Dual 867MHz Is now Dual 800MHz After Motherboard Replacement?

Question

so i replaced the motherboard on my dual 867MHz G4.
the computer turns on now, and i did a fresh 10.4.11 install...but i noticed that it says "Dual 800" instead of "Dual 867" in my "About This Mac" now. i typed "sysctl hw.cpufrequency" in the terminal and discovered that it is actually running at 800MHz, and not 867MHz.
so why did i lose 67MHz with a new motherboard? it was the correct motherboard...any ideas?

Answer 1

G4 MDD Processor and bus speeds
There are two classes of Processors for the Mirrored Drive Doors G4 Macs, and they do not follow the main distinction between the products -- Firewire 400 Vs. Firewire 800.
In the Mirrored Drive Doors models, processor speed is determined by a combination of the jumpers on the processor modules and the Bus Speed of the system into which the processor is installed.
• Install a processor intended for a faster Bus speed into a system with a slower Bus speed, and it will be clocked slower and run slower than expected. 133/167 slower.
• Install a processor intended for a slower bus speed into a system with a faster Bus speed, and it will be clocked faster -- in most cases so fast that it will immediately crash.
133 MHz Bus speed:
867 MHz dual w 1 MB cache (each processor) from Fw 400 model
1.0 GHz single w 1 MB cache from Fw 800 model
167 MHz Bus speed:
1.0 GHz dual w 1 MB cache (each processor) from Fw 400 model
1.25 GHz dual w 2 MB cache (each processor) from Fw 400 model
1.25 GHz dual w 1 MB cache (each processor) from Fw 800 model
1.42 GHz dual w 2 MB cache (each processor) from Fw 800 model
1.25 GHz single w 1 MB cache from "education only" 2003 model
-compiled from the Power Mac G4 (Mirror/FW800) Service Manual, General Information section.