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ATI R700 Technology
ATI R700-Family Instruction Set Architecture 4-1
Copyright © 2009 Advanced Micro Devices, Inc. All rights reserved.
Chapter 4
ALU Clauses
Software initiates an ALU clause with one of the CF_INST_ALU* control-flow
instructions, all of which use the CF_ALU_DWORD[0,1] microcode formats.
Instructions within an ALU clause, called ALU instructions, perform operations
using the scalar ALU.[X,Y,Z,W] and ALU.Trans units, which are described in this
chapter.
4.1 ALU Microcode Formats
ALU instructions are implemented with ALU microcode formats that are
organized in pairs of two 32-bit doublewords. The doubleword layouts in memory
are shown in Figure 4.1.
+0 and +4 indicate the relative byte offset of the doublewords in memory.
{OP2, OP3} indicates a choice between the strings OP2 and OP3 (which
specify two or three source operands).
LSB indicates the least-significant (low-order) byte.
Figure 4.1 ALU Microcode Format Pair
4.2 Overview of ALU Features
An ALU vector is 128 bits wide and consists of four 32-bit elements. The data
elements need not be related. The elements are organized in GPRs in little-
endian order, as shown in Figure 4.2. Element ALU.X is the least-significant (low-
order) element; element ALU.W is the most-significant (high-order) element.
Figure 4.2 Organization of ALU Vector Elements in GPRs
31 24 23 16 15 8 7 0
ALU_DWORD1_{OP2, OP3} +4
ALU_DWORD0 +0
<------------ LSB ------------>
127 96 95 64 63 32 31 0
ALU.W ALU.Z ALU.Y ALU.X
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