Editing HyperTransport (section)

=== Add-on card connector (HTX and HTX3) ===
[[File:HyperTransport16 pcie8riser pcie16.jpg|thumb|Connectors from top to bottom: HTX, PCI-Express for riser card, PCI-Express]]
A connector specification that allows a slot-based peripheral to have direct connection to a microprocessor using a HyperTransport interface was released by the HyperTransport Consortium.  It is known as '''H'''yper'''T'''ransport e'''X'''pansion ('''HTX''').  Using a reversed instance of the same mechanical connector as a 16-lane [[PCI Express]] slot (plus an x1 connector for power pins), HTX allows development of plug-in cards that support direct access to a CPU and [[Direct memory access|DMA]] to the system [[RAM]]. The initial card for this slot was the [[QLogic]] InfiniPath InfiniBand HCA. IBM and [[Hewlett-Packard|HP]], among others, have released HTX compliant systems.

The original HTX standard is limited to 16{{nbsp}}bits and 800{{nbsp}}MHz.<ref>{{cite web |last1=Emberson |first1=David |last2=Holden |first2=Brian |date=December 12, 2007 |title=HTX specification |url=http://www.hypertransport.org/docs/uploads/HTX_Specifications.pdf |website=HyperTransport Consortium |page=4 |access-date=January 30, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20120308085021/http://www.hypertransport.org/docs/uploads/HTX_Specifications.pdf |archive-date=March 8, 2012}}</ref>

In August 2008, the HyperTransport Consortium released HTX3, which extends the clock rate of HTX to 2.6&nbsp;GHz (5.2&nbsp;GT/s, 10.7&nbsp;GTi, 5.2 real GHz data rate, 3&nbsp;MT/s edit rate) and retains backwards compatibility.<ref>{{cite web |last=Emberson |first=David |date=June 25, 2008 |title=HTX3 specification |url=http://www.hypertransport.org/docs/uploads/HTX3_Specifications.pdf |website=HyperTransport Consortium |page=4 |access-date=August 17, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20120308085016/http://www.hypertransport.org/docs/uploads/HTX3_Specifications.pdf |archive-date=March 8, 2012}}</ref>