6–12
Privileged Architecture Library Code
29 September 1997 – Subject To Change
21164PC Implementation of the Architecturally Reserved Opcodes
6.6.4 HW_MFPR and HW_MTPR Instructions
The HW_MFPR and HW_MTPR instructions are used to access internal state from
the IDU, MTU, and Dcache. The HW_MFPR from IDU IPRs has a latency of one
cycle (HW_MFPR in cycle n results in data available to the using instruction in
cycle n+1). HW_MFPR from MTU and Dcache IPRs has a latency of two cycles.
IDU hardware slots each type of MXPR to the correct IEU pipe (refer to
Table 5–1).
Figure 6–4 and Table 6–7 describe the format and fields of the HW_MFPR and
HW_MTPR instructions.
Figure 6–4 HW_MFPR and HW_MTPR Instruction Format
Table 6–7 HW_MFPR and HW_MTPR Format Description
Field
Value
Description
OPCODE
19
16
1D
16
The OPCODE field contains 19
16
for HW_MFPR.
The OPCODE field contains 1D
16
for HW_MTPR.
RA/RB
—
Must be the same; source register for HW_MTPR and destination
register for HW_MFPR.
Index
—
Specifies the IPR. Refer to Table 5–1 for field encoding. Refer to
Chapter 5 for more details about specific IPRs.
00
15
16
20
21
25
26
31
LJ-03472.AI4
Index
OPCODE
RA
RB