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SDRAM vs. Flash Memory
Recently, the digital camera market is flooded with inexpensive entry-level cameras. I have became interested in getting some of these cameras to keep around the house, in the car, at my office, and other remote locations. Since then, I have seen two types of entry-level cameras: the type with SDRAM and the type with flash memory.
SDRAM stands for Synchronous Dynamic Random Access Memory. Random Access Memory (RAM) is a type of computer memory that can be accessed randomly; that is, any byte of memory can be accessed without touching the preceding bytes. RAM is the most common type of memory found in computers. Dynamic RAM (DRAM) needs to be refreshed thousands of times per second, or its content vanishes. SDRAM is a type of DRAM that can run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU bus speed, which is several times faster than DRAM. But all this computer mumble-jumbo is insignificant to us. What is important is that SDRAM and DRAM are volatile, meaning that they lose their contents when the power is turned off.
Flash memory is a special type of electrically erasable programmable read-only memory (EEPROM) that can be erased and reprogrammed in blocks instead of one byte at a time. Flash memory does not need to be refreshed. Many storage cards today uses flash technology: CompactFlash, SmartMedia, Secure Digital, xD Picture Card, Memory Stick, and so on. Most importantly, flash technology is non-volatile, meaning that it does not lose its information once power is removed.
How is this significant?
As photographers, we expect to be able to retain our pictures when we change batteries in our digital camera. If the camera hangs or get stuck, we might need to do a hard reset by removing power. And we might leave our cameras sitting in our closet, in our car, or in our office, waiting for the opportune moment. The camera may drain and run out of battery during those times. Like film cameras, we do not expect the pictures to be lost when we lose power.
Therefore, it surprises me that there are many cameras on the market built with SDRAM. SDRAM requires power to be constantly drained to refresh the storage memory. When the power is depleted, the data (pictures) are also lost. It baffles me why anyone would build a camera that uses a volatile memory like SDRAM.
I bump into such a problem just recently. After trying the Gear To Go CyberPix (see my review article), I realized that a camera built with SDRAM just does not cut it for any photographer. It is after trying such a digital camera that I have decided to write this article. I have and will avoid the agony of losing pictures at all cost. And this agony is best avoided by using digital cameras that uses non-volatile storage, such as built-in flash memory and/or using removeable flash storage cards.
Copyright © 2004 by Chieh Cheng. All Rights Reserved.