
AMD-K5 Processor
59
21062E/0—June 1997
AMD K86 Family BIOS and Software Tools Developers Guide
Preliminary Information
Table 19. Control Register 4 (CR4) Fields
Bit
Mnemonic
Description
Function
7
GPE
Global Page
Extension*
Enables retention of designated entries in the 4-Kbyte TLB or
4-Mbyte TLB during invalidations.
1 = enabled, 0 = disabled.
See
“Global Pages” on page 65 for details.
Enables machine-check exceptions.
1 = enabled, 0 = disabled.
See “Machine-Check Exceptions” on page 60 for details.
Enables 4-Mbyte pages.
1 = enabled, 0 = disabled.
See “4-Mbyte Pages” on page 60 for details.
Enables I/O breakpoints in the DR7–DR0 registers.
1 = enabled, 0 = disabled.
See “Debug Registers” on page 38 for details.
Selects privileged (CPL=0) or non-privileged (CPL>0) use of
the RDTSC instruction, which reads the Time Stamp Counter
(TSC).
1 = CPL must be 0, 0 =any CPL.
See “Time Stamp Counter (TSC)” on page 81 for details.
Enables hardware support for interrupt virtualization in
Protected mode.
1 = enabled, 0 = disabled.
See “Protected Virtual Interrupt (PVI) Extensions” on page 79
for details.
Enables hardware support for interrupt virtualization in
Virtual-8086 mode.
1 = enabled, 0 = disabled.
See “Virtual-8086 Mode Extensions (VME)” on page 67 for
details.
6
MCE
Machine-Check Enable
4
PSE
Page Size
Extension
3
DE
Debugging
Extensions
2
TSD
Time Stamp
Disable
1
PVI
Protected Virtual
Interrupts
0
VME
Virtual-8086
Mode Extensions
Note:
*
The AMD-K5 processor supports global paging only on Models 1, 2, and 3, with a Stepping of 4 or greater.