3-2
Software Environment and Extensions
AMD-K5 Processor Technical Reference Manual
18524C/0—Nov1996
The sections that follow provide details on the architectural
extensions visible to system and application software. Some
sections include pseudo-code algorithms for suggested BIOS
modifications to support the extensions. Architectural exten-
sions visible to debug and test software, such as I/O break-
points, are described in Chapter 7.
3.1
Control Register 4 (CR4) Extensions
Control register 4 contains bits that enable or specify many of
the extensions to the 486 architecture. The majority of the bits
in CR4 are reserved. The default state for all bits in CR4 is all
zeros. Figure 3-1 shows the format of CR4. Table 3-1 describes
the fields in CR4.
Figure 3-1. Control Register 4 (CR4)
Global Page Extension
GPE
7
Machine Check Enable
MCE
6
Page Size Extension
PSE
4
Debugging Extensions
DE
3
Time Stamp Disable
TSD
2
Protected Virtual Interrupts
PVI
1
Virtual-8086 Mode Extensions
VME
0
7
6
5
4
3
2
1
0
31
P
S
E
T
S
D
M
C
E
V
M
E
D
E
P
V
I
G
P
E
Reserved
8
Summary of Contents for AMD-K5
Page 1: ...AMD K5 Processor Technical Reference Manual TM...
Page 10: ...x AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 24: ...1 4 Overview AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 54: ...2 30 Internal Architecture AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 116: ...4 26 Performance AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 356: ...6 44 System Design AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 380: ...7 24 Test and Debug AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 396: ...A 16 AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...
Page 406: ...I 10 Index AMD K5 Processor Technical Reference Manual 18524C 0 Nov1996...