How do I check if a G5 PPC mac has 2 CPUs or not?

When booting it up under Linux (Debian 8) only one CPU seems to be detected:

```
cat /proc/cpuinfo 
processor   : 0
cpu     : PPC970FX, altivec supported
clock       : 1800.000000MHz
revision    : 3.0 (pvr 003c 0300)

timebase    : 33333333
platform    : PowerMac
model       : PowerMac9,1
machine     : PowerMac9,1
motherboard : PowerMac9,1 MacRISC4 Power Macintosh 
detected as : 337 (PowerMac G5)
pmac flags  : 00000000
L2 cache    : 512K unified
pmac-generation : NewWorld

```

And the kernel should support SMP:

```
uname -a
Linux g5 3.16.0-4-powerpc64 #1 SMP Debian 3.16.7-ckt20-1+deb8u3 (2016-01-17) ppc64 GNU/Linux

```

Does an SMP G5 Macs has 2 heat sinks installed - or is it one big one?

Is there perhaps a OpenFirmware command that lists the CPU details?