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originally provided for remote job entry, the conceptual ancestor of IBM's later
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The Test PLA extends this idea further. It operates asynchronously with respect to the sequencer. After a protection test fires, the PLA needs time to evaluate and produce its redirect address. Instead of stalling, the 386 allows the next three micro-instructions to execute before the redirect takes effect -- and the microcode is carefully written to use these delay slots productively. This is tremendously confusing when reading the microcode for the first time (huge credit to the disassembly work by reenigne). But Intel did it for performance.