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The MOS 6502 Processor
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The 6502 is an 8-bit processor designed by MOS Technology in 1975, based on the design of the Motorola 6800. When it was introduced it was the least expensive full featured CPU on the market by far, at about 1/6th the price, or less, of competing designs from larger companies such as Motorola and Intel. It was nevertheless faster than most of them, and, along with the Zilog Z80, sparked off a series of computer projects that would eventually result in the home computer revolution of the 1980s. The 6502 design was originally second-sourced by Rockwell and Synertek and later licensed to a number of companies; it is still made for embedded systems.
Unlike the Intel 8080 and its kind, the 6502 had very few registers. It was an 8-bit processor with 16-bit address bus. Inside was one 8-bit data register (accumulator), two 8-bit index registers and an 8-bit stack pointer. When the 6502 was introduced, RAM was actually faster than CPUs, so it made sense to optimize for RAM access rather than increase the number of registers on a chip.
6502 processors were used in a variety of home computers of the early 80s, for example in:
References:
Documentation archive at 6502.org
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The MOS 7501 Processor
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| The 7501 variant of the 6510 was used in Commodore's C16, C116 and Plus/4 home computers, and the 2 MHz-capable 8502 variant was used in the Commodore C128. All these CPUs are opcode compatible (including undocumented opcodes). |
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The MOS 8500 Processor
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In 1985 MOS produced the 8500, an HMOS version of the 6510. Other than the process change, it is virtually identical to the NMOS version of the 6510. The 8500 was originally designed for use in the modernised C64, the C64C. However in 1985, limited quantities of 8500s were found on older NMOS based C64s. It finally made its official debut in 1987, appearing in a motherboard using the new 85xx HMOS chipset.
The MOS 8502 was also based on the MOS 6510 that was used in the Commodore 64. The 8502 added the ability to run at a double (2.048 MHz) clock rate, in addition to the standard 1.024 MHz rate used by the Commodore 64. The pinout is a little bit different from the 6510. The 8502 has an extra I/O-pin and lacks the PHI2-pin that the 6510 had.
The 7501/8501 variant of the 6510 was used in Commodore's C16, C116 and Plus/4 home computers, and the 2 MHz-capable 8502 variant was used in the Commodore C128. All these CPUs are opcode compatible (including undocumented opcodes). |
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MOS 650x peripheral 6526 |
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| Core Frequency: | 1 MHz | | Board Frequency: | 1 MHz |
| Data bus (ext.): | 8 Bit | | Address bus: | 8 Bit | | Voltage: | 5 V | | Manufactured: | week 29/1983 | | Package Type: | Ceramic
DIP-40
Silvercap
Goldpins |
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MOS 650x peripheral 6529B |
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| Core Frequency: | 1 MHz | | Board Frequency: | 1 MHz |
| Data bus (ext.): | 8 Bit | | Address bus: | 8 Bit | | Voltage: | 5 V | | Manufactured: | week 01/1984 | | Package Type: | Ceramic
DIP-20
Silvercap
Goldpins |
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