3-26 Software Environment and Extensions
AMD-K5 Processor Technical Reference Manual 18524C/0—Nov1996
3.2.2 Machine-Check Type Register (MCTR)
The processor latches the cycle definition and other informa-
tion about the current bus cycle in its 64-bit Machine-Check
Type Register (MCTR) at the same times that the Machine-
Check Address Register (MCAR) latches the cycle address:
when a bus-cycle error occurs. These errors are indicated
either by (a) system logic asserting BUSCHK, or (b) the proces-
sor asserting PCHK while system logic asserts PEN.
The MCTR can be read with the RDMSR instruction when the
ECX register contains the value 01h. Figure 3-9 and Table 3-7
show the formats of the MCTR register. The contents of the
register can be read with the RDMSR instruction. The proces-
sor clears the CHK bit (bit 0) in MCTR when the register is
read with the RDMSR instruction.
If system software has set the MCE bit in CR4 before the bus-
cycle error, the processor also generates a machine-check
exception as described in Section 3.1.1 on page 3-4.
Figure 3-9. Machine-Check Type Register (MCTR)
Locked Cycle LOCK 4
Memory or I/O Cycle M/IO 3
Data or Code Cycle D/C 2
Write or Read Cycle W/R 1
Valid Machine-Check Data CHK 0
54321063
C
H
K
D
/
C
W
/
R
L
O
C
K
M
/
I
O
Reserved
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