Tom, The UCM was an older controller whose I/O can be attached (migrated) to a CP270. As far as FCM loading is concerned, you can improve overall I/O response by using more FCMs per ZCP. You can improve if further by ordering the ECBs for the FCMs properly in the _ECB compound. When the ZCP wants I/O, it sends messages to the FCMs that hold that I/O in the order that their ECBs appear in the _ECB compound. It then calculates how long it should wait for the first FCM to gather its I/O and then asks for it. If the FCM is finished gathering, the ZCP gets the data and moves to the next FCM. If the FCM is busy, the ZCP sits backs and waits a bit more before asking again. This cycle is repeated as necessary. Since the FCMs are queried in parallel, the more of them you have the more parallel processing can be achieved and the less the ZCP has to wait for its data. Also, as you might have realized, this means that FCMs with short FBM chains should be place higher on the list of ECBs in the _ECB compound. This allows the ZCP to wait a shorter time to get that data. Since the other FCMs are processing in parallel, it is increasingly likely that they will be ready if they are listed in increasing chain length. Does this make some sense? Regards, Alex Johnson Invensys Process Systems 10900 Equity Drive Houston, TX 77041 713 329 8472 (desk) 713 329 1600 (operator) 713 329 1944 (SSC Fax) 713 329 1700 (Central Fax) alex.johnson@xxxxxxxxxxxxxxxx * Confidentiality Notice: This e-mail and any associated files are intended solely for the individual or entity to whom they are addressed. Please do not copy it or use it for any purposes, or disclose its contents to any other person. Further, this e-mail and any associated files may be confidential and further may be legally privileged. This email is from the Invensys Process Systems business unit of Invensys plc which is a company registered in England and Wales with its registered office at Portland House, Bressenden Place, London, SW1E 5BF (Registered number 166023). For a list of European legal entities within the Invensys Process Systems business group, please click here http://www.invensys.com/legal/default.asp?top_nav_id=77&nav_id=80&prev_id=77. If you have received this e-mail in error, you are on notice of its status. Please notify us immediately by reply e-mail and then delete this message from your system. Thank you for your co-operation. You may contact our Helpdesk on +44 (0)20 7821 3859 / 2105 or email inet.hqhelpdesk@xxxxxxxxxxxxx This e-mail and any attachments thereto may be subject to the terms of any agreements between Invensys (and/or its subsidiaries and affiliates) and the recipient (and/or its subsidiaries and affiliates). _______________________________________________________________________ This mailing list is neither sponsored nor endorsed by Invensys Process Systems (formerly The Foxboro Company). Use the info you obtain here at your own risks. Read http://www.thecassandraproject.org/disclaimer.html foxboro mailing list: //www.freelists.org/list/foxboro to subscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=join to unsubscribe: mailto:foxboro-request@xxxxxxxxxxxxx?subject=leave