Commodore Amiga A500 vs A500+ Differences Explained

The Commodore Amiga A500 and A500+ are iconic 16-bit computers, but subtle hardware changes distinguish them. This article outlines the key technical specifications, chipset upgrades, memory configurations, and compatibility nuances between the original A500 and the revised A500+ model released in 1991.

Release History and Context

The original Amiga 500 was launched in 1987 and became the best-selling Amiga model. It utilized the Original Chip Set (OCS) and defined the home computer gaming landscape of the late 1980s. In 1991, Commodore released the A500+ as a cost-reduced and slightly enhanced revision intended to extend the lifecycle of the platform before the arrival of the Amiga 1200.

Chipset and Graphics

One of the primary differences lies in the chipset. The original A500 uses the OCS, while the A500+ features the Enhanced Chip Set (ECS). The ECS allowed for higher resolutions in interlaced modes and supported a larger range of colors in specific display modes. While most software remained compatible, the ECS chipset provided a marginal improvement in graphical flexibility for newer titles designed to take advantage of the hardware revision.

Memory Configuration

Memory architecture saw a significant change between the two models. The standard A500 came with 512 KB of Chip RAM and often included an additional 512 KB of Slow RAM via a trapdoor expansion. In contrast, the A500+ came standard with 1 MB of Chip RAM. This unified memory pool allowed for more complex graphics and larger game levels without requiring immediate hardware expansion, though it removed the separate Slow RAM bank found in the original configuration.

Kickstart ROM Version

Perhaps the most impactful difference for users was the operating system version. The original A500 typically shipped with Kickstart 1.2 or 1.3. The A500+ shipped with Kickstart 2.0 built into the motherboard. While Kickstart 2.0 offered improved system commands and better hard drive support, it introduced compatibility issues with some older games that relied on specific memory maps or direct hardware access typical of Kickstart 1.3.

Physical Design Changes

Externally, the machines are nearly identical, but keen observers can spot differences. The A500+ case plastic was often a slightly lighter shade of grey compared to the original. The keyboard feel was updated, and the power LED was moved from the side of the case to the front right corner above the keyboard. Additionally, the A500+ removed the internal reset button found on some early A500 revisions, relying solely on the keyboard combination for resets.

Compatibility Considerations

Due to the Kickstart 2.0 ROM and the ECS chipset, the A500+ is not 100% compatible with the entire A500 software library. Some early demos and games that utilized specific timing or memory tricks failed to run on the newer model. Enthusiasts often recommend the original A500 for pure retro gaming compatibility, while the A500+ is valued for its increased standard memory and ability to run later titles more efficiently without immediate upgrades.

Conclusion

Choosing between the A500 and A500+ depends on specific user needs. The A500+ offers a more robust standard configuration with 1 MB of Chip RAM and a newer operating system, making it better suited for productivity and later games. However, the original A500 remains the gold standard for maximum software compatibility across the entire Amiga library. Both models remain cherished pieces of computing history that defined a generation of home computing.