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User’s Manual
IBM PowerPC 750GX and GL RISC Microprocessor
Exceptions
Page 174 of 377
gx_04.fm.(1.2)
March 27, 2006
Like the external interrupt, a system management interrupt is signaled to the 750GX by the assertion of an
input signal. The system management interrupt signal (SMI) is expected to remain asserted until the interrupt
is taken. If SMI is negated early, recognition of the interrupt request is not guaranteed. After the 750GX
begins execution of the system management interrupt handler, the system can safely negate SMI. After the
assertion of SMI is detected, the 750GX stops dispatching instructions and waits for all pending instructions
to complete. This allows any instructions in progress that need to take an exception to do so before the
system management interrupt is taken.
When a system management interrupt exception is taken, instruction fetching resumes at offset 0x01400
from the base address indicated by MSR[IP].
4.5.16 Thermal-Management Interrupt Exception (0x01700)
A thermal-management interrupt is generated when the junction temperature crosses a threshold
programmed in either THRM1 or THRM2. The exception is enabled by the thermal-management interrupt
enable (TIE) bit of either THRM1 or THRM2, and can be masked by setting MSR[EE].
Table 4-13 lists register settings when a thermal-management interrupt exception is taken.
Table 4-12. System Management Interrupt Exception—Register Settings
Register Setting Description
SRR0
Set to the effective address of the instruction that the processor would have attempted to execute next if no exception
conditions were present.
SRR1
0 Loaded with equivalent MSR bits.
1:4 Cleared.
5:9 Loaded with equivalent MSR bits.
10:15 Cleared.
16:31 Loaded with equivalent MSR bits.
MSR
POW 0
ILE —
EE 0
PR 0
FP 0
ME —
FE0 0
SE 0
BE 0
FE1 0
IP —
IR 0
DR 0
PM 0
RI 0
LE Set to value of ILE
Table 4-13. Thermal-Management Interrupt Exception—Register Settings
Register Setting Description
SRR0
Set to the effective address of the instruction that the processor would have attempted to execute next if no exception
conditions were present.
SRR1
0 Loaded with equivalent MSR bits
1:4 Cleared
5:9 Loaded with equivalent MSR bits
10:15 Cleared
16:31 Loaded with equivalent MSR bits
MSR
POW 0
ILE —
EE 0
PR 0
FP 0
ME —
FE0 0
SE 0
BE 0
FE1 0
IP —
IR 0
DR 0
PM 0
RI 0
LE Set to value of ILE