Why Raspberry Pi mines slower than an x86 PC?

[Pentium100]

I have one BFL Single that I am using to mine. I have tried various computers, including a Raspberry Pi, but for some reason the Raspberry gets a lower hashrate than a PC that is even slower.
Here's the graph of my hashrate, divided into sections based on the controller. The software is BFGMiner 3.6.0


1 - Laptop: Turion64 1.6GHz, 1GB RAM, WindowsXP 32bit
2 - Raspberry Pi model B, Raspbian Wheezy. Not overclocked.
3 - PC: Athlon XP 2000+, 1GB RAM, Windows 2003 32bit
4 - Raspberry Pi again.
5 - PC: Cyrix MediaGX 233MHz, 64MB RAM, Debian Wheezy i486 (lowest power consuming computer I have other than the Raspberry)

As you see, all three PCs get about the same hash rate (and the hashrate is quite even), but the Raspberry Pi is slower (and the hashrate varies quite a lot) even though it is faster than the 233MHz PC (compiling BFGMiner took much longer on that PC than on the Raspberry Pi). All devices, except #3 were connected to the same hub with the same cables and the same Ethernet over Powerline adapter.

So, any reason why x86 seems to be a better choice for BFGMiner than the Raspberry?

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[vm1990]

its pretty interesting but dont forget the pi is based on a mobile so it dosnt have full blown x86 capability (reason you cant run windows on it) it would be interesting to see what cpu usage is on the pi while its mining

might also be interesting to try minepi (dedicated mining version cant remember the correct name but its similar) it should give better performance for the pi to mine

[Pentium100]

CPU usage on the Pi is ~4% when mining, load average is ~0.05.

OTOH, for the current 233MHz PC with 64MB RAM (section 5 on the graph), the CPU usage is 20-30% and load average is 0.35.

I will look into the minepi distribution.

[g3raint]

Minepeon is the distro, I am using on some home miners and it is very stable

Cheers

Geraint

[vm1990]

Minepeon is the distro, I am using on some home miners and it is very stable

Cheers

Geraint

thats the one i was close.....