Control Register 4 (CR4) Extensions
3-15
18524C/0—Nov1996
AMD-K5 Processor Technical Reference Manual
Figure 3-6. EFLAGS Register
Table 3-4. Virtual-Interrupt Additions to EFLAGS Register
Bit
Mnemonic
Description
Function
20
VIP
Virtual Interrupt Pend-
ing
Set by the operating system (via the EFLAGS image on the stack)
when an external maskable interrupt (INTR) occurs for a Virtual-
8086 program who’s VIF bit is cleared. The bit is checked by the
processor when the program subsequently attempts to set VIF.
19
VIF
Virtual Interrupt Flag
When the VME bit in CR4 is set, the VIF bit is modified by the
processor when a Virtual-8086 program running at less privilege
than the IOPL attempts to modify the IF bit. The VIF bit is used by
the operating system to determine whether a maskable interrupt
should be passed on to the program or held pending.
ID Flag
ID
21
Virtual Interrupt Pending
VIP
20
Virtual Interrupt Flag
VIF
19
Alignment Check
AC
18
Virtual-8086 Mode
VM
17
Resume Flag
RF
16
Nested Task
NT
14
I/O Privilege Level
IOPL
13–12
Overflow Flag
OF
11
Direction Flag
DF
10
Interrupt Flag
IF
9
Trap Flag
TF
8
Sign Flag
SF
7
Zero Flag
ZF
6
Auxiliary Flag
AF
4
Parity Flag
PF
2
Carry Flag
CF
0
9
8
7
6
5
4
3
2
1
0
10
11
12
13
14
15
16
17
18
19
20
21
I
O
P
L
31 30 29 28 27 26 25 24 23 22
A
F
P
F
Z
F
S
F
I
F
D
F
T
F
O
F
N
T
R
F
V
M
A
C
V
I
F
V
I
P
I
D
C
F
Reserved
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...