The P1 restoration project

PHCC-2 board This site describes the project to restore my ancient 2650-based computer that I call the "P1".

The 2650 microprocessor is an 8-bit microprocessor from Signetics from the late '70s and early '80s. Several companies sold boards using this processor, including Central Data. I obtained a modified copy of the Central Data board in 1980 or 1981. The board is marked "PHCC-2", and has slight modifications from the original board. Eventually I expanded this board with a printer interface, a 32 KByte RAM card, a floppy controller and two 5 1/4" floppy drives. I used the P1 computer for simple word processing and for programming in assembler, Basic, Pascal and Forth. I also added an interface to a box of electronics to create drum sounds, with a simple notation and program to convert sheet music to sound. It has been sitting in my attic after I bought a IBM PC clone. Recently I decided to restore this old bit of history to its former glory, although some of the hardware and all of its software have been lost.

Current contents on this site:

Printed circuit boards: Schematics of the Central Data and PHCC boards.
asm2650: Assembler for the Signetics 2650 processor.
P1 bus signals: Description of the bus/backplane signals used on the P1. The bus is based on the Phunsy bus, so that I could easily use the floppy controller and 32K dynamic RAM card developed for the Phunsy.
PROM replacement: An modern alternative for the PROMs on the P1 board.
Static RAM addition: An modern alternative to the original 32K dynamic RAM card.
Floppy disk drive controller: The original controller for 5.25" single density floppy drives. I do not know the origin of this card, but I reverse engineered the schematics for it.
Developing programs for the P1: Descriptions and downloads of various tools that I created to facilitate the development of programs, including a tool to covert binaries to audio that can be used instead of a cassette tape drive.
Disk Operating System: I finally got the hardware to work reliably. Now it is time to turn to the software, beginning with the basis: a Disk Operating System.
Popmon monitor program: Description of the monitor used by the P1.

Contact me

Eelco Vriezekolk

Questions or remarks? Send me an email on eelco[at-sign]ztpe[little dot]nl