From: Luke Kenneth Casson Leighton Date: Thu, 26 Apr 2018 23:52:00 +0000 (+0100) Subject: clarify X-Git-Tag: convert-csv-opcode-to-binary~5452 X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=ad6830542628b57b46c07597148684f4eb400a3b;p=libreriscv.git clarify --- diff --git a/isa_conflict_resolution.mdwn b/isa_conflict_resolution.mdwn index 64b2147d5..f31e9026d 100644 --- a/isa_conflict_resolution.mdwn +++ b/isa_conflict_resolution.mdwn @@ -2,16 +2,32 @@ ## Executive Summary -A non-invasive backwards-compatible change to make -mvendorid and marchid being read-only to be a formal declaration of an -architecture having no Custom Extensions, and being permitted to be -WARL in order to support multiple simultaneous architectures on the -same processor (or hart) permits not only backwards and forwards -compatibility with existing implementations of the RISC-V Standard, -not only permits seamless transitions to future versions of the -RISC-V Standard (something that is not possible at the moment), but -permanently fixes the problem of clashes in Custom Extension opcodes -on a global basis. +A non-invasive backwards-compatible change to make mvendorid and marchid +being read-only to be a formal declaration of an architecture having no +Custom Extensions, and being permitted to be WARL in order to support +multiple simultaneous architectures on the same processor (or per hart +or harts) permits not only backwards and forwards compatibility with +existing implementations of the RISC-V Standard, not only permits seamless +transitions to future versions of the RISC-V Standard (something that is +not possible at the moment), but fixes the problem of clashes in Custom +Extension opcodes on a global worldwide permanent and ongoing basis. + +Summary of impact and benefits: + +* Implementation impact for existing implementations (even though + the Standard is not finalised) is zero. +* Impact for future implementations compliant with (only one) version of the + RISC-V Standard is zero. +* Benefits for implementations complying with (one or more) versions + of the RISC-V Standard is: increased customer acceptance due to + a smooth upgrade path at the customer's pace and initiative vis-a-vis + legacy proprietary software. +* Benefits for implementations deploying multiple Custom Extensions + are a massive reduction in NREs and the hugely reduced ongoing software + toolchain maintenance costs plus the benefit of having security updates + from upstream software sources due to + *globally unique identifying information* being in the toolchains + *even for Custom Extensions*. ## Introduction