SYNCD X,$Y,$Z
Timing:
SYNCD: υ
Description:
Synchronize data cache und main memory in the region $Y+$Z to X+$Y+$Z.
| SYNCD: | "Synchronize data" When executed from nonnegative locations, these instructions have no effect on registers or memory if neither a write buffer nor a "write back" data cache are present. But when such a buffer or cache exists, they force the computer to make sure that all data for the X+1 bytes M[$Y+$Z] through M[$Y+$Z+X], or M[$Y+Z] through M[$Y + Z + X], will be present in memory. (Otherwise the result of a previous store instruction might appear only in the cache; the computer is being told that now is the time to write the information back, if it hasn't already been written. A program can use this feature before outputting directly from memory.) No protection failure occurs if the memory is not accessible. The action is similar when SYNCD is executed from a negative address, but in this case the specified bytes are also removed from the data cache (and from a secondary cache, if present). The operating system can use this feature when a page of virtual memory is being swapped out, or when data is input directly into memory. |