wince5.0 FAT system

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Hi all,
I had developed CF memory card driver in wince5.0.I test CF write/read
speed through copying file to/from sdram.
the read speed:330KB/s
the write speed:900KB/s
Then I test CF write/read speed through IOControl funtions that operate
read/write functions directly and not through FAT system
the read speed:4.4MB/s
the write speed:1.8MB/s

Why is its speed different so big,especially reading speed? Why is the
efficiency of wince fat system so low?

I had test ramdisk driver read/write speed in fatsystem and IOControl
funtions way,and the speed different is too so big!



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