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 Silicon Motion Technology (Nasdaq: SIMO) have tanked today by as much as 19% after the semiconductor company reported earnings.

So what: Revenue jumped to $64 million, with adjusted earnings per share of $0.41. Both of those figures bested the market's forecasts of $61.2 million in revenue and a $0.33 per share profit. The quarter marked Silicon Motion's highest first-quarter revenue ever.

Now what: Today's pessimism is likely tied to warnings from CEO Wallace Kou, who said that retail demand for memory cards and end demand for smartphones that include Silicon Motion's products have been weak. Kou also expects this to continue in the second quarter, although the company hopes strength in other areas will offset the softness. Next quarter's revenue is expected to be between flat and up 10% sequentially.

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