x86 and ARM

By: Chester (lamchester.delete@this.gmail.com), November 26, 2020 10:29 am
Room: Moderated Discussions
David Kanter (dkanter.delete@this.realworldtech.com) on November 22, 2020 11:01 pm wrote:
> > > I think you need to look at what folks were saying at that time.
> > >
> > > For example, many people claim ARM has intrinsic advantages over x86. I was staking
> > > out positions many didn't and don't agree with. Specifically, that ARM has no real
> > > advantages over x86 for high performance cores (but does for small ones).
> >
> > Actually David if you look at the high performance Apple A13 vs Zen 2 (3950X) they have similar scores
> > on GB5 and are on similar processes yet the A13 is much more power efficient, retaining the ARM advantage.
> > Even with Zen 3 getting 23% higher scores on GB5 it is still in the same power efficiency ballpark as Zen
> > 2. x86 just cannot approach the power efficiency of ARM at any processor core performance level.
>
> As others pointed out, comparing a desktop-focused chiplet to a
> smartphone SoC makes for unrealistic power comparisons at best.
>
> Also, Geekbench isn't a good benchmark.
>
> Last, you should tell that to all the architects who have designed x86 and ARM processors.
> They will tell you - for a high-performance core, there is very little difference. That includes
> folks working (or previously working) at Apple, ARM, and many other companies.
>
> David

https://tspace.library.utoronto.ca/bitstream/1807/80713/1/Wong_Henry_T_201711_PhD_thesis.pdf is a good read.
Surprisingly, modern ARM instruction sets are not much simpler than x86, despite being called “RISC”. The ARM instruction set also needs decoding into micro-ops. The ARM memory system is similar to x86, supporting unaligned data accesses and hardware TLB miss handling. Unlike x86, ARMv7 also allows predication of most instructions and an implicit barrel shift of one operand for most arithmetic instructions, which are features that are difficult to implement in out-of-order processors. On the other hand, one particularly complex-to-implement feature of x86 is variable instruction length where the length is non-trivial to compute (1 to 15 bytes), while ARM Thumb’s variable-length instructions only have two possible lengths (2 or 4 bytes).
...
While x86 is more complex, the extra complexity due specifically to x86 is modest — much of the complexity of supporting an operating system (supporting exceptions, paging, privilege levels, etc.) is common to most instruction sets


So yeah, X86 is more complex. But once you're designing a complex, OOO core that supports everything a modern OS demands, X86's extra complexity is a drop in the bucket.
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David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon2020/11/19 07:17 PM
  David Kanter RWT article: "Why Apple Won’t ARM the MacBook"tarlinian2020/11/19 07:21 PM
  The article was spot on. Not possible in 2012-2014. Could become possible around 2016-2021.Jouni Osmala2020/11/19 10:29 PM
    The article was spot on. Not possible in 2012-2014. Could become possible around 2016-2021.anon2020/11/20 02:25 PM
  You're intellectually bankruptDaniel B2020/11/20 02:51 AM
    You're intellectually bankruptMichael S2020/11/20 05:22 AM
  David Kanter RWT article: "Why Apple Won’t ARM the MacBook"NaNon2020/11/20 04:08 AM
  He was right. ARM MBs weren't viable until 2019-2020, 8 years later (NT)JRB2020/11/20 08:34 AM
  David Kanter RWT article: "Why Apple Won’t ARM the MacBook"Rayla2020/11/20 09:37 AM
    David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon2020/11/20 02:26 PM
  David Kanter RWT article: "Why Apple Won’t ARM the MacBook"Jon Masters2020/11/20 10:24 AM
    David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon2020/11/20 02:31 PM
      David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon22020/11/20 04:57 PM
        David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon2020/11/20 09:29 PM
          David Kanter RWT article: "Why Apple Won’t ARM the MacBook"Jose2020/11/21 08:48 AM
    David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon22020/11/20 04:54 PM
      David Kanter RWT article: "Why Apple Won’t ARM the MacBook"Jan Vlietinck2020/11/20 11:23 PM
        David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon22020/11/21 12:41 AM
          David Kanter RWT article: "Why Apple Won’t ARM the MacBook"Jan Vlietinck2020/11/21 01:52 AM
            David Kanter RWT article: "Why Apple Won’t ARM the MacBook"anon22020/11/21 03:12 AM
              David Kanter RWT article: "Why Apple Won’t ARM the MacBook"Jan Vlietinck2020/11/21 03:25 AM
        Happy with my historical record :)David Kanter2020/11/21 09:30 AM
          Happy with my historical record :)Per Hesselgren2020/11/21 01:09 PM
            Happy with my historical record :)Maynard Handley2020/11/21 02:02 PM
              Happy with my historical record :)anon2020/11/22 12:23 AM
                Happy with my historical record :)anon22020/11/22 01:13 AM
                  Happy with my historical record :)Michael S2020/11/22 03:12 AM
                    Happy with my historical record :)anon2020/11/22 10:53 AM
                    Swift is 3-wide + custom layout (NT)vvid2020/11/23 04:59 AM
                      Swift is 3-wide + custom layoutanon2020/11/23 02:14 PM
                        No.Heikki Kultala2020/11/23 03:40 PM
                Happy with my historical record :)rwessel2020/11/22 09:14 AM
            Happy with my historical record :)David Kanter2020/11/21 02:51 PM
              Happy with my historical record :)Per Hesselgren2020/11/22 12:28 AM
                Happy with my historical record :)Dummond D. Slow2020/11/22 12:39 PM
                  Is ARM32 native in ARM64?Per Hesselgren2020/11/22 10:34 PM
                    Is ARM32 native in ARM64?Per Hesselgren2020/11/22 10:47 PM
                    Is ARM32 native in ARM64?vvid2020/11/23 06:48 AM
                      Is ARM32 native in ARM64?Per Hesselgren2020/11/23 07:15 AM
                        Is ARM32 native in ARM64?vvid2020/11/23 12:24 PM
                      Is ARM32 native in ARM64?Wilco2020/11/23 11:10 AM
                        Is ARM32 native in ARM64?vvid2020/11/23 01:21 PM
                          Is ARM32 native in ARM64?Per Hesselgren2020/11/23 01:54 PM
          Happy with my historical record :)anon2020/11/21 05:09 PM
            Happy with my historical record :)David Kanter2020/11/21 08:12 PM
          Happy with my historical record :)Emil Briggs2020/11/22 05:11 AM
          Happy with my historical record :)juanrga2020/11/22 08:22 AM
            Happy with my historical record :)Wilco2020/11/22 10:34 AM
              Happy with my historical record :)Dummond D. Slow2020/11/22 12:26 PM
                Happy with my historical record :)Dummond D. Slow2020/11/22 12:42 PM
          Happy with my historical record :) - but should you be?anon2020/11/22 02:35 PM
            Happy with my historical record :) - but should you be?anon.12020/11/22 03:42 PM
              Happy with my historical record :) - but should you be?Foo_2020/11/23 01:14 AM
                Happy with my historical record :) - but should you be?anon.12020/11/23 02:19 PM
            Happy with my historical record :) - but should you be?anon22020/11/22 04:24 PM
            Happy with my historical record :) - but should you be?David Kanter2020/11/22 11:01 PM
              Process technologyDavid Kanter2020/11/23 07:51 AM
                Process technologyDummond D. Slow2020/11/23 08:56 AM
                  Process technologyWilco2020/11/23 11:59 AM
                Process technologyDoug S2020/11/23 12:08 PM
                  Process technologyDummond D. Slow2020/11/23 12:24 PM
                  Process technologyDavid Kanter2020/11/23 05:17 PM
                    Process technologyDoug S2020/11/24 10:09 AM
                      Process technologyDavid Kanter2020/11/24 06:54 PM
              x86 and ARMChester2020/11/26 10:29 AM
                x86 and ARMMaynard Handley2020/11/26 01:05 PM
                x86 and ARMdmcq2020/11/26 02:31 PM
                  x86 and ARMChester2020/11/26 06:38 PM
                    x86 and ARMnone2020/11/27 12:07 AM
                      x86 and ARMJames2020/11/27 01:51 AM
                        x86 and ARMChester2020/11/27 05:22 PM
                          x86 and ARMMark Roulo2020/11/27 07:18 PM
                            x86 and ARMJames2020/11/28 03:22 AM
                            x86 and ARMWilco2020/11/28 06:54 AM
                              x86 and ARMSimon Farnsworth2020/11/30 02:20 AM
                            x86 and ARMgallier22020/11/29 11:42 PM
                          x86 and ARMWilco2020/11/28 06:46 AM
                            x86 and ARMChester2020/11/28 10:28 PM
                              and you don't understand the difference between 1995 and 2001 it seems (NT)anon2020/11/28 11:24 PM
                                sure, early 2000s thenChester2020/11/29 06:31 AM
                                Yes he doesHeikki Kultala2020/11/29 04:24 PM
                                  so not just any random binary (NT)anon2020/11/29 10:08 PM
                            x86 compatibility with 16-bit modesRob Thorpe2020/11/30 06:29 PM
                      x86 and ARMWilco2020/11/27 03:46 AM
                        x86 and ARMChester2020/11/28 10:46 PM
                          x86 and ARMJan Vlietinck2020/11/29 12:21 AM
                            x86 and ARMjuanrga2020/11/29 04:44 AM
                              x86 and ARMChester2020/11/29 06:30 AM
                                I didn't write that ARM is 7 times more efficient than x86. Don't make things up (NT)juanrga2020/11/29 08:04 AM
                                x86 and ARMDoug S2020/11/29 09:26 AM
                                  x86 and ARMwumpus2020/11/29 10:06 AM
                                  x86 and ARMDummond D. Slow2020/11/29 11:59 AM
                                    x86 and ARMjuanrga2020/11/30 01:28 AM
                                      x86 and ARMAdrian2020/11/30 04:50 AM
                                        x86 and ARMJan Vlietinck2020/11/30 06:04 AM
                                          x86 and ARMjuanrga2020/12/01 04:09 AM
                                        x86 and ARMDoug S2020/11/30 11:50 AM
                                      x86 and ARManon.12020/11/30 05:27 AM
                                        x86 and ARManon2020/11/30 08:33 PM
                                          x86 and ARManon.12020/12/01 07:11 AM
                                            x86 and ARManon2020/12/01 02:28 PM
                                              x86 and ARManon.12020/12/01 06:44 PM
                                      x86 and ARMDummond D. Slow2020/11/30 08:04 AM
                                      x86 and ARMGionatan Danti2020/11/30 08:44 AM
                                        x86 and ARMFoo_2020/12/01 12:26 AM
                                          x86 and ARMGionatan Danti2020/12/01 10:01 AM
                                        x86 and ARMjuanrga2020/12/01 04:17 AM
                    x86 and ARMUngo2020/11/27 01:55 AM
                    x86 and ARMjuanrga2020/11/27 03:58 AM
              Happy with my historical record :) - but should you be?anon2020/11/30 02:30 PM
                Happy with my historical record :) - but should you be?David Kanter2020/11/30 04:15 PM
                Happy with my historical record :) - but should you be?anon22020/12/01 03:22 AM
                  Happy with my historical record :) - but should you be?anon2020/12/01 02:16 PM
                    Happy with my historical record :) - but should you be?Maynard Handley2020/12/01 02:38 PM
                      Happy with my historical record :) - but should you be?Gabriele Svelto2020/12/08 07:51 AM
          Happy with my historical record :)Jan Vlietinck2020/11/23 12:55 AM
            Happy with my historical record :)anonymou52020/11/23 03:44 AM
              Happy with my historical record :)Jan Vlietinck2020/11/23 06:16 AM
                Happy with my historical record :)David Kanter2020/11/23 07:18 AM
                  Happy with my historical record :)Jan Vlietinck2020/11/23 09:37 AM
                  Happy with my historical record :)Ungo2020/11/23 08:48 PM
                  Happy with my historical record :)Maynard Handley2020/11/23 09:01 PM
                    Happy with my historical record :)Dummond D. Slow2020/11/24 07:48 AM
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