Quintupling the speed of the PDP-8 DF32 disk system for real-time use

The author has noted some inefficiencies in the operation of the DF32 hardware/software disk system on the PDP-8. While such inefficiencies are not significant when the disk is used only as a store for programs which are called into core from the keyboard, they become important when the disk is used as a real-time backup for core. This paper isolates some of the problems, gives rules for avoiding them, and then describes how the system software was modified to obey these rules. The speed of the modified system is noticeable even when SAVEing and CALLing programs from the keyboard; successive blocks can be transferred between disk and core in one-fifth the previously required time.