diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/counters.tex | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/src/counters.tex b/src/counters.tex index bd89ccb..7425a49 100644 --- a/src/counters.tex +++ b/src/counters.tex @@ -133,9 +133,7 @@ real-time clock, and, for realistic real-time clock frequencies, should never overflow in practice. The execution environment should provide a means of determining the period of a counter tick (seconds/tick). -The period must be constant. -The real-time clocks of all harts in a single user application -should be synchronized to within one tick of the real-time clock. +The period should be constant within a small error bound. The environment should provide a means to determine the accuracy of the clock (i.e., the maximum relative error between the nominal and actual real-time clock periods). @@ -144,8 +142,15 @@ clock periods). On some simple platforms, cycle count might represent a valid implementation of RDTIME, in which case RDTIME and RDCYCLE may return the same result. + +It is difficult to provide a strict mandate on clock period given the +wide variety of possible implementation platforms. The error bound +should be evaluated relative to the requirements of the platform. \end{commentary} +The real-time clocks of all harts in a single user application +should be synchronized to within one tick of the real-time clock. + The RDINSTRET pseudoinstruction reads the low XLEN bits of the {\tt instret} CSR, which counts the number of instructions retired by this hart from some arbitrary start point in the past. RDINSTRETH is |