Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > alt.os.development > #8338

Re: 64-bit detection

From "Benjamin David Lunt" <zfysz@fysnet.net>
Newsgroups alt.os.development
Subject Re: 64-bit detection
Date 2015-07-10 08:44 -0700
Organization Aioe.org NNTP Server
Message-ID <mnp0oa$c64$3@speranza.aioe.org> (permalink)
References <mnn174$dd$1@speranza.aioe.org> <op.x1jgivqzyfako5@localhost> <mnns78$v0t$1@dont-email.me>

Show all headers | View raw

"James Harris" <james.harris.1@gmail.com> wrote in message 
news:mnns78$v0t$1@dont-email.me...
> "Rod Pemberton" <boo@fasdfrewar.cdm> wrote in message 
> news:op.x1jgivqzyfako5@localhost...

>> (I.e., useful for any of us to know?)
>
> Yes, that would be useful to know.

Please see my reply to Rod.

> I didn't know either but found that there is a CPUID bit for it.
>
>  CPUID[0x8000_0001].EDX[29]
>
> Almost by chance I found the following snippet in an AMD manual 
> (24593-Rev. 3.23-May 2013).
>
>  ; Use CPUID to determine if the processor supports long mode. ;
>  mov eax, 80000000h ; Extended-function 8000000h.
>  cpuid ; Is largest extended function
>  cmp eax, 80000000h ; any function > 80000000h?
>  jbe no_long_mode ; If not, no long mode.
>
>  mov eax, 80000001h ; Extended-function 8000001h.
>  cpuid ; Now EDX = extended-features flags.
>  bt edx, 29 ; Test if long mode is supported.
>  jnc no_long_mode ; Exit if not supported.

This was my conclusion too, though I hadn't found this reference
yet.

Thanks,
Ben

Back to alt.os.development | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

64-bit detection "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-07-09 16:47 -0700
  Re: 64-bit detection "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-09 23:41 -0400
    Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-10 08:30 +0100
      Re: 64-bit detection "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-10 05:17 -0400
        Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-10 13:41 +0100
          Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-12 19:04 +0100
            Re: 64-bit detection "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-13 02:30 -0400
              Re: 64-bit detection "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-13 02:07 -0700
                Re: 64-bit detection "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-13 23:10 -0400
                Re: 64-bit detection "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-14 01:23 -0700
              Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-13 12:34 +0100
                Re: 64-bit detection "Rod Pemberton" <boo@fasdfrewar.cdm> - 2015-07-13 22:50 -0400
                Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-14 08:37 +0100
                Re: 64-bit detection "Alexei A. Frounze" <alexfrunews@gmail.com> - 2015-07-14 01:41 -0700
                Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-14 10:04 +0100
      Re: 64-bit detection "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-07-10 08:44 -0700
      Re: 64-bit detection "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-07-10 10:52 -0700
    Re: 64-bit detection "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-07-10 08:38 -0700
      Re: 64-bit detection "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-07-10 10:58 -0700
  Re: 64-bit detection CN <qmbmnp3799@pacbell.net> - 2015-07-09 23:00 -0700
    Re: 64-bit detection "Benjamin David Lunt" <zfysz@fysnet.net> - 2015-07-10 08:40 -0700
      Re: 64-bit detection "James Harris" <james.harris.1@gmail.com> - 2015-07-10 21:29 +0100

csiph-web