Fact-checked by Grok 2 weeks ago

Commodore 65

The , also known as the C65 or C64DX, was an unreleased prototype 8-bit home computer developed by as a successor to the highly successful Commodore 64. Intended to blend with the C64 through an mode, it incorporated advanced features aimed at rivaling the graphics and sound capabilities of 16-bit systems like the while remaining affordable for first-time buyers and gamers. Development began in 1989, with prototypes emerging by 1991 and an estimated 200 units produced before the project was canceled in the early 1990s due to Commodore's financial struggles, culminating in the company's in 1994. Key hardware innovations included a CSG 4510 processor—a customized version of the MOS 6502 running at 3.54 MHz, approximately 3.5 times faster than the C64's 1 MHz CPU—and 128 KB of base RAM expandable to 8 MB via an external . The video subsystem featured the CSG 4569 VIC-III chip, supporting six graphics modes with resolutions ranging from 320×200 to 1280×400 pixels, an 80-column text mode, and a palette of 4096 colors for enhanced visual fidelity. Audio was powered by two CSG 8580 chips, enabling six-voice stereo sound, while connectivity options encompassed dual /mouse ports, a serial bus, RGBI video output, and a built-in 3.5-inch double-density floppy compatible with the 1581 model. The system also included a full-sized 77-key keyboard with 12 function keys and a cursor pad, 128 KB of ROM, and various expansion ports, positioning it as a versatile machine for gaming, productivity, and emerging markets in regions like . Although never commercialized—potentially priced under $499—the C65's design influenced later retrocomputing projects, such as the open-source MEGA65 recreation.

Development

Origins and planning

By the late 1980s, faced intensifying competition in the personal computer market, where the once-dominant Commodore 64 (C64) was experiencing slowing sales growth despite having sold over 10 million units by 1987. The rise of 16-bit systems, including Commodore's own line, the Atari ST, and increasingly affordable PC compatibles, threatened the 8-bit segment's viability, prompting the company to seek ways to prolong the C64's lifecycle while appealing to budget-conscious first-time buyers and existing users. The Commodore 65 project, initially conceived as the "C64DX" in 1987-1988, emerged as a strategic response to these pressures, aiming to deliver an enhanced successor that retained the C64's affordability and massive software library. Development formally ramped up in under the guidance of a small team of engineers, including Fred Bowen for system software and enhancements, Paul Lassa for hardware, Bill Gardei for , and Victor Andrade for CPU design, with support from contractors and the Semiconductor Group (CSG) team working on custom chipsets. The core objectives centered on full with C64 software through an mode, integration of a built-in 3.5-inch floppy drive to simplify peripherals, and upgraded capabilities designed to approach Amiga-level without abandoning the 8-bit . Additionally, the project included plans for 10.0, an advanced iteration of the language featuring elements and improved I/O handling to empower users and developers. Planning emphasized cost control to target entry-level pricing around $350-499, positioning the C65 as an accessible for the home and education markets while extending Commodore's hold on the 8-bit ecosystem. The targeted release was set for 1990, aligning with holiday buying seasons to capitalize on renewed interest in affordable amid the transition to more powerful systems. Early design decisions focused on balancing with , such as incorporating a CSG 4510 processor running at approximately 3.54 MHz to support enhanced multitasking without alienating the C64's vast user base.

Prototyping and testing

The prototyping phase of the Commodore 65 began in 1989, following initial planning efforts to create a backward-compatible successor to the Commodore 64, with the design formalized that year by the Semiconductor Group (CSG). By 1990, the first hardware prototypes emerged, including early Revision 2A circuit boards that integrated custom CSG chips such as the 4510 CPU and 4567 video controller. These were followed by Revision 2B motherboards in 1991, which refined the layout for better stability and incorporated a built-in 3.5-inch double-density floppy drive compatible with the Commodore 1581 format. Approximately 50 to 200 units were produced for internal testing and purposes, with some sources estimating up to 1,000 based on leaked inventory after Commodore's , though operational examples remain extremely rare. These prototypes featured a custom plastic case design intended for consumer appeal, including integrated ports and drive bays, alongside early implementations of enhanced graphics and dual chips for audio output. Testing focused on integration, such as the CSG 4562 for advanced video modes and the dual 8580 synthesizers for 6-voice sound capabilities. Key challenges during testing included software instability in the onboard 10.0 interpreter, which was incomplete with missing commands and functions like , leading to frequent syntax errors and limited programmability. Hardware issues arose with the output, which was partially implemented and prone to signal instability, restricting reliable video display in early demos. Stereo sound integration also faced hurdles, as the dual setup required precise synchronization that was not fully optimized in Revision 2A boards, resulting in occasional audio glitches during playback tests. Internal demonstrations showcased preliminary graphics capabilities, such as hardware sprites and high-resolution modes, to evaluate compatibility with Commodore 64 software.

Hardware

Processor and memory management

The Commodore 65's central processing unit (CPU) was the MOS Technology CSG 4510, a custom 8-bit microcontroller that served as an enhanced variant of the 65CE02, itself an evolution of the original MOS 6502 processor family. This integration combined the 65CE02 core with additional peripherals, including two MOS 6526 Complex Interface Adapters (CIAs) for I/O handling, four 16-bit interval timers, two 24-hour clocks with alarms, a full-duplex UART, shift registers, and 30 programmable I/O lines, all within a single 84-pin package fabricated in low-power 2U CMOS double-metal technology. In native mode, the CSG 4510 operated at a clock speed of 3.54 MHz, providing significantly faster performance than the Commodore 64's 1 MHz 6510 CPU, while a compatibility mode reduced the speed to 1 MHz to ensure seamless execution of C64 software. The instruction set of the CSG 4510 built upon the 65CE02's extensions to the 6502 , incorporating additional opcodes for improved and efficiency, such as bit test and branch instructions (BBR and BBS), bit reset and set (RMB and SMB), transfer and test bits (TRB and TSB), and optimizations that allowed one-byte instructions to complete in a single cycle. These enhancements enabled faster execution of common operations, including bit-level addressing and conditional branching, reducing overhead in system-level programming compared to the baseline 6502's more limited set. The design emphasized full static operation for reliability in low-power environments, supporting the 65's goal of integration in cost-sensitive home computing systems. Memory management in the Commodore 65 centered on a 128 base RAM configuration, divided into two 64 segments: one dedicated to the CPU for general-purpose access and the other allocated for I/O devices and video operations. An integrated (MMU) within the CSG 4510, supplemented by external expansion, facilitated access up to 8 MB through 64 addressable banking, utilizing a 24-bit to map larger memory regions without the performance penalties of traditional paging mechanisms. This banking allowed direct access to extended RAM via external slots, enabling developers to run larger programs while maintaining with the 64 logical of legacy 6502 software. The overall low-power of the CSG 4510 further supported efficient handling in integrated systems, minimizing draw during banking switches and I/O interactions.

Graphics capabilities

The graphics subsystem of the Commodore 65 centers on the VIC-III video controller chip, designated CSG 4567 and nicknamed the "Bill" chip after its designer Bill Gardei. This chip supersets the functionality of the VIC-II from the Commodore 64, maintaining full with legacy display modes such as 40×25 text, 320×200 multicolour bitmap, extended colour text, and support for eight 24×21-pixel hardware sprites with features like expansion, priority, and . Beyond compatibility, the VIC-III enables advanced bitplane graphics modes for higher resolution and color depth. Non-interlaced options include 320×200 at 256 colors (using eight bitplanes), 640×200 at 16 colors (four bitplanes), and 1280×200 at 4 colors (two time-multiplexed bitplanes). Interlaced modes double the vertical resolution to 400 lines while retaining the same color depths, with hardware support for scrolling, external synchronization (genlock), and character attributes such as blink, bold, underline, and reverse in 80×25 text mode. The system supports a 12-bit RGB color palette of 4096 colors ( intensity levels per primary), with 256 programmable entries accessible via palette at addresses D100–D3FF for direct mapping of bitplane indices to on-screen hues in high-color modes. Video banking allows for character-based modes or for 640-pixel operations, facilitating efficient access across the 128 . Graphics acceleration is provided by the DMAgic controller (CSG 4151), a dedicated chip that doubles as a for hardware-assisted tasks, including block copies (with inversion and direction options), fills, line drawing, and mixing operations between source, destination, and pattern data. This offloads the CPU, enabling faster rendering in native C65 applications. Output options encompass analog RGB with , separate luma/ signals for , digital monochrome, and provisions for an , available in both and PAL variants to suit regional standards.

Audio features

The Commodore 65's audio subsystem was centered around two 8580 (Sound Interface Device) chips, also known as Sydney II, which provided true capabilities as a significant upgrade from the mono audio of the Commodore 64. Each 8580 chip supported three independent voices, yielding a total of six voices across the stereo channels (three per channel). The SID chips offered versatile sound generation features, including four waveforms per voice—triangle, sawtooth, variable pulse-width, and pseudo-random noise—along with programmable ADSR (attack, decay, sustain, release) generators for dynamic sound shaping. Additional capabilities encompassed a three-mode resonant (low-pass, band-pass, high-pass) with programmable and , as well as 8-bit digital-to-analog conversion for volume control on each voice and a master volume. These features enabled high-fidelity and effects, including digital sample playback through the chips' 4 kHz . Over the Commodore 64's single 6581 , the dual 8580 configuration delivered true stereo separation by allowing independent panning of voices between left and right channels, improved audio clarity from the CMOS-based 8580's and reduced analog distortion, and support for software mixing techniques to simulate spatial or audio effects. The 8580's design also facilitated cleaner stereo output without the analog issues of earlier NMOS SID variants. Audio output was handled via dedicated left and right jacks on the rear panel, enabling direct connection to stereo amplifiers or televisions. The system maintained backward compatibility with 64 music and sound routines, leveraging the identical register interface for seamless playback of existing software.

Ports and expansion

The 65 featured a range of standard ports designed for compatibility with existing peripherals while supporting enhanced functionality. It included two DE-9 ports on the side, compatible with standard Atari-style joysticks and paddles, as well as support for lightpens and other analog controllers through these interfaces. A 24-pin user was provided for connections, enabling compatibility with modems like the Commodore 1670 and serial devices. Additionally, a 6-pin IEC allowed attachment of peripherals such as disk drives (e.g., 1541, 1571, 1581) and printers, operating at approximately 4800 in standard mode. For video and audio outputs, the system offered an 8-pin for and audio, an 8-pin DIN RGB port identical to the for high-quality analog RGBI signals, and an jack intended for direct TV connection in or PAL formats. However, the RF output remained non-functional in known prototypes due to incomplete development of the modulator circuitry. Separate left and right stereo audio jacks were also included to leverage the system's dual audio chips. Expansion options emphasized modularity and . A 50-pin cartridge port on the rear supported cartridges and additional , accommodating both new C65-specific expansions (up to 128 or more) and adapted C64 cartridges via an optional 44-to-50-pin . A dedicated 30-pin expansion slot allowed external upgrades from the base 128 to a maximum of 8 MB, using a expansion controller for bank selection and integration with the system's . An internal bus connected the custom floppy controller, facilitating direct integration with the built-in drive and potential for additional storage controllers. The Commodore 65 incorporated built-in storage via an integrated 3.5-inch double-sided floppy drive, utilizing a custom F011 controller (CSG 4165) with a 512-byte buffer for efficient data handling. This drive supported a formatted capacity of 880 KB in double-density mode, compatible with 1581 disk formats and file systems, and included features like timed head stepping and multiple read recovery methods. Planned peripherals extended the system's versatility, with support implemented through the DE-9 joystick ports using relative positioning and button inputs for up to three-button devices. Modem compatibility was enabled via the user port, supporting protocols with configurable rates up to 56,000 bps. An 8-pin Mini-DIN port was designated for connecting additional external floppy drives, such as the unreleased model, to expand storage options.

Software

Operating system

The Commodore 65 featured a ROM-based operating system centered around 10.0, an enhanced iteration of Commodore's designed to leverage the system's advanced hardware capabilities. Upon startup, the OS initializes from a 128 KB that includes the , ROM, , and components, automatically loading 10.0 into the available 128 KB of for immediate user interaction. This boot process prioritizes native C65 mode, performing hardware checks such as detecting the internal 1565 floppy drive before presenting the READY prompt. BASIC 10.0 introduced numerous extensions over earlier versions like BASIC 2.0 on the Commodore 64, incorporating new commands tailored for graphics, sound, and file operations while supporting elements of through improved program flow controls. Graphics-specific commands included GRAPHIC for configuring bitplane modes (such as 320x200 with 256 colors), for -accelerated drawing operations, PALETTE for defining colors from a 4096-color palette, and for direct memory access tasks. Sound commands enabled control over the dual SID chips, while file handling was augmented with TYPE for displaying sequential files and enhanced wildcard support in DOS commands like DIR for disk catalogs. Additional utilities encompassed an on-screen editor with function keys (e.g., F1 for 40/80-column toggling, F3/F4 for directory listings, F8 for entering the machine language monitor), FIND and CHANGE for editing programs, and FRE variants (FRE(0), FRE(1), FRE(2)) to report memory usage across program, variables, and expansion banks. Error handling saw improvements, with specific messages like ?UNIMPLEMENTED COMMAND ERROR for incomplete features, surpassing the more generic errors in BASIC 2.0. The interpreter also integrated built-in Commodore DOS for floppy disk operations, supporting the 1581-format internal drive and up to two drives total via an IEEE-8250-based system with better pattern matching for file searches. In prototype units, the operating system remained incomplete, with several advanced commands—such as for filling shapes, LOCATE for cursor positioning, and for graphics resizing—triggering errors due to unfinished implementation. Bugs affected features like wildcard directory listings and certain sound commands, reflecting the project's abrupt cancellation in 1991 before full stabilization. Despite these issues, the OS demonstrated potential for a more sophisticated programming environment, emphasizing direct hardware access without requiring for complex tasks.

Compatibility modes

The Commodore 65 incorporated dedicated compatibility modes to support the extensive Commodore 64 software library, enabling users to run legacy applications without modification on the upgraded hardware. In C64 mode, the system restricted access to 64 KB of RAM and standard input/output configurations to mimic the original Commodore 64 environment, while native C65 mode unlocked the full 128 KB RAM, faster processing, and enhanced features. This dual-mode approach was facilitated by the operating system's , which included both C65 extensions and a C64-compatible interpreter. Hardware-level emulation ensured close adherence to Commodore 64 behavior. The CSG 4510 processor, a variant of the 65CE02, operated at 1 MHz in C64 mode—downclocked from its native 3.54 MHz speed—using "dead cycles" to replicate the original 6510's timing precisely. The VIC-III (CSG 4567) chip emulated the VIC-II graphics controller, supporting standard resolutions like 320×200 pixels and 40×25 text modes while disabling advanced C65 capabilities such as 4096-color palettes or higher resolutions. For audio, the dual CSG 8580R5 chips provided passthrough functionality, routing mono C64 sound signals through one chip to deliver exact waveform reproduction without stereo enhancements. Software switching between modes was handled through commands or automatic detection, such as into C64 mode if a required it or pressing the C= key; the ROM was largely identical to the C64's with patches for serial bus routines and initialization to prioritize C65 features unless overridden. Despite these efforts, compatibility was not absolute, with estimates placing it at around 75-80% for the C64 library. Limitations arose from the 65's (MMU) and banking mechanisms, which could conflict with C64 programs relying on undocumented access, illegal opcodes, or precise timing—such as fast loaders and copy-protection schemes. Expanded beyond 64 occasionally interfered, requiring software workarounds in some cases. Prototypes demonstrated practical viability, with testing by engineers like Riccardo Rubini showing successful execution of numerous C64 games and demos in across board revisions, including firmware versions 910111 and 911001. This confirmed the mode's reliability for mainstream titles, though edge cases highlighted the need for further refinement. The primary benefit of these modes was preserving access to the Commodore 64's vast ecosystem of over 10,000 commercial and public-domain titles, extending their lifespan on a more powerful platform without necessitating rewrites and easing the transition for users and developers.

Cancellation and aftermath

Reasons for cancellation

The Commodore 65 project encountered significant technical delays due to unresolved issues in key components, including the incomplete finalization of BASIC 10.0, the absence of a functional for video output, and persistent debugging problems with the stereo sound implementation via the dual SID chips. Prototypes, numbering around 205 units, also suffered from overheating and incomplete hardware integration, such as reliance on a single SID chip in early revisions despite plans for stereo audio. These shortcomings stemmed from a small development team and bugs in test chips for the CSG 4510 processor and associated graphics hardware, which hindered reliable C64 compatibility and overall stability. Timeline pressures exacerbated these challenges, as the project missed its targeted Christmas 1990 release window, originally set for season to capitalize on C64 sales momentum. Further delays pushed potential availability into 1991 and then early 1992, with prototypes still exhibiting timing issues and software incompatibilities by mid-1991. The diversion of engineering resources to the rushed (C64GS) console during summer 1990 further stalled progress on the C65, as the stopgap project repurposed C64 hardware without advancing the more ambitious 8-bit upgrade. Corporate factors played a pivotal role, as Commodore's mounting financial struggles in the late 1980s and early 1990s led to understaffed teams and deprioritization of 8-bit initiatives in favor of 16-bit development, such as the Amiga 600. Chairman Irving Gould's leadership emphasized short-term profitability over long-term innovation, resulting in low priority for the C65 amid broader company-wide cost-cutting. Market analysis revealed declining demand for 8-bit systems, with rising competition from PCs, consoles, and 16-bit platforms like the eroding the C64's dominance; North American sales teams lost interest, viewing the prototypes as unprofitable in a shifting . Although C64 sales remained strong at 250,000 units in the UK in 1990, the overall 8-bit market contraction made further investment in upgrades like the C65 untenable. The project was ultimately scrapped in early 1991, after resources had been diverted to the C64GS—a console variant that sold approximately 20,000 of 80,000 planned units and failed commercially. This decision reflected Commodore's strategic pivot away from 8-bit enhancements, sealing the C65's fate as an unrealized prototype amid accelerating corporate decline.

Immediate consequences

The diversion of the Commodore 65 development team in summer 1990 to produce the C64 Games System (C64GS), a console variant of the Commodore 64 aimed at competing in the emerging games market, stalled progress on the more advanced project. This reallocation resulted in the manufacture of around 20,000 C64GS units at factory by late 1990. Despite initial European distribution, the system sold fewer than 20,000 units and was discontinued by mid-1991, with unsold stock repurposed for standard C64 sales, marking another failed pivot in Commodore's console efforts. Approximately 200 C65 prototypes were retained internally and not made available to the public, though some were used for ongoing development testing within Commodore before the company's collapse; a few leaked during the liquidation. Planned peripherals, including a 1 RAM expansion board designed to plug into a dedicated rear slot for enhanced memory in VIC mode, were abandoned and never reached production. This abrupt end to the C65 initiative hastened the erosion of Commodore's 8-bit product line, leaving the Commodore 64 without a direct upgrade amid shifting market demands and exacerbating financial strains that led to the firm's declaration in 1994. Meanwhile, preliminary rumors and leaked specifications—detailing features like C64 compatibility, 4096-color graphics, and a built-in 3.5-inch drive—began appearing in enthusiast magazines such as by mid-1991, fueling speculation among developers and users despite no official confirmation.

Legacy

Surviving prototypes

Approximately 205 Commodore 65 prototypes were produced, primarily featuring the Revision 2B motherboard, though estimates of surviving units range from 50 to around 200, including complete systems and partial boards; the highest known serial number is 000205, though most are non-functional due to missing or incomplete custom chips like the CSG 4567 GPU and issues such as excessive heat generation and absent RF video output. During Commodore's 1994 , these prototypes entered the market through sales by liquidators including the Grapevine Group and Software Hut, fetching prices between $95 and $149 each; in contrast, subsequent auctions of well-preserved examples have commanded sums exceeding $20,000, with one functional unit selling for nearly $39,000 in 2024. Notable surviving prototypes include serial number 000008, owned by collector Elliott and equipped with RAM expansion and custom EPROMs, as well as units in the collection of Moise Sunda featuring peripheral and testing cards; several have been displayed at events like the World of Commodore expo, where enthusiast Jim Brain showcased two examples in 2019, highlighting their rarity among private and community holdings. The technical state of these prototypes is limited by the absence of finalized —such as the incomplete Basic 10 implementation causing runtime errors—and reliance on early like the 910111 ROM in Revision 2B boards, restricting full operation; efforts have involved dumping and analyzing existing ROMs to enable partial functionality, including C64 compatibility modes that run about 75-80% of legacy software. As tangible artifacts of 's ambitious yet unrealized evolution of the 8-bit platform, surviving Commodore 65 prototypes serve as enduring symbols of alternate computing histories, often dubbed the "Holy Grail" among retro enthusiasts for embodying the "what if" of a C64 successor that could have bridged eras.

Modern recreations and emulations

The MEGA65 project, initiated in 2015 by Paul Gardner-Stephen in collaboration with the Museum of Electronic Games and Art, represents a modern FPGA-based recreation of the Commodore 65's design, aiming to realize the unreleased computer's potential through and software. The system achieves approximately 40 times the processing speed of the Commodore 64 while maintaining high compatibility with Commodore 65 software, including emulation of the VIC-IV video chip via FPGA implementation. It features 384 of fast accessible to the VIC-IV (with 128 occupied by ROM), 8 MB of HyperRAM for extended memory, and 32 of color RAM, supporting advanced graphics modes originally envisioned for the C65. Key hardware enhancements in the MEGA65 include a built-in 3.5-inch floppy drive for authentic media handling, Ethernet connectivity for network and remote program loading, and dual slots for rapid storage access at speeds up to 3000 /second. The project is fully open-source, with schematics, , and core designs available for community modification and replication. Production units began shipping in May 2022 following pre-orders opened in 2021, with over 800 systems shipped by 2023 and additional batches produced thereafter as of April 2025. Beyond hardware recreations, software emulations have enabled testing of Commodore 65 prototypes using custom dumps extracted from surviving units. Dedicated emulators like Hi65 provide high-level simulation of the C65 environment, executing 10 instructions directly and supporting prototype s for development and preservation efforts, though they lack full cycle-accurate replication. The MEGA65 has fostered a vibrant community, enabling demos of unreleased Commodore 65 software such as the C65 Photo Demo, which showcases the system's 256-color graphics capabilities. New games and applications, including titles like First Shot and collections in the MEGA65 Intro Disk series, have been developed specifically for the platform, blending retro aesthetics with modern enhancements. As of 2025, the project continues to evolve with production units now in stock, ongoing HyperRAM expansions to increase beyond the standard 8 MB, and updates like core version 0.97 in testing. In 2025, the project was showcased at Vintage Computer Festival West in August and Vintage Computer Festival Midwest in September, with talks and booths demonstrating advancements. Community events, including a dedicated talk at Vintage Computer Festival West in August 2025 and a booth at Vintage Computer Festival Midwest, have highlighted these advancements and demonstrated new software releases.

References

  1. [1]
    Commodore 65 Computer - Zimmers.net
    Statistics, features, and C65 resources: ; CPU: CSG 4510 ; Video: CSG 4569 "VIC-III" ; Sound: CSG 8580 "SID" (2X) ; Ports: CSG 4510 ; Keyboard: Full-sized 77 key ...
  2. [2]
    Commodore C65 Microcomputer - PhilReichert.org
    Feb 26, 2023 · The Commodore C65 was a prototype 8-bit microcomputer that was developed by Commodore Computers in the late 1980s.
  3. [3]
    A history of the Amiga, part 6: stopping the bleeding - Ars Technica
    Feb 10, 2008 · A history of the Amiga, part 6: stopping the bleeding. Ars continues ... Commodore had lost over $300 million between September 1985 and ...
  4. [4]
    A history of the Amiga, part 10: The downfall of Commodore
    Jan 22, 2017 · In 1993, sales fell by 20 percent, and Commodore lost $366 million. In the first quarter of 1994, the company announced a loss of $8.2 million.
  5. [5]
    Commodore 65 - the story of a computer that was never born
    1987 thus saw the birth of the idea of the Commodore 65. The computer was to incorporate the possibility of a Commodore 64 emulated mode, but mainly it was to ...Missing: specifications | Show results with:specifications
  6. [6]
    Commodore C65 System Engineering Design - PhilReichert.org
    Feb 26, 2023 · This system engineering overview describes the prototype Commodore C65 system that was being prepared for production in 1991.
  7. [7]
    Commodore 65 - Binary Dinosaurs
    The C65 project was started to try and capitalise on 10 years' worth of C64 software and programming skills whilst giving C64 owners something to upgrade to.
  8. [8]
    The Commodore 64DX/Commodore 65 - OSnews
    Feb 16, 2015 · In 1989, Commodore began an endeavor which was way overdue. The creation of a near Amiga-quality computer that is 8-bit in spirit, ...
  9. [9]
    SD Times Blog: Get your hands on the Commodore 65
    Feb 9, 2015 · The Commodore 65, you see, was a prototype. It was whipped up in 1990, and included many features designed to improve upon the 64.
  10. [10]
    c65 manual - Zimmers.net
    ... Revision 0.2 (pilot release) January 31, 1991 At this time, Pilot Production, the C65 system consists of either revision 2A or 2B PCB, 4510R3, 4567R5 (PAL ...
  11. [11]
    This Extremely Rare Commodore 65 Prototype is Selling For Nearly ...
    Apr 21, 2022 · There are an estimated 50 to 2,000 Commodore 65 machines still in existence, and only a handful of those are operational. The C65, originally ...
  12. [12]
    Secret Weapons of Commodore: The Commodore 65 - Floodgap
    C64DX, C64DX Development System (not the DX-64) Introduced Never officially. Prototypes escaped development hell when Commodore was liquidated in 1994.Missing: inception 1987-1988
  13. [13]
    Welcome to the MEGA65 - Dan Sanderson
    Jun 12, 2022 · Miraculously, we still have the Commodore original source code. The MEGA65 ROM fixes bugs and implements incomplete features of the actual C65 ...<|separator|>
  14. [14]
    The CSG 4510 Microcontroller Chip - C65 System Hardware
    Mar 1, 1991 · The CSG 4510 is a single chip 8-bit microcontroller with a 6502 microprocessor, timers, clocks, UART, memory map, shift registers, and 30 I/O ...
  15. [15]
    https://philreichert.org/commodore-c65/c65-to-c64-limitations.html
  16. [16]
    Commodore 65: Exploring Potential C64 Compatibility Challenges
    Jun 27, 2023 · The C65 featured a custom CSG 4510 R3 CPU, a MOS 6502 derivative, operating at a clock frequency of 3.54 MHz​​. This was over three times faster ...
  17. [17]
    https://philreichert.org/commodore-c65/system-memory-map.html
  18. [18]
    Secrets of the Commodore C65 System Memory Map
    Compared to other Commodore computers, the C65's memory map is unique. It features a larger address space of 24 bits, allowing for a maximum of 16MB of memory.
  19. [19]
    MEGA65 evolution - Part 2 - Fighting Computers
    Feb 1, 2024 · CBM added a Memory Management Unit (MMU) Co-processor specifically to manage these features. This concept was carried over to the C65, and ...
  20. [20]
    [PDF] 6581 sound interface device (sid) - Stanford CCRMA
    Dec 25, 1980 · The 6581 SID is a single-chip, 3-voice synthesizer/sound effects generator with 3 tone oscillators, 3 envelope generators, and 3 amplitude ...
  21. [21]
    Commodore 65 REAL Information!; Technical Specs
    Technical Specifications ; CPU, CSG 4510 (Modified MOS Technologies 65CE02) ; Speed, 3.54 Megahertz ; RAM, 128 Kilobytes (expandable to 8 megabytes) ; ROM, 128 ...Missing: processor | Show results with:processor
  22. [22]
    Commodore 8580 SID - Visual 6502
    The Commodore 8580 SID is a later version of the MOS 6581 Sound Interface Device (SID). It has a mixed analog and digital design.
  23. [23]
    C65 - C64-Wiki
    Jan 19, 2022 · The Commodore 65 (a.k.a.: C65), also known as the C64DX, is a prototype 8-bit computer by Commodore Business Machines. Contents. 1 History; 2 ...
  24. [24]
    Secret Weapons of Commodore: The Commodore 65
    ### Commodore 65 Compatibility Modes with C64 Summary
  25. [25]
    Commodore 65: Explaining the C65 and C64 operating modes
    Jul 2, 2023 · The C65 featured a custom CSG 4510 R3 CPU, operating at a clock frequency of 3.54 MHz—over three times faster than the C64's 1 MHz CPU. This ...
  26. [26]
    Commodore C65 Prototyp
    ### Commodore 65 C64 Compatibility Summary
  27. [27]
    MEGA65: The First Ten Years | Dan Sanderson
    Apr 15, 2025 · In this special edition of the Digest, we'll review the first ten years of the MEGA65 project through published media, articles, videos, and conference talks.Missing: primary | Show results with:primary
  28. [28]
    Zzap! Editorials 1991
    Will Commodore see TIB as sufficiently bolstering the C64 that no new machine is required. So what about the impact on the C65? 'I honestly don't know, but when ...
  29. [29]
    In 1990, Commodore turned the C64 into a console. This is the story ...
    Engineer Fred Bowen made some ROM revisions, including a new display screen that appeared if the GS was turned on without a cartridge. Without a keyboard, a ...<|separator|>
  30. [30]
    The Story of Commodore - Floodgap
    With investor support quickly eroding after the lawsuit, MOS rapidly found itself in financial trouble. ... Finally, in 1991, 64'er was permitted to view the new ...
  31. [31]
    COMPANY NEWS; COMMODORE INTERNATIONAL GOING OUT ...
    Apr 30, 1994 · The company last month reported a loss of $8.2 million, on sales of $70.1 million, for the quarter that ended on Dec. 31. In the comparable ...
  32. [32]
    An actual working Commodore 65 prototype is being auctioned off ...
    Apr 20, 2022 · In 1994 when Commodore International was liquidated, anywhere from 50 to 2,000 C65 prototypes reportedly found their way onto the open market.Missing: count surviving revision
  33. [33]
    Commodore 65: A 16-bit C-64 that never was
    Apr 5, 2018 · The mail-order dealer Grapevine Group sold a few hundred units at prices ranging from $95 to $149. Once they realized the machines had some ...
  34. [34]
    Rare Commodore C65 Prototype Sells for Nearly $39,000 on eBay
    Apr 5, 2024 · ... number 71, this unit has captivated enthusiasts and collectors ... With only a scant few prototypes ever produced, the Commodore 65 has ...
  35. [35]
    World of Commodore '19 | C64 OS
    Jan 15, 2020 · A Commodore C65 Prototype Two Commodore C65 Prototypes. Saving the best for last, Jim Brain brought not one but TWO Commodore C65 prototypes.
  36. [36]
    https://files.mega65.org/files/m/mega65-chipset-reference_4hh2eE.pdf
  37. [37]
    MEGA65 - 8-Bit Computer
    Complete 8-bit computer running around 40x faster than a C64 while being highly compatible. C65 design, mechanical keyboard, HD output, dual SD cards support.Filehost · MEGA≡65 User's Guide · M65Connect for Windows (Intel) · ROM FAQMissing: recreation | Show results with:recreation
  38. [38]
    [PDF] mega65-chipset-reference_4hh2eE.pdf
    Apr 3, 2024 · ... Commodore 65 prototypes that are known to exist either do not behave as specified, the specification lacks detail and the implementation is ...
  39. [39]
    Article Detail
    Technical specification ; GPU. VIC IV (backwards compatible to VIC-III and VIC-II); 128KB graphics memory. Palette of 2^23 colors (23 Bits: 7 red, 8 green, 8 ...
  40. [40]
    [PDF] mega65-userguide_53Cgq1.pdf
    Mar 4, 2024 · disk on the SD card or in the physical 3.5” floppy drive when the computer is switched on. When set to SDCARD disk image, the MEGA65 uses the ...
  41. [41]
    MEGA65 - highly advanced C64 and C65 compatible 8-bit computer
    In stock... RAM, 8 MB serial RAM, 64 MB SDRAM; VIC-IV video controller with VGA™ and digital video connectors; Digital and analog video output usable at the same time; 3.5 ...
  42. [42]
    MEGA65 - C64-Wiki
    Aug 27, 2023 · RAM: 384KB RAM visible to VIC-IV, 32KB colour RAM visible to VIC-IV. 8MB of Hyper RAM (aka Attic RAM). Media: D81 disk images from SD card ...Missing: color | Show results with:color
  43. [43]
    Support for Commodore C65 emulation - VICE - SourceForge
    Dec 28, 2008 · I am wondering whether it is possible for ViCE to support the Commodore 65 as an emulated platform. I have heard that the MESS-emulator supports ...
  44. [44]
    Hi65: a high-level Commodore 65 emulator
    Instead, configuring it to any mode (windowed or full screen) with hi65cfg.exe and then running hi65.exe will run it correctly in whatever mode you select.
  45. [45]
    Hi65, my high-level Commodore 65 emulator - Lemon64
    Aug 30, 2013 · I have created a Commodore 65 emulator. The emulator is called Hi65 and uses an HLE approach to execute BASIC 10 instructions directly.C65 Emulation on Vice - Commodore 64Looking for a Commodore 65 emulator for WindowsMore results from www.lemon64.com
  46. [46]
    Linux - MEGA65 Filehost
    C65 Photo Demo. Download file. 198. -. Demo. Demo. MEGA65, C65. c65pdemo.d81.zip. 000000674407-674 KB. Snoopy. 2021/01/22. c65pdemo;zip;C65 Photo Demo;Demo;Demo.Missing: unreleased | Show results with:unreleased
  47. [47]
    I demo First Shot! An exciting video game for the MEGA65 coming in ...
    Jan 30, 2023 · I'm super excited to share a new game for the @MEGA65retro from RetroCogs, First Shot! I also share a Christmas gift from my mother, ...Missing: C65 software
  48. [48]
    MEGA65 Intro Disk V4 - The Oasis BBS
    Apr 16, 2025 · This release offers new demos, updated tools, and first looks at games still in development. Everything runs on both MEGA65 hardware and the ...Missing: unreleased | Show results with:unreleased<|separator|>
  49. [49]
    VCF West: The MEGA65: Who Remembers the Commodore 65?
    Aug 29, 2025 · talk, MEGA65 contributor Dan Sanderson introduces the project and its connections with Commodore history ... VCF East: The Most Important Computer ...Missing: specifications | Show results with:specifications
  50. [50]
    MEGA65 at VCFMW 2025 - Reddit
    Sep 13, 2025 · Quick look at the MEGA65 booth by Steven https://retrocombs.com/mega65 together there with Dan https://dansanderson.com/mega65…