AMD AMD5K86 - Control Register 4 (CR4) Extensions

AMD~
AMD5J<!36 Processor Technical Reference Manual
18524BjO-Marl996
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
31
- Reserved
Global Page Extension
Machine Check Enable
Page Size Extension
Debugging 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.
876543210
---1111
Time Stamp Disable
Protected Virtual Interrupts
Virtual-8086 Mode Extensions
GPE
MCE
PSE
DE
TSD
PVI
VME
7
6
4
3
2
1
o
FIGURE 3-1. Control Register 4 (CR4)
3-2
Software Environment and Extensions