machine -> hart

src/machine.adoc

@@ -49,13 +49,13 @@ The `misa` CSR is MXLEN bits wide.
 The base width can be quickly ascertained using branches on the sign of
 the returned `misa` value, and possibly a shift left by one and a second
 branch on the sign. These checks can be written in assembly code without
-knowing the register width (MXLEN) of the machine. The base width is
+knowing the register width (MXLEN) of the hart. The base width is
 given by __MXLEN=2^MXL+4^__.
 
 The base width can also be found if `misa` is zero, by placing the
 immediate 4 in a register then shifting the register left by 31 bits at
-a time. If zero after one shift, then the machine is RV32. If zero after
-two shifts, then the machine is RV64, else RV128.
+a time. If zero after one shift, then the hart is RV32. If zero after
+two shifts, then the hart is RV64, else RV128.
 ====
 
 The Extensions field encodes the presence of the standard extensions,