Re: Why the 64 bit ISA is better

[Martin Steigerwald <Martin@lichtvoll.de>]

Am Samstag, 19. Januar 2013 schrieb Stan Hoeppner:
> > PS: do you know if, as for 16 bits to 32 bits, there is a the need to
> > switch processor's "mode"?
> 
> Yes.  x86-64 adds 'long' mode which comprises two sub-modes. See the
> Wikipedia page or the x86-64 Architectural Programmer's Reference Manual
> for details.

You can see whether the CPU has this longmode in Linux:

martin@merkaba:~> egrep --colour=always "(model|lm)" /proc/cpuinfo | head -3
model           : 42
model name      : Intel(R) Core(TM) i5-2520M CPU @ 2.50GHz
flags           : 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 ht tm pbe syscall nx 
rdtscp >>> lm <<< constant_tsc arch_perfmon pebs bts nopl xtopology 
nonstop_tsc aperfmperf eagerfpu pni pclmulqdq dtes64 monitor ds_cpl vmx smx 
est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt 
tsc_deadline_timer aes xsave avx lahf_lm ida arat epb xsaveopt pln pts 
dtherm tpr_shadow vnmi flexpriority ept vpid

This is a good way to see whether a CPU is capable of 64-bit stuff.


lspcu also shows the supported modes:

martin@merkaba:~> lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    2
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 42
Stepping:              7
CPU MHz:               800.000
BogoMIPS:              4983.77
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              3072K
NUMA node0 CPU(s):     0-3

Ciao,
-- 
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
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