Force dd not to cache or not to read from cache

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http://unix.stackexchange.com – I'm working on an embedded system with the busybox version of dd. I'm trying to test an erase to the drive from some outside utility, however dd does not read from the disc again after the erase, but shows me the cached data. I've narrowed it down to dd as when I do an initial dd, see the data, restart my system to flush the cache, did the erase, and then ran dd again it came up with all zeros. However, if I do dd on factory settings, erase the drive, and do dd again without restarting it won't show me all zeros until a restart. I've read in the GNU manpage that dd supports the iflag opt, w (HowTos)