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]# comprises request Packet A.

  2. All of the FSB agents use the falling-edge of the two Address Strobes to latch Packet A into their input receivers. At this point, processors on the FSB have all of the information necessary to determine whether or not it is a memory transaction (i.e., the memory address and the transaction type) and, if it is, they initiate a snoop in their internal caches. The snoop result will be delivered when the transaction has entered its Snoop Phase.

  3. In the second half of the BCLK cycle, the Request Agent:

    - drives out additional transaction information on A[35:3]#,

    - drives out additional transaction information on REQ[4:0]#,

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

  4. The information on A[35:3]# and REQ[4:0]# comprises request Packet B.

  5. All of the FSB agents use the rising-edge of the two Address Strobes to latch Packet B into their input receivers.

..................Content has been hidden....................

You can't read the all page of ebook, please click here login for view all page.
Reset
18.219.236.62