x86 and ARM

By: Ungo (a.delete@this.b.c.d.e), November 27, 2020 1:55 am
Room: Moderated Discussions
Chester (lamchester.delete@this.gmail.com) on November 26, 2020 6:38 pm wrote:
> Has anything changed with aarch64 that invalidates Henry's statement? aarch64
> retains user-space compatibility with ARMv7, and still supports features required
> by modern operating systems (paging, exceptions, privilege levels).

This isn't quite how it works.

AArch64 is a 64-bit execution state defined by the ARMv8 spec. It only supports the A64 ISA.

ARMv8-A provides ARMv7 compatibility with the AArch32 execution state, which supports two ISAs, A32 and T32 (Thumb). Transitions between AArch64 and AArch32 only take place as part of transitions between exception levels (privilege levels).

Most relevant to what you're talking about, though, is that support for the AArch32 execution state is optional. Implementors can choose to design ARMv8-A processors which only support the AArch64 state. (They can also choose to do the opposite and support only AArch32.)

Apple stopped implementing AArch32 in the A11 Bionic, and I think there have been announcements of other 64-bit only ARMv8-A cores.
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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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