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Date:      Sun, 2 Jun 2024 20:01:18 +0100
From:      Jessica Clarke <jrtc27@freebsd.org>
To:        Robert Clausecker <fuz@freebsd.org>
Cc:        tuexen@freebsd.org, freebsd-riscv <freebsd-riscv@freebsd.org>, Mitchell Horne <mhorne@freebsd.org>, strajabot@gmail.com
Subject:   Re: Detecting the Zbb extension on riscv64
Message-ID:  <C3248C99-0EE1-4AD2-B83A-71444D909584@freebsd.org>
In-Reply-To: <Zly7E7MFMIuVqj02@fuz.su>
References:  <ZlxZn5IQuQ-zqbwl@fuz.su> <5343E09C-017B-40B7-9349-01F1195BBB7C@freebsd.org> <Zlx2u52Xw7Aw6svM@fuz.su> <232F8595-5C7A-4ABD-961D-4779CED5A5D6@freebsd.org> <Zly7E7MFMIuVqj02@fuz.su>

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On 2 Jun 2024, at 19:33, Robert Clausecker <fuz@freebsd.org> wrote:
>=20
> Hi Michael,
>=20
> Am Sun, Jun 02, 2024 at 06:37:44PM +0200 schrieb tuexen@freebsd.org:
>>> [U74 Core Complex Manual]: =
https://starfivetech.com/uploads/u74_core_complex_manual_21G1.pdf
>> Thanks for the pointer. Zbr is not mentioned there...
>=20
> It's not mentioned (though the next revision mentions Zba and Zbb), =
but
> the instructions of Zba and Zbb are listed as being available.

The U74 has evolved over many years with multiple versions. The
Unmatched has a version from late 2018 (its mimpid is 0x20181004 as
printed at boot) which predates Zb* ratification. You need to look at
the manual for the board in question[1], not StarFive=E2=80=99s manual
corresponding to their newer board and thus core revision.

Jess

[1] =
https://sifive.cdn.prismic.io/sifive/1a82e600-1f93-4f41-b2d8-86ed8b16acba_=
fu740-c000-manual-v1p6.pdf




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