll ruin your card and all the data on it. Also, be careful when formatting your card. Your best bet is to format the card in the device in which you'll use it. If you format the card in a PC, your electronic device may not recognize the card. Also remember to make a backup copy of your files before you reformat a card.
For storage, there are two basic things you should do. First, when the card is not in the device, try to keep it in the plastic housing (jewel case) that it came with. The cards are pretty rugged, but the jewel case helps protect it from the dog, spilled drinks, etc. Crucial ships all flash cards in a jewel case for this reason. The other basic thing you can do to help maintain the life of your flash card is to keep the batteries in your device (Pocket PC, MP3 Player, Camera, etc.) fully charged.
THOUGHTS: Good advice! Someone recently posted a photograph of their 128 meg CompactFlash card after their dog had chewed on it. Not a pretty sight! Speaking of ugly things, the price of CompactFlash cards varies widely - Crucial.com sells their 512 meg CompactFlash card for $299, while Aaronix Express sells a Type 1 512 meg card for $215, and NewEgg.com sells the 512 meg Mr. Flash brand for $189. How can consumers tell the difference, or is there one? Are all the cards basically the same from brand to brand, or are there differences in performance and power consumption?
ANDY: As with other memory products, the price of CompactFlash varies depending on several different factors, including supply and demand, quality, and the level of support, service, and warranties that come with the product. There are only a few companies in the world that make flash controllers and flash chips, so for the most part, many of the brands are very similar. One difference you will see in the cards is speed. Another is the support provided by the company that sells it.
At Crucial, we always try offer the best prices we can while making sure we stay competitive with products of comparable quality. We won't always be the cheapest, but we do believe our product gives you the best value. With Crucial memory, you not only get a high-quality product that's guaranteed to work with your system or your money back (we're active members of the CFA, and MMCA so we know that our cards are compatible), you also get convenient online ordering with a 10% Web discount and free technical support over the phone or via online chat. Plus, all our digital media comes with a five-year warranty. And in the rare case that there is a problem, returns at Crucial are easy. Plus, we currently offer free shipping in the US on all our memory products.
THOUGHTS: You mention below that speed is a factor with CF from vendor to vendor. Can you be more specific?
ANDY: As I mentioned earlier, CompactFlash speed is rated similar to the way CD drives are rated: 4X, 8X, etc. A 4X card has a theoretical bandwidth of 600KB/second, a 8X card is 1200KB/second, etc. A 4X card is pretty much the lowest speed card available today. For most consumers, that's all they really need. But here's an example of where you will notice a difference in card speeds. In just the last few years, digital cameras have gone from having VGA (640 x 480) resolution, to 1.5 megapixels (1280 x 1024), to a 2 to 4 megapixel range today. It's even higher for professional market cameras.
High-resolution cameras generate larger picture files. The larger the file, the longer it takes for the camera to capture the image and the longer it takes to transfer it to the flash card. While you can use compression to speed up the process, too much compression affects the quality of your pictures. So it's not an ideal solution.
Here's an oversimplified description of how a digital camera works. When taking a picture, the CCD (Charge Coupled Device) of the camera senses the image and then stores the data. The image file is then processed and compressed, and then stored on the flash card. Once the picture has been written to the flash card, you can take your next picture. Like your computer, the speed at which all this happens is limited by the slowest part of your system. The main components in determining how fast you can take a picture are the CCD of the camera, the imaging processing, and compression, and how long it takes to write the data to the flash card.
For a consumer market camera, most of the time between pictures (time between clicking the first picture and when the camera is ready to take the next one) is spent processing the image. So having a high speed CompactFlash card isn't necessarily going to reduce this time. However, as you go into the higher range professional cameras, less time is spent processing the image and more time is spent writing the image to the CompactFlash card. In these cases a faster CompactFlash card will allow you take more pictures (even though they're higher resolution larger files) in a shorter amount of time.
Going forward, the resolution of cameras is only going to continue to increase. As next generation digital cameras using CMOS image sensors (basically a camera on a chip) instead of CCD technology become mainstream, the need for faster CompactFlash cards will be even more important.
THOUGHTS: Certain companies like Sandisk offer "ultra high speed" versions of their cards - in your experience, are these cards worth the extra money, especially for Pocket PC use? How are they better than standard cards?
ANDY: For most applications, the speed of the card doesn't really matter. If you're a photographer who takes close-up, high-resolution pictures, then a higher speed card may be the one for you. However, if you're using a low- to mid-range camera, it really won't matter. You'll be limited by the pixel size and processing capability of the camera, not by your CompactFlash card.
CompactFlash speed is rated similar to the way CD drives are rated: 4X, 8X, etc. A 4X card has a theoretical bandwidth of 600KB/second, a 8X card is 1200KB/second, etc. A 4X card is pretty much the lowest speed card available today. This is what you get with some of the least expensive CompactFlash cards available. For most consumers, this is all they really need. Also remember that even if you're transferring data from your flash card using some of the faster methods, like USB 2.0 or Firewire, the speed rating is a theoretical speed. Going to an "ultra high speed" card may increase the theoretical amount of data that can be moved, but may not have as dramatic an affect as you might think.
While some of Crucial's lower density CompactFlash cards are 4X cards, at higher densities, everything Crucial sells is 8X, which is likely faster than some of our competition, and will be more than fast enough for the average user.
THOUGHTS: Crucial now offers MMC in capacities of up to 64 megabytes. With SD cards now shipping at 512 megabytes, MMC seems to be the poor cousin in terms of capacity and performance. Is there a niche for MMC?
ANDY: Absolutely, of the two flash types, MMC is the more cost-effective solution. OEMs (and consumers) remain very interested in MMC cards because they cost less (no royalties, simpler package) than SD. Plus, most SD slots also accept MMC cards. In effect, making MMC the more versatile (you can use it in more devices) and economical solution.
Historically, memory technologies based on open standards have been more successful than royalty based ones. MMC is an open standard without royalties; SD is not. And on the supply side, MMC is based on components from many different people. Currently, all SD cards (regardless of brand) are based on components that come from just one supplier. Along with SD cards, and most other types of flash, MMC memory density is increasing. 128MB cards are increasing in volume and there will most likely be larger cards available by the end of the year.
THOUGHTS: Interesting - I had no idea that SD was a "closed” standard supplied by one company. Looking to CompactFlash, I've seen 512 meg capacity cards in both Type 1 and Type 2. Your current offering is Type 2 - why chose that over Type 1? Is going with Type 2 a cost saving factor?
ANDY: Actually, we recently completed final qualifications on our 512MB Type I CompactFlash and have transitioned from offering Type II to Type I on our Web site. It's the natural evolution of this part.
As CompactFlash cards move towards higher densities, you'll often see Type II cards appear before Type I. Inside the CompactFlash card is a PCB that contains the flash memory and controller. With a Type I card, the chips are all on one side of the PCB. With a Type II, there are chips on both sides, which is why it's thicker. So you can make a 512MB Type II card with lower density chips than a Type I card. It's similar to what goes on in the DRAM world. Originally, we made double-sided 256MB DIMMs using 16 128Mb components. Later, when 256Mb components arrived, we started making the same 256MB DIMM single sided using 8 256Mb components.
THOUGHTS: Thanks so much for your time Andy, I appreciate it!
ANDY: No problem! I appreciate the opportunity to clarify some issues around Flash memory. Check out our web site for information on our flash memory products.
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06-17-2002, 07:11 PM
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Intellectual
Join Date: Feb 2004
Posts: 185
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My dog....
LOL 
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THOUGHTS: 50 years? By then I imagine our current methods of data storage will look positively barbaric to future generations. What can people do to minimize problems with their cards?
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For storage, there are two basic things you should do. First, when the card is not in the device, try to keep it in the plastic housing (jewel case) that it came with. The cards are pretty rugged, but the jewel case helps protect it from the dog, spilled drinks, etc. ...
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THOUGHTS: Good advice � someone recently posted a photograph of their 128 meg CompactFlash card after their dog had chewed on it. Not a pretty sight!...
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You know what Jason, Charlie (my dog) ate the jewel two days after I got one last time... Anyone have Lemon-taste CF jewel case???
I'm on my way to remove any tables that are lower than 24" in my house! LOL 8)
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06-17-2002, 07:19 PM
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Pupil
Join Date: May 2002
Posts: 34
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A comment and a question:
Most, if not all high end digital cameras store photos in a DRAM buffer before they copy them to Compact Flash. Take into account that I high end camera is able to shot between 6 to 10 full res pictures in a second, which means about 40MB per second.
SD memory cards have a transactional buffer to avoid losing memory data when cartridge is removed. �Is this technoloy proprietary or might it be integrated on other media, say Compact Flash ?
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06-18-2002, 12:00 AM
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Pupil
Join Date: Jun 2002
Posts: 46
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I am surprised, that you didn't ask about the failure of SD memory in the 38xx. It sounds from his position he may have some very useful insights on this subject. This has/is occurring with more than one brand, and over a longer period than could be accounted for by one batch being bad! He is saying that it should take 50 years to fail, but we are seeing SD memory fail in months not years!
I would love to hear his thoughts on this subject. Also the very poor performance of SD memory in the Compaq 38xx.
Grey
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06-18-2002, 12:35 AM
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Executive Editor
Join Date: Aug 2006
Posts: 29,160
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Originally Posted by Grey
I am surprised, that you didn't ask about the failure of SD memory in the 38xx.
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That's a Compaq-specific problem, not a Flash memory problem. :cry:
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07-02-2002, 04:17 PM
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Neophyte
Join Date: Jul 2002
Posts: 5
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Our cards also have MTBF (Mean Time Between Failures) of over 500,000 hours. Those ratings mean if you use your card nonstop, it will be more than 50 years before it fails
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No, that is not what it means. And it doesn't give much confidence that a Quality guy thinks that it means that.
500,000 hours means that 500,000 cards fail once per hour. It says nothing about how long an individual card will last. Quoted MTBF numbers are the reciprocal of the height of the bottom of the "bathtub" curve (i.e. the reciprocal of the failure rate of a large population of cards).
The discussion talks about how Flash cards are more reliable than hard drives. Typical 3.5" hard drives today have 1M hours MTBF. But I doubt the bearings in an individual drive will last 1M hours.
Flash technology has a wearout phenomenon, too. A flash memory cell is only good for about 1M erase/write cycles. So if you wrote it once a second, it would wearout in about 11 years. Good enough for most of us, even with strenous use such as professional digital photography.
--
Charlie
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