# Is there any differce on cpu control register during switch between rv32 and rv64 isa？

**URL:** <https://forums.sifive.com/t/is-there-any-differce-on-cpu-control-register-during-switch-between-rv32-and-rv64-isa/2007>\
**Category:** General\
**Created:** [January 25, 2019, 7:24am UTC](https://forums.sifive.com/t/is-there-any-differce-on-cpu-control-register-during-switch-between-rv32-and-rv64-isa/2007 "2019-01-25T07:24:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![tugouxp](https://avatars.discourse-cdn.com/v4/letter/t/f07891/32.png) [@tugouxp](https://forums.sifive.com/u/tugouxp)\
**Post date:** [January 25, 2019, 7:24am UTC](https://forums.sifive.com/t/is-there-any-differce-on-cpu-control-register-during-switch-between-rv32-and-rv64-isa/2007/1 "2019-01-25T07:24:05Z")

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is there any differce on cpu control register during switch between rv32 and rv64 isa？

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**Author:** ![brucehoult](https://sea2.discourse-cdn.com/flex020/user_avatar/forums.sifive.com/brucehoult/32/24_2.png) [@brucehoult](https://forums.sifive.com/u/brucehoult)\
**Post date:** [January 25, 2019, 7:27am UTC](https://forums.sifive.com/t/is-there-any-differce-on-cpu-control-register-during-switch-between-rv32-and-rv64-isa/2007/2 "2019-01-25T07:27:16Z")

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SiFive cores can not switch between rv64 and rv32.