The Unabridged Pentium 4 IA32 Processor Genealogy

Chapter 48. Pentium^® 4 FSB Blocking

The Previous Chapter

This chapter described the FSB locking mechanism, the reason for its existence, and the instructions that invoke it. It included:

• The Shared Resource Concept.

• Testing the Availability of and Gaining Ownership of Shared Resources.

• A Race Condition Can Present a Problem.

• Guaranteeing the Atomicity of a Read/Modify/Write.

• Locking a Cache Line.

This Chapter

This chapter describes the mechanism that permits FSB agents to limit the number of transactions that can be injected into the FSB. It includes:

• Assert BNR# When One Entry Remains.

• BNR# Can Be Used by a Debug Tool.

• Who Monitors BNR#.

• BNR# is a Shared Signal.

• The Stalled/Throttled/Free Indicator.

• Initial Entry to the Stalled State.

• The Throttled State. ...