A cluster tool is a single integrated processing tool which incorporates two or more process modules. Further, in an open cluster tool, the process modules may not all be supplied by the same vendor. This article is aimed at equipment vendors/suppliers faced with revising their control systems to meet the requirements for communications in an open cluster tool. Standards for these communications are being developed by the SEMI's MESC committee  (see Table 1 for a full list of acronyms used in this article). One goal of the cluster tool movement is to allow the equipment vendor to focus on their process. MESC (formerly MESA) has developed mechanical and utilities standards that are fairly well developed and reasonably simple. The proposed communications standards, on the other hand, seem neither complete nor simple. So what's going on! The fact is that the problem is complex. The cluster tool is itself a mini factory. The problem therefore is analogous to General Motor's MAP which defines communications and control required by an entire factory. The guiding principle has been to reference existing standards, rather than invent new ones, to allow equipment vendors to purchase off-the-shelf hardware and software for faster development, higher performance and better reliability. That is easy to say but equipment suppliers are still faced with supplying a control system that is compatible with open architecture cluster tools. Few have the luxury to scrap what they have and start afresh. Worse yet, cluster tool compatibility is, as yet, not well defined or understood. This article is intended to provide information to ease the burden on the equipment supplier in the transition toward full open architecture cluster tools. First of all the status of the current standards will be reviewed. This is followed by what you might look for in the way of off-the-shelf control and networking software. Finally the thorny issue of "how do you get there from here?" will be addressed.