The Unabridged Pentium 4 IA32 Processor Genealogy

The Source Synchronous Strobes

The Request Agent starts driving a transaction request on the rising-edge of BCLK0. In Figure 49-1 on page 1205, a request is issued at the start of BCLK cycle 1 and another at the start of BCLK cycle 3. The signals that comprise the Request Phase signal group are divided into subgroups on the system board:

• The Address Strobe 0 signal trace is routed with the A[16:3]# and REQ[4:0]# signal traces.

• The Address Strobe 1 signal trace is routed with the A[35:17]# signal traces.

1. In the first half of the BCLK cycle, the Request Agent:

   - drives out address bits [35:3] on A[35:3]#,

   - drives out the transaction type on REQ[4:0]#,

   - drives both of the Address Strobe signals (ADSTB[1:0]#) low.

   The information on A[35:3]# and REQ[4:0]# ...