Re: IBM's PPC being open sourced .. what does this mean for embedded devices ?

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.arch.embedded
Subject	Re: IBM's PPC being open sourced .. what does this mean for embedded devices ?
Date	2019-09-17 10:13 +0200
Organization	A noiseless patient Spider
Message-ID	<qlq4iq$e53$1@dont-email.me> (permalink)
References	<qlokni$qpk$1@dont-email.me>
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On 16/09/2019 20:36, kristoff wrote:
> HI all,
> 
> 
> I know is this kind-of old news by now, but -as far as I see- this has
> not been discussed here:
> 
> IBM is open-sourcing their PowerPC processor design.

No, they are not (as far as I understand the situation).  The linked
article seems a bit mixed up as to what they are giving away (they are
mixed up about RISC-V too).

When talking about processor licensing, there are many levels.  You can
license the ISA - the instructions, register setup, instruction codings,
etc.  This is the minimum you need in order to make a cpu that will run
binaries for that processor.  You can license design files (Verlig,
VHDL, etc.) for some or all of an implementation.  You can license hard
macros for some or all of an implementation.  You can license the right
to use names, trademarks, patents, etc.  You can license the right to
modify and expand on any of this.

As far as I know, IBM has offered commercial licenses on all of these
bits - just as ARM, MIPS, etc. do.  Some customers have taken the ISA
and made their own implementations, others have taken complete hard
macros and put them on ASICs, others go somewhere in between.

From this article, it seems IBM is giving free licensing for the ISA.
That means you can make your own processor in an FPGA, ASIC, etc., that
runs PowerPC code.  It is not clear how open it is - do you need to
obtain a zero-cost license?  Can you modify the ISA as you want?  What
about naming - can you call it a PowerPC processor or PPC compatible,
even if you add things to it?  What about if you remove features?  Will
groups other than IBM, Apple and NXP be involved in the future of
PowerPC and its ISA?

It does not appear that they are giving away a usable /implementation/
of a PowerPC core.

I'm guessing answers to all these points are to be found with a bit of
research on the Linux Foundation or IBM's websites, but they need
considered before it is clear what IBM have actually done here.


> 
> (E.g. see here and other links:)
> https://www.eejournal.com/article/ibm-gives-away-powerpc-goes-open-source/)
> 
> 
> As PowerPC processors do are used in embedded devices, anybody any idea
> what this would mean for the embedded-processor market?

Mostly nothing, I think.

PPC cores are used in a few specific embedded markets - primarily the
automotive industry, and other tough industrial uses.  They used to be
popular in networking systems (along with MIPS), but ARM is taking over
that niche.  I think you will continue to get PPC-based devices from
those that made them before (primarily NXP, with some second-source
devices from ST).  I don't think anyone is going to design a new
implementation for new devices unless they are already invested in the
PPC world.  PPC simply does not have any advantages over alternatives,
and it is a big and heavy ISA compared to RISC-V.

What you might see is a few more second-source parts, perhaps also
things like radiation-hard or high-temperature versions from folks like
Atmel.  And you might see it in use in systems that need a very fast
processor and are willing to spend a lot of effort to get it, but want
low production or licensing costs - maybe we'll see it again in games
consoles, or chips designed specifically for supercomputers.

> Are we now going to be flooded by Chinese ppc-based devboards?
> And is this going to kill the risc-v?
> 

No, it won't kill RISC-V.  It will (in my humble and only somewhat
informed opinion) aid RISC-V, by making "open source ISA" more
acceptable to conservative and sceptical companies who viewed "open
source ISA" as meaning "made by hobby developers" or "made by
communists".  When IBM says "open source ISAs are good", they are more
likely to take note of other open source ISAs.

> 
> 
> BTW.
> Does anybody have an easy-to-use overview of different powerPC
> architectures out there? (especially for embedded use)

I'd be surprised if such a thing exists.  There are /many/ PPC variations.

> 
> I've been trying to understand the different wikipedia pages on the
> powerPC architectures, but it all seams to one giant mix of names,
> numbers and 'books' from a dozen different companies.
> 
> 
> 
> Cheerio!
> Kr. Bonne,
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