Natalie ShermanBusiness reporter
Real-mode programs freely execute CLI and STI to control interrupts, PUSHF and POPF to manipulate flags, INT n for DOS and BIOS calls, and IN/OUT for hardware I/O. In normal protected mode, these instructions are privilege-checked -- they execute normally if the caller has sufficient privilege, and fault otherwise. The 386 can't simply let V86 tasks execute them freely -- a DOS program disabling interrupts would bring down the whole system -- but trapping on every INT 21h call would make V86 impractically slow.
。同城约会对此有专业解读
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.
00:14, 28 февраля 2026Культура