The Debug Store (DS) Mechanism
If enabled, the Debug Store mechanism permits the processor to automatically store branch (Branch Trace Store, or BTS) and PEBS records in a memory buffer referred to as the DS save area.
The DS mechanism is available in Real Mode.
The programmer can determine if a processor supports the DS feature by executing a CPUID request type 1 and verifying that EDX =1. Assuming that the bit is set to one, the programmer must also check the following two bits: