HP 3000 Manuals HP 3000 Manuals
Overview of Differences: MPE V/E and MPE XL All HP 3000 models run under the Multiprogramming Executive (MPE) operating system, which manages all system resources and coordinates the execution of all programs running on the system. The MPE V/E operating system is designed to run on all HP 3000s except the 900 series. The MPE XL operating system is designed to run on the 900 series. The architecture of the 900 series is based on RISC (Reduced Instruction Set Computer) concepts. Research shows that conventional microcode machines spend about 80% of the time executing about 20% of the instructions. It makes sense, then, to design the computer to directly and quickly implement the most common instructions directly in hardware, instead of supporting bulky microcode. MPE XL is a register-based machine. CPU (central processing unit) registers hold the most frequently used data and instructions. This method requires less chip space and system overhead than microcode. HP-PA accesses files with demand-paged virtual memory. This eliminates the need for code and data segmentation. Disk files are mapped into virtual address space, and file system buffering is no longer needed. MPE XL has two modes: Compatibility Mode (CM) and Native Mode (NM). CM provides backward compatibility with MPE V/E in CM. NM takes full advantage of the 900 Series Hewlett-Packard Precision Architecture (HP-PA). Both are transparent to the user. HP-PA instructions are pipelined. The overlapping execution of multiple instructions for efficiency is made possible by uniform instructions and cycle-time regularity. Optimizing compilers generate efficient object code, allocate registers, and schedule instruction sequences to maintain efficient pipeline operation. New MPE XL features that are not available on MPE V/E include: * Demand-paged virtual memory * Dual programming modes Changed Existing MPE V/E features that have been modified on MPE XL include: * Word size * Priv Mode * Segmenter