Commodore C65 system engineering specification and technical overview

Introduction

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:

Fred Bowen - System Software - C65
Paul Lassa - Hardware Engineer - C65, DMAgic
Bill Gardei - LSI engineer - 4567, FDC
Victor Andrade - LSI engineer - 4510
Included are contributions by contractors hired by Commodore for the C65 project. These contributions include the DOS, Graphics, Audio, and Memory management areas.

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
System overview
System components
System concerns
System maps

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

New instructions, including Rockwell and GTE extensions
Memory Mapper supporting up to 1 Megabyte address space
R6511-type UART (3-wire RS-232) device, programmable baud rate (50-56K baud, MIDI-capable) , parity, word size, sync and async. modes. XD/RD wire ORed/ANDed with user port
Two CSG6526-type CIA devices, each, with 2 I/O ports, programmable TOD clocks, interval timers, interrupt control

Memory

RAM - 128Kb (DRAM)
Externally expandable from additional 512K bytes to 4MB using dedicated RAM expansion port.
RAM - 128Kb
C64 Kernel and BASIC 2.
C65 Kernel, Editor, BASIC 10.0, ML Monitor (like C128)
DOS v1O- (1581 subset)
Multiple character sets: 40 and 80 column versions
National keyboards/charsets for foreign language systems
Externally expandable by conventional C64 ROM cartridges via cartridge/expansion port using C64 decodes
Externally expandable by additional 128K bytes or more via cartridge/expansion port using new system decodes
DMA - Custom DMAgic controller chip built-in
Absolute address access to entire 8MB system map, including I/O devices, both ROM & RAM expansion ports
List-based DMA structures, can be chained together
Copy (up, down, invert), Fill, Swap, Mix (boolean Minterms) Hold, Modulus (window), Interrupt, and Resume modes
Block operations from 1 byte to 64K bytes
DRQ handshaking for I/O devices
Built-in support for (optional) expansion RAM controller

Video - Commodore CSG4567 enhanced VIC chip

RGBA with sync on all colors or digital sync
Composite NTSC or PAL video, separate chroma/luma
Composite NTSC or PAL digital monochrome
RF TV output via NTSC or PAL modulator
Digital foreground/background control (genlock)
All original C64 video modes:
     40x25 standard character mode
     Extended background color mode
     320x200 bitmap mode
     Multi-color mode
     16 colors
     8 sprites, 24x21
40 and 80 character columns by 25 rows: Color, blink, bold, inverse video, underline attributes
True bitplane graphics:
     320 X 200 X 256 (8-bitplane) non-interlaced
     64 X 200 X 16* (4-bitplane) non-interlaced
     1280 X 200 X 4* (2-bitplane) non-interlaced
     320 X 400 X 256 (8-bitplane) interlaced
     640 X 400 X 16* (4-bitplane) interlace
     1280 X 400 X 4* (2-bitplane) interlace
          *plus sprite and border colors
Color palettes:
     Standard 16-color C64 ROM palette
     Programmable 256-color RAM palette, with
     16 intensity levels per primary color (yeilding 4096 colors)
Horizontal and vertical screen positioning verniers
Display Address Translator (DAT) allows programmer to access bitplanes easily and directly.
Access to optional expansion RAM
Operates at either clock speed without blanking

Audio - Commodore CSG8580 SID chip

Stereo SID chips:
     Total of 6 voices, 3 per channel
     Programmable ADSR envelope for each voice
     Filter, modulation, audio inputs, potentiometer
     Separate left/right volume, filter, modulation control

Disk, Printer support

FDC custom MFM controller chip built in, with 512-byte buffer, sector or full track read/write/format, LED and motor control, copy protection.
Built-in 3.5" double sided, 1MB MFM capacity drive
Media & file system compatible with 1581 disk drive
Supports one additional "dumb" drive externally
Standard CBM bus serial (all modes, about 4800 baud)
Fast serial bus (C65 mode only, about 20K baud)
Burst serial (C65 mode only, about 50K baud)

External Ports