Vol. 3C 36-55

INTEL® PROCESSOR TRACE

36.4.2.18   PSBEND Packet

Dependencies

TriggerEn

Generation 

Scenario

Periodic, based on the number of output bytes generated while tracing. PSB is sent 

when IA32_RTIT_STATUS.PacketByteCnt=0, and each time it crosses the software 

selected threshold after that. May be sent for other micro-architectural conditions 

as well.

Description

PSB is a unique pattern in the packet output log, and hence serves as a sync point for the decoder. It is a pattern 

that the decoder can search for in order to get aligned on packet boundaries. This packet is periodic, based on the 

number of output bytes, as indicated by IA32_RTIT_STATUS.PacketByteCnt. The period is chosen by software, via 

IA32_RTIT_CTL.PSBFreq (see Section 36.2.7.2). Note, however, that the PSB period is not precise, it simply reflects 

the average number of output bytes that should pass between PSBs. The processor will make a best effort to 

insert PSB as quickly after the selected threshold is reached as possible. The processor also may send extra

PSB packets for some micro-architectural conditions.

PSB also serves as the leading packet for a set of “status-only” packets collectively known as PSB+ (Section 36.3.7). 

Application

When a PSB is seen, the decoder should interpret all following packets as “status only”, until either a PSBEND or 

OVF packet is encountered. “Status only” implies that the binding and ordering rules to which these packets nor-

mally adhere are ignored, and the state they carry can instead be applied to the IP payload in the FUP packet that is 

included.

Table 36-37. PSBEND Packet Definition

Name

PSBEND Packet

Packet Format

Dependencies

TriggerEn

Generation 

Scenario

Always follows PSB packet, separated by PSB+ packets

Description

PSBEND is simply a terminator for the series of “status only” (PSB+) packets that follow PSB (Section 36.3.7).

Application

When a PSBEND packet is seen, the decoder should cease to treat packets as “status only”.

Table 36-36. PSB Packet Definition (Contd.)

7

6

5

4

3

2

1

0

0

0

0

0

0

0

0

1

0

1

0

0

1

0

0

0

1

1