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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?

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up vote 3 down vote accepted

I'm not sure about OpenFirmware commands, but your PowerMac G5 only has 1 processor since it's a 9,1. I'll edit this later if I can find any. It looks like it's possible in Single User Mode, but I'm not sure about via OpenFirmware.

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Single User mode still requires a viable OS X boot - so booting to OS X would get you CPU information as easily as single user. – bmike Feb 3 at 20:39
@bmike Sadly, yes. I included it anyways since it was the best I could find at the time. – JMY1000 Feb 3 at 21:03
One should be able to display the device tree in the OpenFirmware environment (cf. e.g. this guide). And the device tree should be pretty accurate, I presume. This device tree is also accessible under Linux, i.e. under /proc/device-tree - and there the /proc/device-tree/cpus/ directory only contains 1 CPU and cat /proc/device-tree/model also yields PowerMac9,1. – maxschlepzig Feb 3 at 21:04
@maxschlepzig Sounds like a solution! Add it as an answer – JMY1000 Feb 3 at 21:05

Considering these two pieces of information

processor   : 0
cpu         : PPC970FX

It looks like there is only one physical CPU installed and it is a single-core.

I tried finding out if the motherboard supports two physical CPUs but came up empty:

motherboard : PowerMac9,1 MacRISC4 Power Macintosh 

Hopefully some Mac hardware gurus are floating around here that are familiar with that board :)

The reason I say the CPU is single-core is because Wikipedia states:

The 970MP is a dual-core derivative of the 970FX

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