The 1108 II, or 1108A, was the first multiprocessor machine in the series, capable of expansion to three CPUs and two IOCs (Input/Output Control Units). To support this, it had up to 262,144 words (four cabinets) of eight-ported main memory: separate instruction and data paths for each CPU, and one path for each IOC. The memory was organized in physical banks of 65,536 words, with separate odd and even ports in each bank. The instruction set was very similar to that of the 1107, but included some additional instructions, including the "Test and Set" instruction for multiprocessor synchronization. Some models of the 1108 implemented the ability to divide words into four nine-bit bytes, allowing use of ASCII characters. Most 1108A configurations included one or two CPUs, each with eight or (optionally) 16 36-bit parallel I/O channels, and two or three 64K core memory cabinets. Three CPU systems, with four core memory cabinets were the exception due to cost considerations. The IOC was a separate cabinet that contained 8 or (optionally) 16 additional I/O channels to support configurations with very large Mass Storage requirements. A very limited number of IOCs were produced, with United Air Lines (UAL) being the primary customer.