The TRS-80 Model 100: Modding for Increased Speed and Performance

The TRS-80 Model 100, released in 1983, was a revolutionary portable device with low power usage. While its 80C85 CPU had the potential to run at 5 MHz, it operated at just under 2.5 MHz due to a 1:2 divider on the input clock. However, enthusiasts have found a way to boost its speed through modding.

Ken, in a recent video featuring his ‘daily driver’ M100, showcased a ready-made solution from the Bitchin100 website. This mod utilizes a new board design and the M100 ROM image, as increasing the CPU clock on old CPUs is not a simple task. Upgrading the CPU clock also requires components on the CPU bus to operate at higher speeds, posing technical challenges.

To overcome these obstacles, Ken’s mod board was designed to piggyback on top of the MPU package. Additionally, the system ROM chip, originally at 600 ns, needed replacement with a faster one like the Atmel AT27C256R (45 ns). This necessitated an additional carrier board to handle pinout incompatibilities.

The mod board also addresses access speed issues with the system RAM. By bypassing certain power-saving logic and triggering the power-up signal earlier (A*), the original base system RAM can still function adequately.

However, the UART, responsible for clocking, cannot handle a 5 MHz signal. To resolve this, the mod board includes a 2.45 MHz output pad.

Once the mod is fully installed and the Model 100 is closed up again, the system demonstrates increased speed and performance. However, it is worth noting that some games, such as Starblaze 100, may no longer function correctly. Nevertheless, users can switch between 2.5 and 5 MHz modes via the command line, mitigating this drawback.

The modification has been well-received by TRS-80 Model 100 enthusiasts, thanks to the efforts of Stephen Walters, who shared the tip with the community. With this mod, the beloved Model 100 can now offer improved speed and capabilities to its users, further extending its lifespan in the ever-evolving world of technology.

TRS-80 Model 100 Mod FAQ

1. What is the TRS-80 Model 100?
The TRS-80 Model 100 is a portable device that was released in 1983. It featured a low power usage design and used an 80C85 CPU.

2. What is the purpose of the mod mentioned in the article?
The mod mentioned in the article is designed to boost the speed of the TRS-80 Model 100. It utilizes a new board design and replaces the system ROM chip to achieve increased performance.

3. What challenges are involved in upgrading the CPU clock?
Upgrading the CPU clock on old CPUs like the one in the TRS-80 Model 100 poses technical challenges. It requires ensuring that components on the CPU bus can operate at higher speeds.

4. How does the mod board overcome these challenges?
The mod board piggybacks on top of the MPU package to overcome the challenges of upgrading the CPU clock. It also requires replacing the system ROM chip with a faster one and addresses access speed issues with the system RAM.

5. Can the mod affect the functionality of certain games?
Yes, once the mod is installed, some games such as Starblaze 100 may no longer function correctly. However, users can switch between 2.5 and 5 MHz modes to mitigate this issue via the command line.

6. Who developed and shared this mod with the TRS-80 Model 100 community?
Stephen Walters developed and shared this mod tip with the TRS-80 Model 100 community. His efforts have been well-received by enthusiasts of the device.