142
Fetch and Decode Pipeline Stages
AMD Athlon™ Processor x86 Code Optimization
22007E/0—November 1999
Figure 5. Fetch/Scan/Align/Decode Pipeline Hardware
The most common x86 instructions flow through the DirectPath
pipeline stages and are decoded by hardware. The less common
instructions, which require microcode assistance, flow through
the VectorPath. Although the DirectPath decodes the common
x86 instructions, it also contains VectorPath instruction data,
which allows it to maintain dispatch order at the end of cycle 5.
Figure 6. Fetch/Scan/Align/Decode Pipeline Stages
1
2
3
4
5
6
E n try
P o in t
D e c o d e
I-C A C H E
Q u a d w o rd
Q u e u e
F E T C H
S C A N A L IG N 1 /
M E C T L
A L IG N 2 /
M E R O M
E D E C /
M E D E C
M R O M
3
M a c ro O p s
D e c o d e
D e c o d e
D e c o d e
D e c o d e
D e c o d e
D e c o d e
D e c o d e
D e c o d e
D e c o d e
1 6 b y te s
D ire c tP a th
D ire c tP a th
V e c to rP a th
V e c to rP a th
ID E C
F E T C H
S C A N
A L IG N 1
A L IG N 2
E D E C
1
2
3
M E C T L
M E R O M
M E S E Q
D ir e c tP a th
V e c to rP a th
4
5
ID E C
6
Summary of Contents for Athlon Processor x86
Page 1: ...AMD Athlon Processor x86 Code Optimization Guide TM...
Page 12: ...xii List of Figures AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 16: ...xvi Revision History AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 202: ...186 Page Attribute Table PAT AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 252: ...236 VectorPath Instructions AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...
Page 256: ...240 Index AMD Athlon Processor x86 Code Optimization 22007E 0 November 1999...