Frank McCormick wrote: > Bob Proulx wrote: > >You early adopter you. I haven't rebooted my machine to the new > >kernel today yet. :-) And since then I have rebooted. All good here. :-) But not a PAE kernel here since I am using 64-bits. > >I assume that you could select the previous kernel and boot okay? It > >would be a good thing to double blind test. That would be a good A-B > >comparison test. Because it is possible that the old kernel fails to > >boot now. > > Yes, 2.6.38 and 2.6.39 have been booting for months now (and > still boots) without a problem. It was only when PAE was introduced > I started having the no-boot problem Sounds like a kernel bug. I think it justifies a bug report against the kernel. But loss of HT would not be of extreme consequence in my mind. Just a normal bug and not anything more severe. > I have since benchmarked the system informally..and it is VERY > slightly faster with hyper-threading on. I am just curious but how much difference are you seeing? I expect it to be small and application dependent. Nothing on single threaded applications and only 2%-3% on multi-threaded applications? > >That is odd since hyperthreading really has little to do with > >multi-core cpus. It is orthogonal to it. In many ways HT is an Intel > > That's what I thought but the more mysterious thing is why the PAE > kernel boots fine with hyper-threading turned off. It is an important clue. But I don't know the answer. > > Did you *really* have a dual-core? Or did you have a single-core > > with HT enabled? I think probably the latter based upon your > > description so far. > > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca > cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe pebs > bts cid xtpr > ... > What do you make of that ?? Looks like a single-core to me ? The process definitely displays the "ht" flag and should therefore support hyperthreading. Unless you see two sockets and two cpus then I think you actually have a single core cpu with hyperthreading enabled producing the second fake cpu. In which case losing hyperthreading, while still not good, isn't a huge big deal. > I think now I know more about CPU's than I ever wanted to know:) :-) Bob
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