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From: jgd@cix.co.uk (John Dallman)
Newsgroups: comp.arch
Subject: Re: Computer architects leaving Intel...
Date: Fri, 30 Aug 2024 09:05 +0100 (BST)
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In article <vaqgtl$3526$1@dont-email.me>, cr88192@gmail.com (BGB) wrote:

> On 8/29/2024 11:23 AM, MitchAlsup1 wrote:

> > With differing instructions, how does a software vendor write 
> > software such that it can run near optimally on any implementation?
> 
> They presumably target whatever is common, or the least common 
> denominator (such as RV64G or RV64GC), and settle with "probably 
> good enough"...

ISVs can be proactive or passive about adopting a new ISA. Anyone
promoting a new ISA wants to motivate them to be proactive, but faces
problems with prerequisites: 

* Who can work with simulators, and who needs hardware? 
* Different kinds of software need more or less powerful hardware.
* Application people need an OS and development tools at minimum.
* Quite often they need other software: math libraries, databases, etc. 

> But, probably not too much different from other ISAs, just with a 
> lot more parties involved.

Variant ISAs create fear, uncertainty and doubt, and that means delay.
ISA promotors fear delay, because their investors will run out of
patience. 

> The alternative is that one expects that all the software be 
> rebuilt for the specific configuration being used, 

ISVs /really/ don't like that. It multiplies their testing and QA and
those are expensive. It rarely shows up problems, but convincing
themselves to do without it is hard for them. 

> or recompiled from source or some other distribution format on 
> the local machine which it is to be run (with binaries distributed 
> as some form of "portable IR").

ISVs get sceptical about that, because it's generating code they have not
tested. 

John