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The present x86 isn’t made from the ‘same process and materials’ as the 6502, any more than a modern automobile and a Model T are.

Your point is taken that they’re both based on silicon, just as cars are still mostly stamped sheet metal, even today. Nevertheless, decades of continuous process and materials development have steadily improved silicon performance. Yes, there were some explorations into other base materials for CPUs (notably gallium arsenide) but in the end silicon won the day.

We’ll get to your 6502 thought experiment in a moment. First, let’s discuss what’s changed since 1977-ish.

The biggest silicon improvement? Channel length (feature size generally) makes a huge difference in CPU performance. Contemporary CPUs have channel lengths about 1000x shorter than the 6502:

• 6502: 8um
• Typical CMOS today: 7nm

This key difference affects gate delays, which ultimately determine the achievable cycle time. Having smaller features also reduces capacitance and wire delays, further boosting speed.

Also note the 6502 was an NMOS part (CMOS ones came later) which also puts it at a disadvantage over contemporary CPUs. But really, it’s the smaller feature size that makes the difference.

Now, could the 6502 be run at GHz speeds in a modern process? Very likely, but it might require some tweaking, especially the introduction of some pipelines to break up delay paths.

And note that the 6502 I/O speed also limits its performance: some onboard memory would be needed to break that bottleneck. Modern CPUs have buffer memories and/or caches with fast, low-latency paths to the CPU.

To give you an idea of what’s possible, here’s a 6502 implemented in an FPGA, that runs at 100MHz: https://blog.adafruit.com/2021/10/13/the-100-mhz-6502-microprocessor-fpga-emulation-vintagecomputing/ One key detail: at startup, this device copies the entire 6502 address space to internal RAM, speeding things up considerably. Only I/O makes it out to the pins.

As it is, 100MHz on a Spartan-6 is pretty good for that FPGA, hinting that 6502 decoding and execution are pretty efficient. This would bode well for a custom ASIC hitting GHz speed.

The present x86 isn’t made from the ‘same process and materials’ as the 6502, any more than a modern automobile and a Model T are.

Your point is taken that they’re both based on silicon, just as cars are still mostly stamped sheet metal, even today. Nevertheless, decades of continuous process and materials development have steadily improved silicon performance. Yes, there were some explorations into other base materials for CPUs (notably gallium arsenide) but in the end silicon won the day.

We’ll get to your 6502 thought experiment in a moment. First, let’s discuss what’s changed since 1977-ish.

The biggest silicon improvement? Channel length (feature size generally) makes a huge difference in CPU performance. Contemporary CPUs have channel lengths about 1000x shorter than the 6502:

• 6502: 8um
• Typical CMOS today: 7nm

This key difference affects gate delays, which ultimately determine the achievable cycle time. Having smaller features also reduces capacitance and wire delays, further boosting speed.

Also note the 6502 was an NMOS part (CMOS ones came later) which also puts it at a disadvantage over contemporary CPUs. But really, it’s the smaller feature size that makes the difference.

Now, could the 6502 be run at GHz speeds in a modern process? Very likely, but it might require some tweaking, especially the introduction of some pipelines to break up delay paths.

And note that the 6502 I/O speed also limits its performance: some onboard memory would be needed to break that bottleneck. Modern CPUs have buffer memories and/or caches with fast, low-latency paths to the CPU.

To give you an idea of what’s possible, here’s a 6502 implemented in an FPGA, that runs at 100MHz: https://blog.adafruit.com/2021/10/13/the-100-mhz-6502-microprocessor-fpga-emulation-vintagecomputing/ One key detail: at startup, this device copies the entire 6502 address space to internal RAM, speeding things up considerably. Only I/O makes it out to the pins.

As it is, 100MHz on a Spartan-6 is pretty good for that FPGA, hinting that 6502 decoding and execution are pretty efficient. This would bode well for a custom 6502 ASIC hitting GHz speed.

The present x86 isn’t made from the ‘same process and materials’ as the 6502, any more than a modern automobile and a Model T are.

Your point is taken that they’re both based on silicon, just as cars are still mostly stamped sheet metal, even today. Nevertheless, decades of continuous process and materials development have steadily improved silicon performance. Yes, there were some explorations into other base materials for CPUs (notably gallium arsenide) but in the end silicon won the day.

We’ll get to your 6502 thought experiment in a moment. First, let’s discuss what’s changed since 1977-ish.

The biggest silicon improvement? Channel length (feature size generally) makes a huge difference in CPU performance. Contemporary CPUs have channel lengths about 1000x shorter than the 6502:

• 6502: 8um
• Typical CMOS today: 7nm

This key difference affects gate delays, which ultimately determine the achievable cycle time. Having smaller features also reduces capacitance and wire delays, further boosting speed.

Also note the 6502 was an NMOS part (CMOS ones came later) which also puts it at a disadvantage over contemporary CPUs. But really, it’s the smaller feature size that makes the difference.

Now, could the 6502 be run at GHz speeds in a modern process? Very likely, but it might require some tweaking, especially the introduction of some pipelines to break up delay paths.

And note that the 6502 I/O speed also limits its performance: some onboard memory would be needed to break that bottleneck. Modern CPUs have buffer memories and/or caches with fast, low-latency paths to the CPU.

To give you an idea of what’s possible, here’s a 6502 implemented in an FPGA, that runs at 100MHz: https://blog.adafruit.com/2021/10/13/the-100-mhz-6502-microprocessor-fpga-emulation-vintagecomputing/ One key detail: at startup, this device copies the entire 6502 address space to internal RAM, speeding things up considerably. Only I/O makes it out to the pins.

The present x86 isn’t made from the ‘same process and materials’ as the 6502, any more than a modern automobile and a Model T are.

Your point is taken that they’re both based on silicon, just as cars are still mostly stamped sheet metal, even today. Nevertheless, decades of continuous process and materials development have steadily improved silicon performance. Yes, there were some explorations into other base materials for CPUs (notably gallium arsenide) but in the end silicon won the day.

We’ll get to your 6502 thought experiment in a moment. First, let’s discuss what’s changed since 1977-ish.

The biggest silicon improvement? Channel length (feature size generally) makes a huge difference in CPU performance. Contemporary CPUs have channel lengths about 1000x shorter than the 6502:

• 6502: 8um
• Typical CMOS today: 7nm

This key difference affects gate delays, which ultimately determine the achievable cycle time. Having smaller features also reduces capacitance and wire delays, further boosting speed.

Also note the 6502 was an NMOS part (CMOS ones came later) which also puts it at a disadvantage over contemporary CPUs. But really, it’s the smaller feature size that makes the difference.

Now, could the 6502 be run at GHz speeds in a modern process? Very likely, but it might require some tweaking, especially the introduction of some pipelines to break up delay paths.

And note that the 6502 I/O speed also limits its performance: some onboard memory would be needed to break that bottleneck. Modern CPUs have buffer memories and/or caches with fast, low-latency paths to the CPU.

To give you an idea of what’s possible, here’s a 6502 implemented in an FPGA, that runs at 100MHz: https://blog.adafruit.com/2021/10/13/the-100-mhz-6502-microprocessor-fpga-emulation-vintagecomputing/ One key detail: at startup, this device copies the entire 6502 address space to internal RAM, speeding things up considerably. Only I/O makes it out to the pins.

As it is, 100MHz on a Spartan-6 is pretty good for that FPGA, hinting that 6502 decoding and execution are pretty efficient. This would bode well for a custom ASIC hitting GHz speed.

The present x86 isn’t made from the ‘same process and materials’ as the 6502, any more than a modern automobile and a Model T are.

Your point is taken that they’re both based on silicon, just as cars are still mostly stamped sheet metal, even today. Nevertheless, decades of continuous process and materials development have steadily improved silicon performance. Yes, there were some explorations into other base materials for CPUs (notably gallium arsenide) but in the end silicon won the day.

We’ll get to your 6502 thought experiment in a moment. First, let’s discuss what’s changed since 1977-ish.

The biggest silicon improvement? Channel length (feature size generally) makes a huge difference in CPU performance. Contemporary CPUs have channel lengths about 1000x shorter than the 6502:

• 6502: 8um
• Typical CMOS today: 7nm

This key difference affects gate delays, which ultimately determine the achievable cycle time. Having smaller features also reduces capacitance and wire delays, further boosting speed.

Also note the 6502 was an NMOS part (CMOS ones came later) which also puts it at a disadvantage over contemporary CPUs. But really, it’s the smaller feature size that makes the difference.

Now, could the 6502 be run at GHz speeds in a modern process? Very likely, but it might require some tweaking, especially the introduction of some pipelines to break up delay paths.

And note that the 6502 I/O speed also limits its performance: some onboard memory would be needed to break that bottleneck. Modern CPUs have buffer memories and/or caches with fast, low-latency paths to the CPU.

To give you an idea of what’s possible, here’s a 6502 implemented in an FPGA, that runs at 100MHz: https://blog.adafruit.com/2021/10/13/the-100-mhz-6502-microprocessor-fpga-emulation-vintagecomputing/ One key detail: this device copies the entire 6502 address space to internal RAM, speeding things up considerably.

The present x86 isn’t made from the ‘same process and materials’ as the 6502, any more than a modern automobile and a Model T are.

Your point is taken that they’re both based on silicon, just as cars are still mostly stamped sheet metal, even today. Nevertheless, decades of continuous process and materials development have steadily improved silicon performance. Yes, there were some explorations into other base materials for CPUs (notably gallium arsenide) but in the end silicon won the day.

We’ll get to your 6502 thought experiment in a moment. First, let’s discuss what’s changed since 1977-ish.

The biggest silicon improvement? Channel length (feature size generally) makes a huge difference in CPU performance. Contemporary CPUs have channel lengths about 1000x shorter than the 6502:

• 6502: 8um
• Typical CMOS today: 7nm

This key difference affects gate delays, which ultimately determine the achievable cycle time. Having smaller features also reduces capacitance and wire delays, further boosting speed.

Also note the 6502 was an NMOS part (CMOS ones came later) which also puts it at a disadvantage over contemporary CPUs. But really, it’s the smaller feature size that makes the difference.

Now, could the 6502 be run at GHz speeds in a modern process? Very likely, but it might require some tweaking, especially the introduction of some pipelines to break up delay paths.

And note that the 6502 I/O speed also limits its performance: some onboard memory would be needed to break that bottleneck. Modern CPUs have buffer memories and/or caches with fast, low-latency paths to the CPU.

To give you an idea of what’s possible, here’s a 6502 implemented in an FPGA, that runs at 100MHz: https://blog.adafruit.com/2021/10/13/the-100-mhz-6502-microprocessor-fpga-emulation-vintagecomputing/ One key detail: at startup, this device copies the entire 6502 address space to internal RAM, speeding things up considerably. Only I/O makes it out to the pins.