From e77c75b01ff9a4fbfd94a1a1f089ae59ff288223 Mon Sep 17 00:00:00 2001 From: Luke Kenneth Casson Leighton Date: Tue, 31 Mar 2020 11:53:02 +0100 Subject: [PATCH] whitespace --- openpower/isans_letter.mdwn | 60 ++++++++++++++++++------------------- 1 file changed, 30 insertions(+), 30 deletions(-) diff --git a/openpower/isans_letter.mdwn b/openpower/isans_letter.mdwn index 9f22f5690..300ac2e85 100644 --- a/openpower/isans_letter.mdwn +++ b/openpower/isans_letter.mdwn @@ -21,48 +21,48 @@ added is formalised and standardised, such that we (and others) have a clear, standards-non-disruptive, atomic and non-intrusive path to extend the POWER ISA. -## Overview +## Overview -The PowerPC Instruction Set Architecture (ISA) is an abstract model of a +The PowerPC Instruction Set Architecture (ISA) is an abstract model of a computer. This is what programmers use when they write programs for the machine, -even if indirectly via a compiler for a high level language. We must be -conservative in how we add to the ISA to: - -* not break existing programs +even if indirectly via a compiler for a high level language. We must be +conservative in how we add to the ISA to: + +* not break existing programs * be mindful as to how others may wish to add to the ISA in the future - -This document describes our strategy. - - -## ISA modes and escape sequences - -New chips usually need to be able to run older (legacy) software that is -incompatible with the latest and greatest ISA. Eg: 64 bit chip must be able to + +This document describes our strategy. + + +## ISA modes and escape sequences + +New chips usually need to be able to run older (legacy) software that is +incompatible with the latest and greatest ISA. Eg: 64 bit chip must be able to run older 16 bit and 32 bit software. - -To enable backwards compatability the CPU will be set into 'legacy' mode. This -is done with an ISA Mode switch, also known as ISA Muxing or ISA Namespaces. - -The operating system is able to quickly change between 'modern' ISA mode and -various legacy modes. - -Another technique is an ISA escape-sequence. This is a type of mode that is + +To enable backwards compatability the CPU will be set into 'legacy' mode. This +is done with an ISA Mode switch, also known as ISA Muxing or ISA Namespaces. + +The operating system is able to quickly change between 'modern' ISA mode and +various legacy modes. + +Another technique is an ISA escape-sequence. This is a type of mode that is only operational for a short time, unlike 32 or 64 bit which would be for the -entire run of a program. +entire run of a program. + - ## What are we adding to the ISA - -When high quality graphical display were developed the CPUs at the time were -shown to not be able to run the display fast enough. The solution was the use of + +When high quality graphical display were developed the CPUs at the time were +shown to not be able to run the display fast enough. The solution was the use of Graphics cards, these are specialised computers that are good at rendering pixels; often by doing the same thing in different parts of the screen at the same time (in parallel). These specialised computers are called Graphical -Processing Units (GPUs). - +Processing Units (GPUs). + The parallelism of some GPUs is thousands. This has led to GPUs being used to solve non graphical problems where high parallelism is useful. - + **break** # Letter regarding ISAMUX / NS -- 2.30.2