The P1 computer

Back in the early 80’s I built a computer based on a kit from the Eindhoven Computer Association. Although bits of hardware and all documentation and software have been lost, I am slowly restoring this machine to its deserved status.

This computer was called the P1, an informal play on the naming scheme used by Philips for their business computers: ‘P’ followed by a number (as in their P5300, and later the iconic P2000).

The main board of the P1 is a close copy of the board created and sold by Central Data.

I created a bus to add extra memory, a serial IO port, a floppy disk interface and a drum sound generator. The original hardware is lost. In my restoration I had to create a daughterboard (the small brown board in the photo below) containing replacement PROMs and static RAM.

One difference between the Central Data machine and the P1 is that the P1 uses not one but two character generator PROMs, and displays full ASCII characters (upper and lower case). This is slightly annoying as the Central Data machines uses values 00 to 1F for upper case characters. All routines that write to the screen therefore have to be modified.