Timeline for Why are PDP-7-style microprogrammed instructions out of vogue?
Current License: CC BY-SA 4.0
3 events
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| Aug 27 at 15:21 | comment | added | supercat | ...otherwise be performed by an instruction and then clear itself once execution was complete. If an interrupt happens immediately after a "skip" instruction, the saved PC value would have bit 0 set, and on return from interrupt the "skip" instruction would be "executed", but without being allowed to actually do anything. | |
| Aug 27 at 15:19 | comment | added | supercat | Skipping an instruction on the PDP-11 would be complicated by the fact instructions which use program counter postincrement mode are treated as a one-word instruction that, during execution, bumps the program counter past a fetched operand word, and skipping the effects of the instruction entirely would cause the following word that would normally be treated as data to instead be executed as an instruction. Were it not for that, I would think than an instruction skip could be handled by having LSB of the program counter (not needed for accessing) suppress register updates etc. that would... | |
| Apr 18 at 17:00 | history | answered | Aron Insinga | CC BY-SA 4.0 |