Intel ARCHITECTURE IA-32 User Manual

Optimizing Cache Usage 6
6-37
In scenario to the right, in Figure 6-7, keeping the data in one way of the
second-level cache does not improve cache locality. Therefore, use
prefetcht0 to prefetch the data. This amortizes the latency of the
memory references in passes 1 and 2, and keeps a copy of the data in
second-level cache, which reduces memory traffic and latencies for
passes 3 and 4. To further reduce the latency, it might be worth
considering extra
prefetchnta instructions prior to the memory
references in passes 3 and 4.
In Example 6-7, consider the data access patterns of a 3D geometry
engine first without strip-mining and then incorporating strip-mining.
Note that 4-wide SIMD instructions of Pentium III processor can
process 4 vertices per every iteration.
Example 6-7 Data Access of a 3D Geometry Engine without Strip-mining
while (nvtx < MAX_NUM_VTX) {
prefetchnta vertex
i
data // v =[x,y,z,nx,ny,nz,tu,tv]
prefetchnta vertex
i+1
data
prefetchnta vertex
i+2
data
prefetchnta vertex
i+3
data
TRANSFORMATION code // use only x,y,z,tu,tv of a vertex
nvtx+=4
}
while (nvtx < MAX_NUM_VTX) {
prefetchnta vertex
i
data // v =[x,y,z,nx,ny,nz,tu,tv]
// x,y,z fetched again
prefetchnta vertex
i+1
data
prefetchnta vertex
i+2
data
prefetchnta vertex
i+3
data
compute the light vectors // use only x,y,z
LOCAL LIGHTING code // use only nx,ny,nz
nvtx+=4
}

Intel ARCHITECTURE IA-32 Specifications

General

Instruction Set	x86
Instruction Set Type	CISC
Memory Segmentation	Supported
Operating Modes	Real mode, Protected mode, Virtual 8086 mode
Max Physical Address Size	36 bits (with PAE)
Max Virtual Address Size	32 bits
Architecture	IA-32 (Intel Architecture 32-bit)
Addressable Memory	4 GB (with Physical Address Extension up to 64 GB)
Floating Point Registers	8 x 80-bit
MMX Registers	8 x 64-bit
SSE Registers	8 x 128-bit
Registers	General-purpose registers (EAX, EBX, ECX, EDX, ESI, EDI, ESP, EBP), Segment registers (CS, DS, SS, ES, FS, GS), Instruction pointer (EIP), Flags register (EFLAGS)
Floating Point Unit	Yes (x87)