Fibre Channel MCA Interfaces


MCA Fibre Channel interfaces exist from the following manufacturers:

Ancor Communications

The Ancor Fibre Channel Communications Interface Module (CIM) is a 266 megabaud network interface card.


12 August 1996. This adapter is not supported anymore by IBM. The following information will be kept for completeness.


IBM has a Fibre Channel adapter for use in the cluster RISC System/6000 servers. The Fibre Channel adapter/2666 supports Micro Channel bus speeds of up to 80 MB/s. It includes a 4 MByte VRAM buffer.

For details, look at the information from IBM.

Tips on usage


When installing the driver software, it needs to be connected to the switch. When changing the connections to the switch, reboot the RS/6000 afterwards.

High Performance TCP/IP

When using TCP/IP, make sure that some special options are set to use High Performance TCP/IP. The following note helped us at CERN to increase the throughput from 6 to more than 11 MB/s!

RS/6000 workstations are implementing High Performance TCP/IP. The command "no -a" returns informations on the configuration network on a node. If the RFC1323 flag is set to 0, that means High Performance TCP/IP is disabled. To enable it, just turn on the "rfc1323" flag to 1 by using the following command (as a super user):

"no -o RFC1323=1".

But some other parameters need also to be modified. The following list provides one configuration example that is presently working on our workstations:

"no -o sb_max=6000000"
"no -o rfc1323=1"
"no -o thewall=6000"
"no -o lowclust=200"
"no -o mb_cl_hiwat=2000"
"no -o tcp_sendspace=655360"
"no -o tcp_recvspace=655360"
"no -o udp_sendspace=655360"
"no -o udp_recvspace=655360"

There is no need to recompile the kernel nor to reboot the machine. More details concerning the parameter description can be found in the note "Aix_HP_TCP". A copy of the RFC 1323 specification is also available (called "rfc_1323", 85 KB).

Contact: IBM Corp. in Armonk, N.Y. at (800) 426 2255.

CERN - High Speed Interconnect - FCS
Erik van der Bij - 12 August 1996 - Disclaimer