IBM, AMD Speed Chips, Strain Wafers  SAN FRANCISCO (Reuters) - Researchers at IBM &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=IBM.N target=/stocks/quickinfo/fullquote"&gt;IBM.N&lt;/A&gt; and  Advanced Micro Devices Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AMD.N target=/stocks/quickinfo/fullquote"&gt;AMD.N&lt;/A&gt; have improved a chip-making  technology called strained silicon, boosting  semiconductor  performance at a time when such gains are increasingly hard to  come by, the companies said on Sunday.