USB enabled PDP8 computer

The PDP-8 family of minicomputers was built by Digital Equipment Corporation between 1965 and 1990. The PDP8 computers were one of the first computers that were affordable by a broader range of customers; that contributed in the success of these machines. In 1976, Intersil developed a PDP8 chipset consisting of the IM6100 processor [4], the I/O extension (IM6101) and the UART (IM6402). The PDP8 utilizes a small instruction set. Only eight basic instructions are implemented, which provide enough functionality to compose complete programs. Since there are many PDP8 legacy programs available on paper and magnetic tapes and not that many operational PDP8 machines left, the PDP8 project was initiated. The Intersil chipset is used together with a 80C32 microcomputer in a single board device. The PDP8 device enables the usage of a real PDP8 computer as in the days around 1970, including native I/O connectivity. In addition, the PDP8 device is controlled by a host computer. Original PDP8 peripherals such as teleprinters and magnetic tape readers can be connected to the PDP8 device. In this way original PDP8 programs stored on paper or magnetic tapes can be loaded and executed into the PDP8 device. The 80C32 has control over the memory and the system state of the PDP8 processor. The 80C32 communicates with the host computer via USB connection. The USB connection is implemented by the PDIUSB12 controller from Philips. The whole PDP8 device is under control of a dedicated application running on a Microsoft Windows host computer. A command/response interface between the host and the PDP8 device was developed for this purpose and implemented. This article describes the development process and the design of the PDP8 device hardware, the device software and the host software.