Patent
1997-10-09
1999-12-21
Lall, Parshotam S.
395591, G06F 900
Patent
active
060060301
ABSTRACT:
A microprocessor includes a programmable instruction trap that can be used to deimplement instructions that lead to erroneous results. Upon discovery of a logic design defect, a microprocessor manufacturer can distribute an updated exception handler and a patch for a boot sequence. Upon power up, the boot sequence programs instructions to be deimplemented into a trap list. Each received instruction (issued by an application program, for example) not matching any listed instruction is executed in due course. When it matches a listed deimplemented instruction, the received instruction is trapped: it is not executed but is stored in a dedicated register. An exception handler is called that can examine the trapped instruction and substitute a suitable routine. If the trapped instruction is conditionally deimplemented and the problematic conditions do not pertain, the exception handler can reissue the instruction after temporarily deactivating the trapping function. Once the exception handler is done, the interrupted application program can resume.
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Anderson Clifton L.
Coulter Kenneth R.
Lall Parshotam S.
VLSI Technology Inc.
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