Intel ARCHITECTURE IA-32 User Manual download pdf (Page 309)

100

101

Vol. 3A 7-41

MULTIPLE-PROCESSOR MANAGEMENT

6. Extract a sub ID given a full ID, maximum sub ID value and shift count.

// Returns the value of the sub ID, this is not a zero-based value

Unsigned char GetSubID(unsigned char Full_ID, unsigned char MaxSubIDvalue, unsigned

char Shift_Count)

{

MaskWidth = FindMaskWidth(MaxSubIDValue);

MaskBits = ((uchar) (0xff << Shift_Count)) ^ ((uchar) (0xff << Shift_Count + MaskWidth)) ;

SubID = Full_ID & MaskBits;

Return SubID;

}

Software must not assume local APIC_ID values in an MP system are consecutive. Non-consec-

utive local APIC_IDs may be the result of hardware configurations or debug features imple-

mented in the BIOS or OS.

An identifier for each hierarchical level can be extracted from an 8-bit APIC_ID using the

support routines illustrated in Example 7-1. The appropriate bit mask and shift value to construct

the appropriate bit mask for each level must be determined dynamically at runtime.

7.10.4 Identifying Topological Relationships in a MP System

To detect the number of physical packages, processor cores, or other topological relationships

in a MP system, the following procedures are recommended:

• Extract the three-level identifiers from the APIC ID of each logical processor enabled by

system software. The sequence is as follows (See the pseudo code shown in Example 7-2

and support routines shown in Example 7-1):

• The extraction start from the right-most bit field, corresponding to SMT_ID, the

innermost hierarchy in a three-level topology (See Figure 7-6). For the right-most

bit field, the shift value of the working mask is zero. The width of the bit field is

determined dynamically using the maximum number of logical processor per core,

which can be derived from information provided from CPUID.

• To extract the next bit-field, the shift value of the working mask is determined

from the width of the bit mask of the previous step. The width of the bit field is

determined dynamically using the maximum number of cores per package.

• To extract the remaining bit-field, the shift value of the working mask is

determined from the maximum number of logical processor per package. So the

remaining bits in the APIC ID (excluding those bits already extracted in the two

previous steps) are extracted as the third identifier. This applies to a non-clustered

MP system, or if there is no need to distinguish between PACKAGE_ID and

CLUSTER_ID.

If there is need to distinguish between PACKAGE_ID and CLUSTER_ID,

PACKAGE_ID can be extracted using an algorithm similar to the extraction of

1 2 ... 304 305 306 307 308 309 310 311 312 313 314 ... 635 636

Comments to this Manuals

No comments

Intel ARCHITECTURE IA-32 User Manual Page 309

Comments to this Manuals

Related products and manuals for Processors Intel ARCHITECTURE IA-32