The Bus and Processor Clocks
The BSEL Outputs
Each model of Pentium® 4 processor is designed to operate at a certain internal clock frequency as well as a FSB frequency. A clock generator on the system board generates the Bus Clock (BCLK) to the processor(s) and all other FSB agents. The processor provides two outputs, BSEL[1:0], that are connected to the system board's clock generator and the 2-bit pattern that is output on these two signals tells the clock generator the frequency of the BCLK to be supplied to all FSB agents. Table 43-1 on page 1117 defines the possible settings on the processor's BSEL[1:0] outputs. Currently, the Pentium® 4's FSB has a BCLK speed of 200MHz.
| BSEL1 | BSEL0 | BCLK Frequency Required |
|---|---|---|
| 0 | 0 | 100MHz. ... |
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