Filter
Top Products
icread
Instruction Cache Read
PPC440x5 CPU Core User’s Manual Preliminary
Page 318 of 589
instrset.fm.
September 12, 2002
Registers Altered
• ICDBDR
• ICDBTRH
• ICDBTRL
Invalid Instruction Forms
• Reserved fields
Programming Note
Execution of this instruction is privileged.
The PPC440x5 does not automatically synchronize context between an icread instruction and the subse-
quent mfspr instructions which read the results of the icread instruction into GPRs. In order to guarantee that
the mfspr instructions obtain the results of the icread instruction, a sequence such as the following must be
used:
icread regA,regB # read cache information (the contents of GPR A and GPR B are
# added and the result used to specify a cache line index to be read)
isync # ensure icread completes before attempting to read results
mficdbdr regC # move instruction information into GPR C
mficdbtrh regD # move high portion of tag into GPR D
mficdbtrl regE # move low portion of tag into GPR E
Architecture Note
This instruction is implementation-specific and programs which use this instruction may not be portable to
other PowerPC Book-E implementations. See Instruction Set Portability on page 250.