Here's a good article with some very relevant examples
http://codeandlife.com/2012/04/06/level-shifting-101/

At 1MHz it's starting to becoming an issue so 10MHz will definitely be an issue. And yes the lower value resistors help but won't really fix it at high speeds. Some cheap logic will.
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Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)