Thomas Christoph has built a reputation for recreating rare and sought-after Commodore accessories, and his latest project is no exception. His updated version of the TurboMaster, originally designed by Steve Schnedler in 1991, revives an accelerator that briefly boosted Commodore 64 performance before support for it vanished in 1992. The new TurboMaster V3 keeps the essence of the original while addressing its flaws, making it a far more reliable option for vintage computing enthusiasts.
This project was recently featured on the YouTube channel Reviving Retro, where a detailed look at the TurboMaster V3 was shared, along with its performance, history, and practical use. The video provides an in-depth demonstration of how this updated accelerator enhances the Commodore 64 experience.
A Look Back at the TurboMaster’s Origins
The TurboMaster was developed to speed up the Commodore 64 from 1 MHz to 4 MHz, a significant boost at the time. Schnedler’s version, however, wasn’t entirely original—it was itself a reverse-engineered clone of a German accelerator called the Turbo Process. The German board’s PAL chips had their security fuses left intact, allowing Schnedler to analyze and replicate its design.
The TurboMaster introduced some fixes over its predecessor. The most notable change was modifying the memory location that controlled acceleration. The original Turbo Process had a fatal flaw—many software programs would inadvertently disable the accelerator by writing to that memory location. Schnedler resolved this by implementing a workaround that ensured programs wouldn’t shut it off by mistake. He also improved the hardware by adding an aluminum case for better durability.
What’s New in TurboMaster V3?
Thomas Christoph’s update stays true to the original TurboMaster while incorporating thoughtful improvements. The new version still runs at 4 MHz using a 65C02 processor, but it includes modern fast SRAM, an updated ROM, and built-in JiffyDOS. It’s designed to work with the Commodore 64 and can be used with the 128 in 64-mode.
The TurboMaster V3 comes with four switches:
- Enable/Disable: Turns acceleration on or off.
- ROM 1/ROM 2: Switches between internal and external ROM options.
- Manual/Soft: Determines how the accelerator interacts with peripherals.
- 1 MHz/4 MHz: Sets the operating speed.
GEOS users will appreciate the flexibility this accelerator provides. Historically, GEOS wouldn’t boot at 4 MHz, requiring users to manually switch to 1 MHz first. The updated TurboMaster V3 retains this functionality, making it compatible with software that expects a standard-speed CPU.
Master Adapter: Expanding Capability
Schnedler’s project didn’t stop with the accelerator—he also developed the Master Adapter, allowing users to add either GEOS RAM or a RAM Expansion Unit (REU). Thomas Christoph has recreated this adapter as well, making it possible to use the TurboMaster alongside expanded memory configurations.
The adapter consists of two stacked circuit boards. The smaller one connects directly to the C64’s cartridge port and buffers the signals, while the larger board manages data exchange between the TurboMaster and the memory expansion. A set of switches lets users toggle between GEOS RAM and REU modes.
When the Master Adapter was first introduced, the necessary GEOS RAM drivers were already built into the system. However, using an REU required additional drivers, which were developed later by Paul Bosacki. His work made it possible to fully integrate the TurboMaster with CMD hardware, allowing users to get the most out of their expanded setups.
Performance and Practicality
For its time, the TurboMaster was an impressive speed boost, but it never reached the market penetration of the later SuperCPU, which pushed speeds past 20 MHz. The TurboMaster V3 sits between a stock Commodore 64 and the high-end SuperCPU, making it a practical upgrade for users who want better performance without the bulk and cost of the more advanced accelerator.
A quick speed test demonstrates the impact of the TurboMaster. A simple BASIC loop that normally takes around 22.5 seconds to execute runs in under 7 seconds when accelerated—roughly three times faster. For applications like GEOS, productivity software, and even certain games, this speed increase can make a noticeable difference.
Price and Availability
Back in 1991, the TurboMaster sold for $199, while the Master Adapter was originally $49 before increasing to $59. Adjusted for inflation, those numbers would be significantly higher today. While Christoph’s reproduction isn’t the cheapest accessory on the market, its value comes from the improved reliability and functionality that weren’t present in the original.
Final Thoughts
The TurboMaster V3 offers a blend of historical accuracy and modern refinement. It faithfully recreates an accelerator that disappeared too soon, while fixing its known shortcomings. Paired with the Master Adapter, it brings expanded memory support, making it a solid choice for Commodore 64 enthusiasts looking to upgrade their systems. Though it won’t replace the SuperCPU, it provides a practical speed boost without the complexity of a full-fledged accelerator.
For those interested, Christoph’s work can be found at COREi64, where he continues to produce high-quality reproductions of rare Commodore hardware.
