Digital's VAX 4000 Model 100 computer system is the highest performance member of the VAX family of computers. These high-performance systems implement the VAX architecture, continuing complete software compatibility with all other VAX sys- tems. VAX 4000 Model 100 systems are tightly coupled multiprocessing systems comprising of two CPUs that access 128 Mbytes of shared memory. The central processor uses 32-bit architecture with 4 Gbytes of virtual addressing space. The VAX 4000 Model 100CPU features virtual memory management, bootstrap loader, standard instructions for packed decimal, floating (F, D, G, and H data types) and fixed-point arithmetic, character and string manipulations, two 64-Kbyte direct- mapped write-through cache memories, high-precision programmable realtime clock, time-of-year clock with battery backup, and two 16-Kword (144-bit words) writable control stores. The CPU also includes the memory controller and mem- ory battery backup for a full 128 Mbytes of memory capacity. Standard with all VAX 4000 Model 100s is a VAXcluster port, Ethernet port, and two VAXBI channels. The CPU also includes a console subsystem based upon a PDP-11 microcomputer with videoterminal, 30-Mbyte Winchester disk, RX50 floppy disk, and remote diag- nostic port. VAX 4000 Model 100 systems can be ordered with a VMS operating system. VMS provides a reliable, high-performance environment for the concurrent execution of multi- user timesharing, batch, and realtime applications.