diff --git a/src/machine.adoc b/src/machine.adoc index c9412578e..261f3f41e 100644 --- a/src/machine.adoc +++ b/src/machine.adoc @@ -192,10 +192,17 @@ supervisor modes respectively. The "X" bit will be set if there are any non-standard extensions. -When "B" bit is 1, the implementation supports the instructions provided by the -Zba, Zbb, and Zbs extensions. When "B" bit is 0, it indicates that the +When the "B" bit is 1, the implementation supports the instructions provided by the +Zba, Zbb, and Zbs extensions. When the "B" bit is 0, it indicates that the implementation may not support one or more of the Zba, Zbb, or Zbs extensions. +When the "M" bit is 1, the implementation supports all multiply and +division instructions defined by the M extension. When the "M" bit +is 0, it indicates that the implementation may not support those +instructions. However if the Zmmul extension is suppported then +the multiply instructions it specifies are supported irrespective +of the value of the "M" bit. + [NOTE] ==== The `misa` CSR exposes a rudimentary catalog of CPU features to