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Commodore C65 System Engineering Design

Updated 26 February 2023

This system engineering overview describes the prototype Commodore C65 system that was being prepared for production in 1991. The Commodore C65 never made it to market, however, prototype systems occasionally come up for sale on auction sites. There are also enthusiast maker projects developing compatible systems to relive what may have been. This article outlines the system engineering design elements for the Commodore C65.


The Commodore C65 is designed to be an entry-level microcomputer designed for the home or student market. The market in the 1990s may still have capacity for an 8-bit microcomputer priced below the 16/32-bit WinTel personal computer range. The Commodore C65 can also support and built on the existing market of microcomputer games and applications already developed in the 1980s, since the introduction of the PET, VIC-20 and C64 microcomputers.

This document is a System Specification that gives a structured description of the Commodore C65 microcomputer in high-level technical terms. This document is considered to be at a preliminary stage to descrive the system for Pilot Production. The enthusiast/maker will need to make changes to the concept design and specifications in order to create a working prototype.

What is a System Engineering Plan?

A system engineering plan for the Commodore C65 would typically outline the technical specifications and requirements for the design and development of the computer system. It would include details on the hardware components such as the processor, memory, storage, input/output devices, and any other necessary peripherals. The plan would also specify the software requirements, including the operating system and any programming languages or applications that would be supported on the system.

The plan would describe the intended use cases for the system and the target market segment, as well as any unique features or capabilities that would differentiate it from other computer systems on the market. It would also include details on the development process, including testing, quality assurance, and compliance with industry standards and regulations.

In the case of the Commodore C65, the system engineering plan would have outlined the technical specifications for the computer, which was intended to be a more advanced and powerful successor to the popular Commodore 64. The C65 was designed to be compatible with the existing software library for the C64, while also offering improved graphics and processing capabilities.

The system engineering plan would have also outlined the intended market for the C65, which was aimed at the home and small business market segments. The plan would have described the unique features of the C65, such as its advanced graphics capabilities and support for multitasking, as well as its compatibility with existing software and peripherals.

Ultimately, while the Commodore C65 never made it to market, the system engineering plan would have provided the blueprint for the development of the system and served as a guide for the engineering team. The plan would have ensured that the technical specifications and requirements for the C65 were clearly defined and that the system was designed to meet the needs of its intended market segment.

Who were the orginal developers of the Commodore C65 engineering specification?

Systems engineering design and technical management was held in house. The following people made significant contributions to this prototype project:

Commodore C65 design outline

This specification describes the requirements for a low-cost 8-bit microcomputer system with excellent graphic capabilities. This section describes the overall Commodore C65 system concept, an overview of the system items, components and general design risks and concerns. It is envisaged that Commodore C65 will become the early 1990 market leaders in entry level microcomputers. This introduction covers the following topics;

System Concept

The C65 microcomputer is a low-cost, versatile, competitive product designed for the international home computer and game market.

The C65 is well suited for first time computer buyers, and provides an excellent upgrade path for owners of the commercially successful C64. The C65 is composed of concepts inherent in the C64 and C128.

The purpose of the C65 is to modernize and revitalize the 10 year old C64 market while still taking advantage of the developed base of C64 software. To accomplish this, the C65 will provide a C64 mode of operation, offering a reasonable degree of C64 software compatibility and a moderate degree of add-on hardware and peripheral compatibility. Compatibility can be sacrificed when it impedes enhanced functionality and expandability, much as the C64 sacrificed VIC-20 compatibility.

It is anticipated that the many features and capabilities of the new c65 mode will quickly attract the attention of developers and consumers alike, thereby revitalizing the low-end home computer market. The C65 incorporates freatures that are normally found on today's more expensive machines, continuing the Commodore tradition of maximizing performance for the price. The C65 will provide many new opportunities for third party software and hardware developers, including telecommunications, video, instrument control (including MIDI), and productivity as well as entertainment software.

Digital Hardware Concept

CPU - Commodore CSG4510 running at 1.02Mhz or 3.5Mhz


Video - Commodore CSG4567 enhanced VIC chip

Audio - Commodore CSG8580 SID chip

Disk, Printer support

External Ports

Keyboard - 77 keys, including standard C64 keyboard plus:

Power supply - external, brick type

C65 System Components

Commodore C65 Block Diagram
diagram  Commodore C65 system block diagram

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