OOO hw vs SW&in-order hw

By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), October 2, 2009 6:11 am
Room: Moderated Discussions
Pun Zu (asdfd@sdf.fd) on 10/2/09 wrote:
>
>How about of you look at it a business case? Can you
>justify Intel’s choice with Atom design?

The business case is trivial - Intel knew (and knows)
that they had a big gaping hole in their product map. They
needed to try to fill that.

That trivial and obvious business case has absolutely no
bearing on the actual technical side, and doesn't validate
(or invalidate) the choice to go with in-order. That choice
was largely independent.

I bet that the reason Atom is in-order is that it was done
by people who had a much easier time starting from that
base, and didn't have a lot of numbers either way. There
is no "business case" in that discussion - the business
case is what then allowed the project to actually go ahead,
not what decided any technical details.

And remember, the business case was also fairly weak, in
the sense that yes, Intel knew it had a huge gaping hole
at the really low power side, and yes, Intel knew that
there clearly was a market there (ARM is unquestionably a
large market even by Intel standards!), but at the same
time nobody inside Intel could guarantee that they would
be able to get into the market. They are not historically
good at SoC kind of designs, and they must know that.

So from a business perspective, it was a clear opportunity,
but it was also a somewhat risky one. You'd want to test
the waters with the easiest possible approach. Add to that
a group of people who probably wanted to try re-doing a
Pentium core with modern technology (they probably had some
people who had been involved with the original Pentium) as
a skunk-works project, and what do you get?

Right. You get Atom. You get a pretty weak chip that never
likely had a lot of serious analysis done on it, and with
chipsets that were clearly not thought out, but tacked
on later. And despite those clear and huge issues,
it ends up being a relative success!

So what does Intel do now?

One thing Intel does is the CULV chips. Sure, they would
likely have done them even without Atom, but I think that
one thing that Atom showed was that people wanted cheap
thin-and-light laptops ("netbooks"). Right now, in that
market, the best choice is almost certainly one of the
CULV CPU's, not Atom.

The other thing Intel needs to do - and hasn't done yet -
is fix the chipset situation for whatever next-gen Atom.
Right now, you can either get the venerable GMA950, which
is fine but pairs much better with one of the CULV chips.
Or you can get a GMA500-based thing, which apparently will
not run Windows to satisfaction, and which has a horrible
driver situation under Linux.

Or you can do the crazy ION thing, which means that more
of the money goes to nVidia than Intel, and considering
the track record is pretty risky anyway. Right now, any
sane person would likely avoid nVidia chips for anything.

So from a technical and business standpoint, the
chipset is the biggest problem with Atom. But at the same
time, you need to keep the original goal in mind: it wasn't
netbooks or cheap laptops, it was the ARM market. And in
that market, the direct competitor to Atom is going to be
Cortex-A9.

And dammit, you can be one of the crazy people who think
that Out-of-Order is "too complex" or "too power-hungry",
but even the crazies tend to admit that OoO performs a lot
better.

So the business case becomes absolutely trivial: do you
want to be competitive with Cortex-A9 or not? Forget the
netbook market: the CULV chips are largely perfectly
adequate for the higher end there. Look at the market that
Intel wants to get into: the MID/tablet market and
high-end phones.

And quite frankly, the way Cortex-A9 looks, I think Intel
has two choices:

(a) just give up

(b) put some real resources on Atom, and admit that they
need more than a hacked-up Pentium-like core.

Those are the choices. And I don't think in-order really
is part of (b). I seriously doubt they can beat Cortex-A9
with in-order. The x86 architecture is an advantage in
some market, and maybe it's enough of an advantage that
slower than Cortex-A9 is fine, but quite frankly, in most
of those markets the CULV parts are going to continue to
be a good choice.

So they do need at least performance parity with
Cortex-A9. Now, the common Cortex-A9 is certainly not going
to be 2GHz, it's likely going to be 600-800MHz, simply
because of power issues. So yes, even a current Atom at
1.6GHz will likely beat that (although I suspect it's close)
but that's ignoring power issues. You need to be in the
tens or hundreds of mW, not in the 1.5W space.

That means tons of engineering, no matter how you
look at it. Atom's current performance may be acceptable,
but power use is off by about an order of magnitude.

I'm sure they can get a factor of two just from process,
and from tweaking stuff. Maybe even more. But they'd still
be off by a lot, even just on the core side.

So what I'd do if I were Intel is look very seriously at
alternate designs. One of them would be to aim for at least
IPC parity with Cortex-A9, and run at much lower frequencies
than Atom does now. That has the advantage that they could
also scale up the frequency, something that they almost
certainly cannot do with Atom (3GHz Atom, anyone? Sure,
it's possible, but it would suck compared to the
CULV parts)

And I don't think you can do that without OoO.

Linus
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TopicPosted ByDate
Thoughts and questions on the Cortex A9Gabriele Svelto2009/09/26 01:46 AM
  Thoughts and questions on the Cortex A9none2009/09/26 02:27 AM
    Thoughts and questions on the Cortex A9jeff2009/09/27 04:06 AM
      Thoughts and questions on the Cortex A9Michael S2009/09/27 04:29 AM
        Thoughts and questions on the Cortex A9none2009/09/27 05:01 AM
          Thoughts and questions on the Cortex A9Howard Chu2009/09/27 09:39 AM
      Thoughts and questions on the Cortex A9Wilco2009/09/27 06:03 AM
        Thoughts and questions on the Cortex A9jeff2009/09/27 07:00 AM
          Thoughts and questions on the Cortex A9a reader2009/09/27 07:17 AM
            Thoughts and questions on the Cortex A9David Kanter2009/09/27 07:37 AM
              Thoughts and questions on the Cortex A9a reader2009/09/27 07:46 AM
                Thoughts and questions on the Cortex A9Mat2009/10/01 12:04 PM
                  Thoughts and questions on the Cortex A9Wilco2009/10/01 05:09 PM
                    Thoughts and questions on the Cortex A9anon2009/10/01 07:19 PM
            Thoughts and questions on the Cortex A9RagingDragon2009/09/28 04:11 PM
          Thoughts and questions on the Cortex A9Linus Torvalds2009/09/27 08:05 AM
            OOO hw vs SW&in-order hwno thanks2009/09/27 03:47 PM
              OOO hw vs SW&in-order hwLinus Torvalds2009/09/28 05:22 AM
                OOO hw vs SW&in-order hw?2009/09/28 10:37 AM
                  OOO hw vs SW&in-order hwRagingDragon2009/09/28 04:22 PM
                  OOO hw vs SW&in-order hwMegol2009/09/29 03:35 AM
                OOO hw vs SW&in-order hwAnders Jensen2009/09/28 10:50 PM
                  OOO hw vs SW&in-order hwLinus Torvalds2009/09/29 06:44 AM
                    OOO hw vs SW&in-order hwMark Roulo2009/09/29 08:58 AM
                      OOO hw vs SW&in-order hwLinus Torvalds2009/09/29 09:30 AM
                        3- and 4-issue in-order CPUsMark Roulo2009/09/29 10:06 AM
                          3- and 4-issue in-order CPUsLinus Torvalds2009/09/29 10:29 AM
                          3- and 4-issue in-order CPUsGian-Carlo Pascutto2009/09/29 11:35 PM
                          3- and 4-issue in-order CPUsMichael S2009/09/30 01:01 AM
                    OOO hw vs SW&in-order hwmpx2009/09/30 03:14 AM
                    OOO hw vs SW&in-order hwPun Zu2009/10/02 01:44 AM
                      OOO hw vs SW&in-order hwnone2009/10/02 04:22 AM
                      OOO hw vs SW&in-order hwLinus Torvalds2009/10/02 06:11 AM
                        OOO hw vs SW&in-order hwa reader2009/10/02 08:30 AM
                          OOO hw vs SW&in-order hwLinus Torvalds2009/10/02 08:59 AM
                            MoorestownDavid Kanter2009/10/02 09:59 AM
                              What's the difference between Moorestown and Pine Trail cores?anon2009/10/03 07:37 PM
                              Moorestownnone2009/11/03 03:34 PM
                                MoorestownAnon2009/11/04 02:17 PM
                                  Moorestownnone2009/11/05 12:38 AM
                                    MoorestownDavid Kanter2009/11/05 03:45 PM
                                      MoorestownIntelUser20002009/11/06 03:17 AM
                                      MoorestownAnon2009/11/06 12:51 PM
                                        Moorestownnone2009/11/07 06:07 AM
                            OOO hw vs SW&in-order hwAnon2009/10/02 06:55 PM
                              Cluebat for graphicsDavid Kanter2009/10/02 08:19 PM
                                Cluebat for graphicsAnon2009/10/03 04:45 PM
                                  Cluebat for graphicsDavid Kanter2009/10/04 12:57 AM
                                    Cluebat for graphicsAnon2009/10/04 07:15 PM
                                      Cluebat for graphicsDavid Kanter2009/10/05 02:09 AM
                                        Cluebat for graphicsAnon2009/10/05 02:36 PM
                                          Cluebat for graphicsDavid Kanter2009/10/05 08:54 PM
                                            Cluebat for graphicsAnon2009/10/06 04:58 PM
                              OOO hw vs SW&in-order hwLinus Torvalds2009/10/03 05:58 AM
                            OOO hw vs SW&in-order hwslacker2009/10/02 08:11 PM
                            Linux graphics driversRagingDragon2009/10/03 07:27 PM
                              Linux graphics driversanon2009/10/04 06:15 AM
                                Linux graphics driversnone2009/10/04 09:12 AM
            Thoughts and questions on the Cortex A9jeff2009/09/27 05:31 PM
        Thoughts and questions on the Cortex A9someone2009/09/27 08:30 AM
          Thoughts and questions on the Cortex A9none2009/09/27 09:09 AM
            Thoughts and questions on the Cortex A9Wilco2009/09/27 10:35 AM
              Thoughts and questions on the Cortex A9someone2009/09/27 10:55 AM
                Thoughts and questions on the Cortex A9Wilco2009/09/28 01:08 AM
                  Thoughts and questions on the Cortex A9someone2009/09/28 04:58 AM
                    Thoughts and questions on the Cortex A9none2009/09/28 05:18 AM
                      Thoughts and questions on the Cortex A9someone2009/09/28 06:35 AM
                    Thoughts and questions on the Cortex A9Wilco2009/09/28 07:25 AM
                      Thoughts and questions on the Cortex A9Michael S2009/09/28 10:02 AM
                        Thoughts and questions on the Cortex A9Wilco2009/09/29 12:35 AM
                    Thoughts and questions on the Cortex A9Chuck2009/09/28 06:15 PM
              samplesAM2009/09/27 10:20 PM
                samplesWilco2009/09/28 12:51 AM
                  samplesAM2009/09/28 03:16 AM
              Shrinks and process techDavid Kanter2009/09/29 12:22 AM
            Thoughts and questions on the Cortex A9someone2009/09/27 10:42 AM
              Thoughts and questions on the Cortex A9none2009/09/27 11:52 AM
              Atom to stay in-oder or go OoO?AM2009/09/27 10:09 PM
                Atom to stay in-oder or go OoO?Ungo2009/09/28 04:34 AM
                  Atom to stay in-oder or go OoO?a reader2009/09/28 09:15 AM
                    Atom to stay in-oder or go OoO?anon2009/09/28 06:25 PM
                  Atom to stay in-oder or go OoO?AM2009/09/30 02:32 AM
                    Atom to stay in-oder or go OoO?baxeel2009/09/30 07:25 AM
                      Atom to stay in-oder or go OoO?AM2009/09/30 10:12 PM
                    Atom to stay in-oder or go OoO?Ungo2009/10/01 02:00 AM
                      Atom to stay in-oder or go OoO?AM2009/10/01 04:08 AM
                        Atom to stay in-oder or go OoO?anonymous2009/10/01 04:33 AM
                          Atom to stay in-oder or go OoO?AM2009/10/03 06:24 AM
                        Atom to stay in-oder or go OoO?Pun Zu2009/10/02 12:30 AM
                        Atom to stay in-oder or go OoO?Ungo2009/10/02 12:11 PM
                          Atom to stay in-oder or go OoO?AM2009/10/03 06:22 AM
                            Atom to stay in-oder or go OoO?Ungo2009/10/03 01:53 PM
                              Atom to stay in-oder or go OoO?AM2009/10/04 07:44 AM
                                Atom to stay in-oder or go OoO?David Kanter2009/10/04 10:02 PM
                                  Atom to stay in-oder or go OoO?AM2009/10/05 06:18 AM
                                    Atom to stay in-oder or go OoO?David Kanter2009/10/05 10:12 AM
                                      Atom to stay in-oder or go OoO?AM2009/10/06 03:51 AM
                                        Atom to stay in-oder or go OoO?anonymous2009/10/06 06:58 AM
                                        Do you have any proof?David Kanter2009/10/06 08:58 AM
                                          Do you?AM2009/10/06 10:30 PM
                                            Of course I do!anonymous2009/10/07 04:58 AM
                                              Thanks :-)AM2009/10/08 02:17 AM
                                                Thanks :-)anonymous2009/10/08 04:52 AM
                                                  Thanks :-)AM2009/10/09 02:13 AM
                                                    Thanks :-)anonymous2009/10/09 05:03 AM
                                                    Thanks :-)Foo_2009/10/09 05:47 AM
                                                      Thanks :-)AM2009/10/10 12:15 AM
                                            That's what I thought...David Kanter2009/10/07 08:00 AM
                                              That's what I thought...AM2009/10/08 02:26 AM
                                                That's what I thought...anonymous2009/10/08 05:02 AM
                                                  let's see...AM2009/10/09 02:09 AM
                                                    let's see...anonymous2009/10/09 04:43 AM
                                                      let's see...AM2009/10/09 04:52 AM
                                                        let's see...anonymous2009/10/09 05:15 AM
                                                          let's see...AM2009/10/10 12:18 AM
                Atom to stay in-oder or go OoO?someone2009/09/28 05:09 AM
          I call Trollhobold2009/09/28 03:51 AM
            I call Trollsomeone2009/09/28 05:15 AM
              OT: categories of motivation in a forumhobold2009/09/29 05:01 AM
          Thoughts and questions on the Cortex A9Michael S2009/09/28 09:43 AM
            Thoughts and questions on the Cortex A9a reader2009/09/28 03:12 PM
              Thoughts and questions on the Cortex A9someone else2009/09/28 11:25 PM
                Why Cortex A9?hobold2009/09/29 06:20 AM
                  Why Cortex A9?someone else2009/09/29 09:57 AM
                    Why Cortex A9?Richard Cownie2009/09/29 05:09 PM
                      Why Cortex A9?hobold2009/09/29 11:38 PM
                        Why Cortex A9?Richard Cownie2009/09/30 05:49 AM
                          Why Cortex A9?hobold2009/09/30 06:46 AM
                            Why Cortex A9?none2009/09/30 06:56 AM
                              Marvell Sheeva and plug computingRichard Cownie2009/09/30 08:03 AM
                              Why Cortex A9?Michael S2009/09/30 09:07 AM
                                Why Cortex A9?none2009/09/30 09:40 AM
                                Why Cortex A9?Gabriele Svelto2009/09/30 11:43 AM
                                  ARM architectural licenseDavid Kanter2009/09/30 04:57 PM
                                    ARM architectural licensea reader2009/10/01 06:25 AM
                                      ARM architectural licenseRichard Cownie2009/10/01 07:21 AM
                                Why Cortex A9?slacker2009/09/30 06:12 PM
                                  ARM architectural licenseDavid Kanter2009/09/30 06:16 PM
                                  Why Cortex A9?Michael S2009/10/01 06:45 AM
                                    Why Cortex A9?slacker2009/10/02 01:41 AM
                                      Why Cortex A9?Richard Cownie2009/10/02 09:28 AM
                                        Questions...David Kanter2009/10/02 09:56 AM
                                          Questions...Richard Cownie2009/10/02 10:29 AM
                                            Questions...Wilco2009/10/02 12:05 PM
                                          Questions...slacker2009/10/02 07:51 PM
                                        Why Cortex A9?slacker2009/10/02 07:44 PM
                            Why Cortex A9?David W. Hess2009/09/30 07:42 AM
    Thoughts and questions on the Cortex A9Gabriele Svelto2009/09/28 12:28 AM
  Thoughts and questions on the Cortex A9Wilco2009/09/26 06:38 AM
    Thoughts and questions on the Cortex A9Gabriele Svelto2009/09/28 12:38 AM
      Thoughts and questions on the Cortex A9Costanza2009/10/01 02:45 PM
    Thoughts and questions on the Cortex A9sylt2009/09/28 04:54 AM
      Thoughts and questions on the Cortex A9Wilco2009/09/29 12:15 AM
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