Vol. 3B 17-21

DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES

The IA32_DS_AREA MSR holds the 64-bit linear address of the first byte of the DS buffer management area. The 
structure of a branch trace record is similar to that shown in Figure 17-6, but each field is 8 bytes in length. This 
makes each BTS record 24 bytes (see Figure 17-9). The structure of a PEBS record is similar to that shown in 
Figure 17-7, but each field is 8 bytes in length and architectural states include register R8 through R15. This makes 
the size of a PEBS record in 64-bit mode 144 bytes (see Figure 17-10).

Figure 17-8.  IA-32e Mode DS Save Area

Figure 17-9.  64-bit Branch Trace Record Format

BTS Buffer Base

BTS Index

BTS Absolute 

BTS Interrupt 

PEBS Absolute

PEBS Interrupt

PEBS 

Maximum

Maximum

Threshold

PEBS Index

PEBS Buffer Base

Threshold

Counter Reset

Reserved

0H

8H

10H

18H

20H

28H

30H

38H

40H

48H

50H

Branch Record 0

Branch Record 1

Branch Record n

PEBS Record 0

PEBS Record 1

PEBS Record n

BTS Buffer

PEBS Buffer

DS Buffer Management Area

IA32_DS_AREA MSR

Last Branch From

Last Branch To

Branch Predicted

0H

8H

10H

0

63

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