HTX Bus

HyperTransport on EATX Motherboards



HTX Bus Description

The HyperTransport eXpansion [HTX interface] is a dedicated expansion slot used on AMD Mother Boards.
HyperTransport eXpansion provides the daughter card with a direct connection to the Motherboards HyperTransport bus, and processor.
HTX was released in 2005, Note that the current version of this standard is called HTX3, which is the same standard with better speed.
The HTX specification places the HyperTransport Interface on a peripheral slot-based card using the same board size as a PCI card.
The current clock speed of an HTX interface [HTX3] runs at 2.6GHz, at a bandwidth of 20.8 GB/s [with 2 unidirectional 16-bit double data rate [DDR] HyperTransport links].
HTX motherboards used the same mechanical connector as PCIe [1x and 16x], although it's rotated. HTX peripheral cards are meant for Servers and Blades.
Also refer to EATX mother board manufacturers.
Extended ATX [EATX] motherboards are used in servers.





HTX 16x PinOut
Pin Side A Connector Side B Connector
# name name
1 RSVD GND
2 VLDT GND
3 GND CADIN8H
4 GND CADIN8L
5 CADIN0H GND
6 CADIN0L GND
7 GND CADIN9H
8 GND CADIN9L
9 CADIN1H GND
10 CADIN1L GND
11 GND RSVD
12 RSVD GND
13 GND CADIN10H
14 GND CADIN10L
15 CADIN2H GND
16 CADIN2L GND
17 GND CADIN11H
18 GND CADIN11L
19 CADIN3H GND
20 CADIN3L GND
21 GND CLKIN1H
22 GND CLKIN1L
23 CLKIN3H GND
24 CLKIN3L GND
25 GND CADIN12H
26 GND CADIN12L
27 CADIN4H GND
28 CADIN4L GND
29 GND CADIN13H
30 GND CADIN13L




All the data and clock signals a differential pairs, and each signal has an associated ground line.


Server boards with HTX interfaces

NetLogic Microsystems {HTX Server boards, Dual AMD Processors}

Supermicro, Inc. {HTX Server boards, Dual/Quad AMD Processors}


HTX Connector and Form Factor Specification for HyperTransport Daughtercards and EATX Motherboards;
HyperTransport Consortium [www.hypertransport.org]


PC motherboard
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Modified 1/11/12
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