The MSMQ-MQSeries Bridge, which ships with Host Integration Server 2006 (HIS 2006) and earlier, is a well-established way to integrate the messaging worlds of Microsoft and IBM.

The Bridge is essentially a Windows application written to use the MQSeries (or more accurately WebSphere MQ) APIs to manage message flow to and from IBM hosts (that is, mainframes or servers running Windows, Solaris, Linux, etc.). Messages can be pulled from local MSMQ queues and sent through the MQSeries client to remote MQSeries queues, or pulled from those same remote MQSeries queues and placed in the local MSMQ queues.

Being dependent on the WebSphere MQ client, the Bridge can only be installed on operating systems where there could be a Windows client to work with. For example, IBM does not currently supply a true 64-bit client for Windows so HIS 2006 will not provide the option to select the Bridge when setup is run on 64-bit operating systems. (Note: setup detects the operating system and not the presence of the WebSphere MQ client so the introduction of a true 64-bit client will not cause setup to do anything different).

According to:

System Requirements for WebSphere MQ 6.0 Windows 

    1. WebSphere MQ V6 64-bit Windows (toleration) support:
      - WebSphere MQ V6 64-bit Windows (toleration) is applicable at WebSphere MQ V6.0.2.1 or later.
      - WebSphere MQ V6.0.2.0 or lower versions only support 32-bit operating systems.
      - Only 32-bit versions of programming languages are supported.

 and

939202 An update is available that enables you to install the client-based BizTalk Adapter for WebSphere MQ on 64-bit versions of Windows

"Starting with version 6.0.2.1, WebSphere MQ for Windows is also supported as a 32-bit application on 64-bit versions of Windows."

it is possible to install the more recent WebSphere MQ clients on 64-bit Windows but they cannot be treated as 64-bit applications.

So, in summary, if you wish to integrate MSMQ with WebSphere MQ using HIS 2006's Bridge then you need to test and deploy on x86 operating systems.

[[24th March, 2009 - Host Integration Server 2009 will not be adding 64-bit support for the MSMQ-MQSeries Bridge. The requirement to deploy on x86 operating systems still stands.]]