Intel Webcam 253668-032US User Manual

11-44   Vol. 3

MEMORY CACHE CONTROL

Example 11-5.  Get4KMemType() Pseudocode

IF IA32_MTRRCAP.FIX AND MTRRdefType.FE /* fixed registers enabled */

THEN IF PHY_ADDRESS is within a fixed range

return IA32_MTRR_FIX.Type;

FI;
FOR each variable-range MTRR in IA32_MTRRCAP.VCNT

IF IA32_MTRR_PHYSMASK.V = 0

THEN continue;

FI;
IF (PHY_ADDRESS AND IA32_MTRR_PHYSMASK.Mask) =

(IA32_MTRR_PHYSBASE.Base 
AND IA32_MTRR_PHYSMASK.Mask)

THEN

return IA32_MTRR_PHYSBASE.Type;

FI;

ROF;
return MTRRdefType.Type;

11.11.7.2   MemTypeSet() Function

The MemTypeSet() function in Example 11-6 sets a MTRR for the physical memory 
range specified by the parameters base and size to the type specified by type. The 
base address and size are multiples of 4 KBytes and the size is not 0.

Example 11-6.  MemTypeSet Pseudocode

IF CPU_FEATURES.MTRR (* processor supports MTRRs *)

THEN

IF BASE and SIZE are not 4-KByte aligned or size is 0

THEN return INVALID; 

FI;

IF (BASE + SIZE) wrap 4-GByte address space

THEN return INVALID; 

FI;

IF TYPE is invalid for Pentium 4, Intel Xeon, and P6 family

 

processors

THEN return UNSUPPORTED; 

FI;

IF TYPE is WC and not supported

THEN return UNSUPPORTED; 

FI;

IF IA32_MTRRCAP.FIX is set AND range can be mapped using a

fixed-range MTRR