From: Luke Kenneth Casson Leighton Date: Thu, 26 Mar 2020 12:24:01 +0000 (+0000) Subject: add para X-Git-Tag: convert-csv-opcode-to-binary~3060 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=461348e6069dd39194ddcd97097d60d01b2f1624;p=libreriscv.git add para --- diff --git a/openpower/isans_letter.mdwn b/openpower/isans_letter.mdwn index e203b57ca..22563a8e0 100644 --- a/openpower/isans_letter.mdwn +++ b/openpower/isans_letter.mdwn @@ -4,10 +4,15 @@ Hardware-level dynamic ISA Muxing (also known as ISA Namespaces and ISA escape-sequencing) is commonly used in instruction sets, in an arbitrary and ad-hoc fashion, added often on an on-demand basis. Examples include: -* Setting a SPR to switch the meaning of certain opcodes for Little-Endian -/ Big-Endian behaviour (present in POWER and SPARC) * Setting a SPR to -provide "backwards-compatibility" for features from older versions of -an ISA (such as changing to new ratified versions of the IEEE754 standard) +* Setting a SPR to switch the meaning of certain opcodes for Little-Endian / + Big-Endian behaviour (present in POWER and SPARC) +* Setting a SPR to provide "backwards-compatibility" for features from + older versions of an ISA (such as changing to new ratified versions of + the IEEE754 standard) + +(These we term "ISA Muxing" because, ultimately, they are extra bits +(or change existing bits) in the actual instruction decoder phase, +which involves "MUXes" to switch them on and off). The Libre-SOC team, developing a hybrid CPU-VPU-GPU, needs to add significantly and strategically to the POWER ISA to support, for example,