I think the ATLAS cluster is the best thing in Hannover, after the Alte Rathaus beer, which I tasted after visiting CEBIT while working for Bull. Prosit, Bruce!
CeBit 2008? You should have taken the ATALS cluster tour done by Rittal then.
Bikeman is right, ATLAS is still in commissioning and has not yet contributed to Einstein@home (though it helped in internal tests).
The eScience Group is running Einstein@home tasks in "ordinary" jobs on various Grid clusters. ATLAS isn't one of them, but other supercomputers at AEI (Potsdam) are.
BM

RE: AEI eScience group, for the German Grid (D-Grid)
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I don't know precisely which machines they are using, but I think at least the ones connected in the AstroGrid-D project.
They don't compile their own applications but use the standard Linux Apps from Einstein@home, thus the don't run on BlueGene machines.
BM
BM