Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of memory-chip designer Rambus (Nasdaq: RMBS) jumped today by as much as 13% on an analyst upgrade along with some bullish comments.

So what: JPMorgan's Paul Coster bumped shares to "overweight," which is a little odd considering that he said shares are currently fairly valued. Further boggling this Fool are his comments that Rambus should be worth between $4.25 and $4.50, considering its existing contracts and cash balance. Coster also said that Rambus should see its results improve by tapping into the mobile-device and LED-lighting markets.

Now what: Shares closed yesterday at $4.47 and finished today at $4.85, which makes it seem as if a "neutral" stance would have been more appropriate. Even using Coster's high-end $4.50 target now represents a 7% downside. Just yesterday, it tanked on a different analyst's downgrade.

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