MadShrimps decided to explore the performance of ReadyBoost, using the USB interface available for SD cards.  In this particular set of tests first they benchmarked the system with 512MB, 1GB and 2 GB, or RAM and then adding the cards.  They also tried using the SD cards to replace RAM, keeping 512MB in the system, and then benchmarking with various USB/SD cards and storage space.
“Prices for mainstream Digital Cameras over 7 mega pixels are going down and they are becoming more affordable, and so do flash memory cards. Would these cards be Windows Vista ReadyBoost ready other than USB? We round up a few of these cards for comparison today.”

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