In the design of a large high-speed computer, the size of the system leads to long cable delays for data transmitted between different parts of the machine. This problem and the interconnexion of a high-speed e.c.l. circuit family are discussed, and comment is made on future lines of development for technology in high-speed computers.Priority circuits in a large asynchronous system also present difficulties not usually encountered in smaller machines and a discussion of how these difficulties arise is presented.