The Ulti-PET

The Ulti-PET is a re-incarnation of the Commodore PET computer(s) from the later 1970s. It is currently build on a multiple Eurocard board and has only parts that can still be obtained new in 2021-2023. It is re-using various technologies from the Micro-PET, the CS/A computer, and others. Currently it is a work-in-progress.

The goal is to combine multiple of these boards into a single PCB that fits a (slightly modified) C64 case. This board is currently in the design phase.

Note that I now call it "Ulti-PET" to avoid confusion with Gideon's Ultimate projects.

News:

2024-02-03 Clarification on the goal of integrating into a single PCB and the components.
2023-12-13 Update to 1.3C that is using an FPGA and has many more features, like graphics features, or DAC output via DMA.
2023-01-08 The Ultimate PET introduced

Overview

After building the Micro-PET I noticed, that for further features, I would have to get larger than a Euro-card. The challenge - for me at least - is that I use an older, private-use restricted version of Eagle that can only do Euro-card PCBs, but not larger.

So, the current version is based on multiple Euro-PCBs, but will eventually be combined into a single PCB.

The main development is happening on github (see link left in the menu).

Features

Here is a list of the features. Most of them have been implemented in the Eurocard version already, and only need to be combined into the single PCB:

Ulti-PET features

Commodore 3032 / 4032 / 8032 / 8296 with options menu to select at boot

Boot-menu to select different PET versions to run
40 col character display
80 col character display
8296 memory map emulation
IEEE488 interface (via PETIO board)
Tape connector (pin, via PETIO board)
PET graphics keyboard, or alternatively a C64 keyboard

Improved system design:

512k video RAM, 512k fast RAM accessible using banks on the W65816 CPU
boot from an SPI Flash ROM
up to 12.5 MHz mode (via configuration register)
VGA Colour video output (RGBI in 640x480)
Write protection for the PET ROMs once copied to RAM
lower 32k RAM mappable from all of the 512k fast RAM

Improved Video output:

Multiple colour modes (Colour-PET, C128-VDC-compatible, Multicolour)
Colour Hires graphics mode
Modifyable character set
40/80 column display switchable
25/50 rows display switch
multiple video pages mappable to $8000 video mem address

Audio output:

DMA engine to play audio samples on stereo DAC sound output
Dual-SID

Extra I/O features on top

Colour-PET compatibility (as defined by Steve Gray's colour-PET project)
RS232 interface
Fast serial IEC bus (like in the C128)
Both IEEE488 and IEC bus are capable of being used as device for another computer (ATNA capability)
An extra 8-bit I/O port in addition to the Userport
Simpler and more versatile system bus (using the Ultra-BUS backplane:

CS/A bus (my standard)
Some Apple-II bus compatibility
RC2014 bus connectors

Extensions planned on the combined board:

(Built-in disk drive simulator (e.g. nano488 or pico488) - Cancelled due to space restrictions
Built-in Userport extensions, like Joystick ports

As mentioned, the current design uses multiple PCBs, esp. the Ultra-CPU and the Ultra-Bus. The Ultra-CPU, Ultra-Bus and the existing CS/A PETIO board already make up a Colour-PET clone.

Gallery

Some pictures of the current state of the Ultra-PET

An Ultra-CPU Euro-PCB board, with visible 65816 and the large SMD CPLD. Two memory chips with 512kB each, one for main operation, one for the video output;

The Ultra-CPU and PETIO boards on an Ultra-Bus backplane

A screenshot demonstrating graphics features

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Last modified: 2024-02-03