Thanks for the rapid replies, > Eeek, these machines are now in the wild? Didn't realize this :) Yes. They are still ramping up production, and evals are scarce. I am pretty excited about it, because on paper, even without the hyperthreading, they should run pretty fast for I/O intensive workloads. My current eval project is to get some empirical performance numbers on a particular application. > I don't know if anyone ever tried a 2.2.x kernel on these boxes :) I'm first! Lucky me! :-) > Is there a reason you _really_ need a 2.2.x kernel for this machine? Longterm no, shortterm yes, We have some modifications to the 2.2.x kernel/drivers that would cost us some time to migrate to 2.4.x. We expect to do this, but not within the short eval period during which I have the box. My immediate goal is to get it running enough to take performance measurements so we can clearly quantify the cost/benefit of migrating to this box. > You also might try a UP 2.2.x kernel on this box to see if the problem > is in the parsing of the APIC tables (as I think it is.) As a matter of fact, we did try a UP 2.2.x kernel, and it worked. But then we only have one CPU, and where is the fun in that ? :-) So I suppose this gives further support to the mishandled APIC table theory. I am interested and motivated to understand the details of APIC's further. If I were to attempt to patch up a 2.2.x kernel to workaround this problem, what documentation should I have on hand ? I have an Intel SMP 1.4 doc, although I haven't studied it in detail yet. Is this sufficient or are there other Must Have documents that I will need ? - GL