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

From	kristoff <kristoff@skypro.be>
Newsgroups	comp.arch.embedded
Subject	Re: IBM's PPC being open sourced .. what does this mean for embedded devices ?
Date	2019-09-18 00:39 +0200
Organization	A noiseless patient Spider
Message-ID	<qlrnbr$qpp$1@dont-email.me> (permalink)
References	<qlokni$qpk$1@dont-email.me> <qlq4iq$e53$1@dont-email.me>

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David,

On 17/09/19 10:13, David Brown wrote:
>> 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).

That's very correct. The information at this point is very sparse and 
unclear.

It looks like they are currently open-sourcing the ISA, some additional 
interfaces specs and a softcore implementation of the the POWER ISA.

I guess we need to wait and see exactly what the license of all these 
goodies will say.

BTW. For who is interested, there is also an open-source implementation 
of the 64bit ISA called the "microwatt":
https://github.com/antonblanchard/microwatt

I do not know what version of the ISA is implemented, but -if this 
information can help- this project seams to use the POWER8 toolchain to 
(cross-)compile micropython.
Does this say anything about what version of the ISA is implemented.

> 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.

I agree.
Let's wait and see.

>> 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 know. I remember seeing it on the boot screen of Cisco routers.

>> 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.

Can you explain the difference between the "books" and the Power ISA 
versions, as found on the Wikipedia page here:
https://en.wikipedia.org/wiki/Power_ISA

Also, what is the link between a particular core implementation and the 
books / Isa.

E.g. Say you would like to implement a very low-end ppc core for 
embedded applications.
Do you need to implement the full ISA with all its features or are 
certain parts of the ISA optional?

(e.g. Is it mandatory to add a FPU to the core?)

Thanks!

Kristoff

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