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.
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