How is the cpu clock connected to other components - clock

Question

How is the cpu clock connected to other components. and what do people mean by saying all operations start at a clock tick.

Answer 1

The CPU Clock drives the CPU. Internally there is a bus system, basically a bundle of electrical connections. Someone, and only one, may put their data on it. For example a register output, or the ALU result (Well, they don't want to, they're told to do so by the control unit, which makes sure only one entity may access the bus in write mode).
This operation is unsafe as logic may fluctuate the electrical signal several times while it moves through the logic gates until it stabilizes, or some signals will come earlier than others. This depends on capacitive and inductive effects and such, delaying the signals.
Because of this, no one will read the data off the bus until the clock triggers. The clock pulse indicates that enough time has passed that the signals ought to be safe and it is assumed the signal on the bus is stable.
This is done by simply using an and-gate or an edge detector with the clock signal on the devices that want to read from the bus.
Example:
Data-Bus ----/8----- [ ]
Data-In ----------- [ R ]
Data-Out ----------- [ E ]
Clk ----------- [ G ]
' Data-Out may be asyncronous like this, though not recommended, or on falling/low clock pulse, or the Data-Out signal is clock synced:
Data-Bus[0] = Data-Out AND Data[0]
Data-Bus[1] = Data-Out AND Data[1]
Data-Bus[2] = Data-Out AND Data[2]
[...]
' Data-In will almost always be clock synced
If (Data-In AND Raising-Clk-Edge)
{
Data[0] = Data-Bus[0]
Data[1] = Data-Bus[1]
[...]
}
This is of course highly dependant on your actual hardware. For example Read-Enable, Write-Enable and Output-Enable can be active low, etc.
There is a great youtube series of a guy actually building a CPU on a breadboard. While of course this is overly simplified in regards what a modern cpu does, it helps to understand the basics.
The cpu clock itself is usually not directly connected to other hardware, and instead the cpu generates the trigger pulses that tell others it's safe to read/write from/to the bus now.
Each instruction may be made up from several microinstructions. For example:
LDA #5, Load 5 into the A-Register
' Fetch
Put IP on Address bus, Enable memory out => Opcode for LDA-Immediate is now on Data-Bus
Write-Enable Instruction Register, Increment IP
' Decode with combinatorial logic
' CU realizes it needs another word from memory (the value) and it needs to go to the A-Register
' Execute
Put IP on Address bus, Enable memory out => #5 now on data-bus
Increment IP, Write-Enable A-Register => #5 now in A-Register
' Done
This is done by the cpu clock. the system clock has little to do with that.