Intel Cancels Top-Speed Pentium 4 Chip  SAN FRANCISCO (Reuters) - Intel Corp. &lt;A HREF="http://www.reuters.co.uk/financeQuoteLookup.jhtml?ticker=INTC.O qtype=sym infotype=info qcat=news"&gt;INTC.O&lt;/A&gt; on Thursday  canceled plans to introduce its highest-speed desktop computer  chip, ending for now a 25-year run that has seen the speeds of  Intel's microprocessors increase by more than 750 times.