[Libre-soc-dev] maybe get ryzen 7950x for faster compilation and avx512

[Jacob Lifshay]

On Mon, Sep 26, 2022, 11:25 Timothy Pearson <tpearson at raptorengineering.com>
wrote:

>
>
> ----- Original Message -----
> > From: "Jacob Lifshay" <programmerjake at gmail.com>
> > To: "Timothy Pearson" <tpearson at raptorengineering.com>
> > Cc: "Libre-Soc General Development" <libre-soc-dev at lists.libre-soc.org>
> > Sent: Monday, September 26, 2022 1:10:52 PM
> > Subject: Re: [Libre-soc-dev] maybe get ryzen 7950x for faster
> compilation and avx512
>
> > On Mon, Sep 26, 2022, 10:30 Timothy Pearson <
> tpearson at raptorengineering.com>
> > wrote:
> >
> >> > I don't have cloud price numbers right now...
> >> >
> >> > Jacob
> >>
> >> Right, I was talking about the cloud pricing.  A quick glance at Alibaba
> >> shows ~$60/mo. for four cores of 3.8Ghz x86,
> >
> >
> > if 4 cores is all we're getting, imho that would be a foolish decision
> -- i
> > already have a 12-core ryzen 3900x that goes up to iirc 4.5GHz.
>
> There are of course other options and pricing plans, and I think you'd
> need to compare the overall costs.  You've said a few times your workload
> is single thread performance dependent, but then you keep saying more cores
> are better.


that's because there are multiple important workloads -- both
single-threaded (simulation, formal proofs, etc.) and highly multi-threaded
(code compilation, running all unittests in parallel, etc.)

  If you're loading all cores, that Ryzen CPU doesn't boost to the high
> 5GHz number any more.


it does stay at around 5-5.1GHz with a all-core load though, which is still
substantially faster than server hardware or POWER9. It also has a
substantial IPC improvement.

  Been there done that with the Family 15h CPUs, and it's still the case
> from what I'm reading with the 7950.
>
> > and I think you'd have to justify the cost savings of having the AMD
> system
> >> under your desk vs. just using an inexpensive lease from Alibaba.  Even
> if
> >> you used the cloud service 24/7 for a year, that would leave over $1000
> >> left over could be put diretly toward new development for LibreSoC, and
> >> when you get to the 1 year or longer level they offer even further
> pricing
> >> discounts.
> >>
> >> If this was a question of true ownership vs. leasing I'd go toward
> >> ownership, but with AMD you're still only leasing parts of the CPU so
> that
> >> doesn't even enter into the equation sadly.
> >>
> >
> > dismissing it as "leasing" is a bit disingenuous imho, AMD isn't
> > realistically taking it back after a few years, I'll still have the
> > hardware and still be able to use it. even if it's proprietary, it's
> still
> > something I get to keep using as long as I please without having to pay
> AMD
> > more later, and I can sell it when I don't want it anymore.
>
> You're still leasing a critical part -- when (not if) AMD drops support,


I'm using linux, it should still work fine after 15yrs, even if not
officially supported by AMD.
In fact, i'm already using unsupported hardware for our gitlab build
server, it's an 8-core bulldozer cpu iirc.

when (again, not if) a security flaw is found in the PSP firmware, it's not
> going to be worth much or even potentially fit for purpose.  Resale value
> in that case is probably scrap value.
>

actually not really, the i7 7700k is just over 5yr old now and is still
worth around 60% of its original launch price.

>
> I'm also fundamentally opposed to purchasing proprietary hardware as part
> of a libre design effort, unless there is no other choice.


because of the 2x single-threaded speedup, i'd estimate a ~30% total
speedup for developing formal proofs and other things that require running
long-running single-threaded tasks as part of writing/testing code. this is
very substantial.

  Saving a bit of time up front, but then having to deal with the system
> integrity issues that said proprietary hardware presents later on may not
> be the best long-term decision.
>

that's true, though the part we'd likely care the most about in terms of
integrity is our source code, git makes reviewing new changes and noticing
force pushes pretty easy.

>
> As before, just my $0.02.  I'm not a decision maker here. :)


Jacob

>