How to tell whether CPU supports x64?

[Devin Teske]

On Thu, 2011-03-17 at 14:33 -0700, Tait wrote:

> I have a remote server, and I'd like to know if it will support
> 64-bit instructions.


I wrote this for the job (please, suggestions/comments very welcome):


############################################################ BEGIN FILE
/* -*- tab-width:  4 -*- ;; Emacs  */
/* vi: set tabstop=4     :: Vi/ViM */

/* Devin Teske (c)2010, July 26, 11:42:38. All Rights Reserved. */

/* system includes */
#include <stdio.h>				/* printf(3) */
#include <stdlib.h>				/* EXIT_SUCCESS exit(3) */
#include <string.h>				/* strncmp(3) */
#include <sys/types.h>			/* u_int/register_t (for machine/cpufunc.h) */
#include <machine/cpufunc.h>	/* read_e/rflags() write_e/rflags()
                            	 * do_cpuid() */
#include <machine/psl.h>		/* PSL_ID */
#include <machine/specialreg.h>	/* AMDID_LM */

/* Preprocessor Macros */

#ifndef AMDID_LM
#define AMDID_LM 0x20000000
#endif

int
main (int argc, char *argv[])
{
	int has_lm = 0;
	char *cpu_vendor;
	int vendor[3];
#ifdef __amd64__
	register_t rflags;
#else
	u_int eflags;
#endif
	u_int regs[4];

	/* Check for presence of "cpuid". */
#ifdef __amd64__
	rflags = read_rflags();
	write_rflags(rflags ^ PSL_ID);
	if (((rflags ^ read_rflags()) & PSL_ID) != 0)
#else
	eflags = read_eflags();
	write_eflags(eflags ^ PSL_ID);
	if (((eflags ^ read_eflags()) & PSL_ID) != 0)
#endif
	{
		/* Fetch the vendor string. */
		do_cpuid(0, regs);
		vendor[0] = regs[1];
		vendor[1] = regs[3];
		vendor[2] = regs[2];
		cpu_vendor = (char *)vendor;

		/* check for vendors that support AMD features. */
		if (strncmp(cpu_vendor, "GenuineIntel", 12) == 0 ||
		    strncmp(cpu_vendor, "AuthenticAMD", 12) == 0)
		{
			/* Has to support AMD features. */
			do_cpuid(0x80000000, regs);
			has_lm = (regs[3] & AMDID_LM);
		}
	}

	printf("x86_64 support: %s\n", has_lm ? "YES" : "NO" );
	exit(EXIT_SUCCESS);
}
############################################################ END FILE

Save the text above into a file named "x86_64.c" and then execute "make
x86_64" without arguments (or, if you prefer to have a static binary,
instead execute "cc -static -Wall -O -pipe -I. x86_64.c -o x86_64".

After you've compiled the utility, execute "./x86_64" and the results
will be either:

    x86_64 support: YES

or

    x86_64 support: NO

--
Devin

(full sig at bottom)


>  Is there some way I can tell? It's running 32-bit
> FreeBSD right now.
> 
> >From dmesg.boot:
> 	Timecounter "i8254" frequency 1193182 Hz quality 0
> 	CPU: Intel(R) Xeon(TM) CPU 2.40GHz (2387.76-MHz 686-class CPU)
> 	Origin = "GenuineIntel"  Id = 0xf29  Stepping = 9
> 	Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
> 	Features2=0x4400<CNTX-ID,<b14>>
> 	Logical CPUs per core: 2
> 	real memory  = 1073676288 (1023 MB)
> 	avail memory = 1041502208 (993 MB)
> 	ACPI APIC Table: <DELL   PE1750  >
> 	FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
> 	cpu0 (BSP): APIC ID:  0
> 	cpu1 (AP): APIC ID:  1
> 
> I've had no luck trying to search for the id/stepping. Would the
> feature list show x64 support?
> 
> _______________________________________________
> freebsd-questions at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> To unsubscribe, send any mail to "freebsd-questions-unsubscribe at freebsd.org"


-- 
Cheers,
Devin Teske

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