The silicon of the clock generator in the original 6502 looks completely different
from what we have in the 6509 and 8501.
Since the 6509 was manufactured in an older process technology than the 8501,
it's an interesting question if the first revision of the 6509 did "rocket testing"
for the clock generators of the later MOS CPUs.
When comparing the silicon of the 8501 and 6509 clock generator in one picture,
it appears that some of the parts in the chip layout look quite similar for both chips.
Attachment:
si_8501_6509_clock.png [ 254.89 KiB | Viewed 899 times ]
In the 6509, the clock generator circuitry is only dead weight:
Some vias are placed differently than in the 8501.
Quite some vias that connect to VCC are missing.
Outputs of all of the driver transistors are not connected to anything.
In the PHI2 driver, gate of the FETs (not) switching PHI2 to GND and gate of the FET (not) switching PHI2 to VCC are tied together.
Attachment:
8501_6509_clock_generator.png [ 90.21 KiB | Viewed 899 times ]
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