6502 vs. 65C816

Attribute	6502	65C816
Manufacturer	MOS Technology	WDC (Western Design Center)
Release Year	1975	1983
Architecture	8-bit	16-bit
Registers	3 general purpose registers (A, X, Y)	3 general purpose registers (A, X, Y), 16-bit accumulator
Addressable Memory	64 KB	16 MB
Instruction Set	56 instructions	over 100 instructions

Introduction

When it comes to vintage microprocessors, the 6502 and 65C816 are two popular choices that have been used in a variety of computers and gaming consoles. Both processors have their own unique attributes and capabilities that make them stand out in the world of retro computing. In this article, we will compare the features of the 6502 and 65C816 processors to help you understand the differences between these two iconic chips.

Architecture

The 6502 processor is an 8-bit microprocessor that was first introduced by MOS Technology in 1975. It has a simple and efficient architecture with a 16-bit address bus and an 8-bit data bus. The 6502 has three general-purpose registers (A, X, and Y) and supports a variety of addressing modes for efficient memory access. In contrast, the 65C816 is a 16-bit microprocessor that is an enhanced version of the 6502. It has a 24-bit address bus and a 16-bit data bus, allowing for larger memory addressing and more data processing capabilities.

Instruction Set

The 6502 processor has a relatively small instruction set with only 56 instructions, which makes it easy to learn and program for. It uses a simple and efficient design that allows for fast execution of instructions. The 65C816, on the other hand, has a more complex instruction set with over 150 instructions, including new 16-bit instructions for enhanced performance. This expanded instruction set gives the 65C816 more flexibility and power in handling complex tasks compared to the 6502.

Memory Management

One of the key differences between the 6502 and 65C816 processors is their memory management capabilities. The 6502 processor is limited to a 64KB address space, which can be a constraint when working with larger programs or data sets. In contrast, the 65C816 has a 16MB address space, allowing for more extensive memory addressing and larger program sizes. This makes the 65C816 a more suitable choice for applications that require a larger memory capacity.

Compatibility

Both the 6502 and 65C816 processors are backward compatible with the 6502 instruction set, which means that programs written for the 6502 can run on the 65C816 without modification. This compatibility makes it easy to upgrade systems from the 6502 to the 65C816 without having to rewrite existing software. However, the 65C816 also introduces new instructions and features that are not available in the 6502, which can provide additional performance benefits for applications that take advantage of these enhancements.

Performance

When it comes to performance, the 65C816 has a clear advantage over the 6502 due to its 16-bit architecture and expanded instruction set. The 65C816 can execute more complex instructions and handle larger data sets more efficiently than the 6502. This makes the 65C816 a better choice for applications that require higher performance and more advanced features. However, the 6502 is still a capable processor for simpler tasks and retro computing projects that do not require the advanced capabilities of the 65C816.

Conclusion

In conclusion, the 6502 and 65C816 processors are both iconic chips with their own unique attributes and capabilities. The 6502 is a simple and efficient 8-bit processor that is easy to program for and suitable for a wide range of retro computing projects. On the other hand, the 65C816 is a more powerful 16-bit processor with enhanced features and performance benefits that make it a better choice for more demanding applications. Whether you choose the 6502 or 65C816 will depend on your specific needs and the complexity of the tasks you need to perform.