5-64
Bus Interface
AMD-K5 Processor Technical Reference Manual
18524C/0—Nov1996
5.2.22
FERR (Floating-Point Error)
Output
Summary
The processor asserts FERR to report the occurrence of an
unmasked floating-point exception resulting from the execu-
tion of a floating-point instruction. This signal is provided to
allow the system logic to handle this exception in a manner
consistent with IBM-compatible PC/AT systems.
The state of the numeric error (NE) bit in CR0 does not affect
the FERR signal.
Driven
The processor drives FERR every clock during memory cycles
(including cache writethroughs and writebacks), cache hits of
all types, I/O cycles, and locked cycles in the normal operating
modes (Real, Protected, and Virtual-8086) and in SMM. FERR
is not driven during the Shutdown, Halt, Stop Grant, or Stop
Clock states, or while RESET, INIT, or PRDY is asserted.
Details
The processor asserts FERR on the instruction boundary of the
next floating-point instruction or WAIT instruction that occurs
following the floating-point instruction that caused the
unmasked floating-point exception—that is, FERR is not
asserted at the time the exception occurs. The IGNNE signal
does not affect the assertion of FERR.
FERR is negated during the following conditions:
■
Following the successful execution of the floating-point
instructions FCLEX, FINIT, FSAVE, and FSTENV
■
Under certain circumstances, following the successful exe-
cution of the floating-point instructions FLDCW, FLDENV,
and FRSTOR, which load the floating-point status word or
the floating-point control word
■
Following the rising transition of RESET
FERR is always driven except in Tri-State Test mode.
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...