Arapahoe (now PCI Express) is the (strange) name for Intel's new "third-generation" I/O technology for PC's, scheduled to replace PCI-X in 2003 and reach the majority of the desktop/home user market by 2009. This technology was previously named 3GIO for "third-generation I/O", and according to Intel, it will provide the kind of transfer speeds we will be needing when our computers run at 10 GHz or so.
The technology of today which Arapahoe seeks to replace is none other than that of our PCI cards, the add-ons that give more functionality, disk space, or whatever, to our computers. Today's PCI bus, operating at 66 MHz, can transfer a mere 266 Mbytes/second - PCI-X can do little over 1 Gbyte/sec, and it is currently only being used in expensive Compaq servers. HyperTransport, currently about to be rolled out by Advanced Micro Devices, Inc. (AMD) operates at a maximum of 12,8 Gbytes/sec - products based on it are expected in 2002, but the first one, the nForce chipset by nVidia is here already and is already making its way to motherboards.
nForce uses an 800 Mbytes/sec HyperTransport link to send data between its ICP and MCP, the two mainboard components which handle I/O and Multimedia - usually called the Northbridge and Southbridge. The high-speed link gives the nForce significantly higher performance than present-day chipsets by AMD, VIA and ALi.
However, Arapahoe-based products will likely be even faster when it finally arrives - already, Compaq have signed a deal with Intel to make use of the new technology.
A final note: Arapahoe is not, nor is it related to, InfiniBand, another Intel technology designed to provide connectivity between servers and other network devices.