How ubuntu decide SMP should be enabled or not?

[hzpeterchen]

Hi all,

My CPU is AMD Sempron 2800+:
http://en.wikipedia.org/wiki/List_of_AMD_Sempron_microprocessors#.22Palermo.22_ .28Socket_754.2C_D0.2C_E3_.26_E6.2C_90_nm.29

It sounds a single-core cpu, as I haven't find it at AMD cpu lists which
support SMP:
http://en.wikipedia.org/wiki/Symmetric_multiprocessing

My desktop uses ubuntu8.04, and I find it enable CONFIG_SMP
at /boot/config-2.6.24-24-generic.
My cpuinfo is:

processor : 0
vendor_id : AuthenticAMD
cpu family : 15
model : 28
model name : AMD Sempron(tm) Processor 2800+
stepping : 0
cpu MHz : 1607.322
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 1
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt lm
3dnowext 3dnow up lahf_lm ts ttp
bogomips : 3216.87
clflush size : 64

ps results:
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 0.3 2844 1688 ? Ss 12:55
0:01 /sbin/init
root 2 0.0 0.0 0 0 ? S< 12:55 0:00
[kthreadd]
root 3 0.0 0.0 0 0 ? S< 12:55 0:00
[migration/0]
root 4 0.0 0.0 0 0 ? S< 12:55 0:00
[ksoftirqd/0]
root 5 0.0 0.0 0 0 ? S< 12:55 0:00
[watchdog/0]
root 6 0.0 0.0 0 0 ? S< 12:55 0:00
[events/0]
root 7 0.0 0.0 0 0 ? S< 12:55 0:00
[khelper]
root 41 0.0 0.0 0 0 ? S< 12:55 0:00
[kblockd/0]
root 44 0.0 0.0 0 0 ? S< 12:55 0:00
[kacpid]
root 45 0.0 0.0 0 0 ? S< 12:55 0:00
[kacpi_notify]
root 150 0.0 0.0 0 0 ? S< 12:55 0:00
[kseriod]
root 188 0.0 0.0 0 0 ? S 12:55 0:00
[pdflush]
root 189 0.0 0.0 0 0 ? S 12:55 0:00
[pdflush]
root 190 0.0 0.0 0 0 ? S< 12:55 0:00
[kswapd0]
root 231 0.0 0.0 0 0 ? S< 12:55 0:00 [aio/0]
root 1552 0.0 0.0 0 0 ? S< 12:55 0:00
[ksuspend_usbd]
root 1558 0.0 0.0 0 0 ? S< 12:55 0:00 [khubd]
root 1578 0.0 0.0 0 0 ? S< 12:55 0:01 [ata/0]
root 1581 0.0 0.0 0 0 ? S< 12:55 0:00
[ata_aux]
root 2318 0.0 0.0 0 0 ? S< 12:55 0:00
[scsi_eh_0]
root 2319 0.0 0.0 0 0 ? S< 12:55 0:01
[scsi_eh_1]
root 2349 0.0 0.0 0 0 ? S< 12:55 0:00
[scsi_eh_2]
root 2351 0.0 0.0 0 0 ? S< 12:55 0:00
[scsi_eh_3]
root 2638 0.0 0.0 0 0 ? S< 12:55 0:00
[kjournald]
root 2839 0.0 0.1 2412 956 ? S<s 12:55
0:00 /sbin/udevd --daemon
root 3320 0.0 0.0 0 0 ? S< 12:56 0:00
[kpsmoused]
root 4343 0.0 0.0 0 0 ? S< 12:56 0:00
[kjournald]
root 4344 0.0 0.0 0 0 ? S< 12:56 0:00
[kjournald]
root 4636 0.0 0.0 1716 512 tty4 Ss+ 12:56
0:00 /sbin/getty 38400 tty4
......


I have three questions:

1. How ubuntu decide SMP should be enabled or not?
2. Does SMP technology can be only used at Dual-core processor, or only
Dual-core processor can get benefit from SMP technology?

3. If mine cpu is single-core and I enabled SMP, which will happen?


Thank you
Peter Chen