On Mon, 15 Oct 2001 [EMAIL PROTECTED] wrote: > On 14 Oct 2001, at 13:40, Francois Gouget wrote: [...] > 20% cooler = 60K? There should be frost on the heatsink ... > > Do you mean 20% less power consumption? That seems reasonable.
Good point, I mixed up. and it's definitely not the same :-) > Denser circuits allow lower voltages which does result in a lot less > power consumption per element. But there's less area for the > waste heat to get out, so the cooling problem doesn't neccessarily > go away... Still usually when the process shrinks and the frequency stays the the chip runs cooler too. I believe this is the case of the new Tualatin P3. > > This poses a kind of dilemna since the energy used to run prime-net > > is no longer energy that would have been wasted otherwise. So you have > > to make a choice between preserving the environment and running > > prime-net (to some extent). > > This is the case with most if not all of the mainstream PC CPUs > made in the last couple of years. If you don't use the floating point > unit the FPU turns itself off, there is a large drop in current draw > and the CPU cools down. Alternatively, with many "micro" desktop > & laptops, you need to turn on an extra fan if you run programs > which exercise the FPU (as Prime95/mprime undoubtedly does). > > The CPU current consumption of a 1.2GHz T'bird will drop by > ~30W when the FPU is inactive. However, given that the power > drawn by the system as a whole is likely to be >150W (_much_ > more if you have a large CRT monitor), the power saving by the > system as a whole is not likely to be hugely significant. True. It's just even more pronounced with processors like the K6 and the new Athlons: I believe they adjust the processor frequency dynamically, kind of like the Transmeta ones. So it's the power economies are realized on the whole processor, not just a specific unit. It's also why I don't run prime-net on my laptop (a P3-600): I like to keep it quiet which means getting it idle so that the CPU fan is stopped. [...] > > > Note particularly that e.g. 256 MB can be made up of one bank of 256 > > > MBit, two banks of 128 MBit or four banks of 64 MBit RAM chips; > > > expect a performance difference of 5% - 7% between these > > > configurations even if the chip access speeds & timings are > > > identical. More banks are faster. > > > > Hmmm, you need to distinguish motherboards that merely have > > multiple > > memory slots, from motherboards that have more than one data path to > > the memory. The only motherboards that I know of that can do the > > latter are some RDRAM based motherboards and the Nvidia nForce. > > In all other cases (the more common one?) putting multiple DIMMs > > should not affect performance one way or another. > > No, this is the construction of individual DIMMs, not occupancy of > DIMM slots, though populating two DIMM sockets with _identical_ > single-bank DIMMs can get you the same performance boost. Ah, I understand what you meant now. I thought all DIMMs were multi-banked (potentially even holding all banks in just one chip?). > > Yes, AMD better implement SSE2 in their processors soon. > > Why? Might there not be a better way? SSE2 seems to be a good extension to the x86 instruction set. It looks like it does wonders for prime-net anyway. And since I expect most applications to target SSE2 rather than 3DNow... As for whether it's really useful in everyday life it's another matter. But for applications that do lots of floating point operations it seems worth it. -- Francois Gouget [EMAIL PROTECTED] http://fgouget.free.fr/ Demander si un ordinateur peut penser revient � demander si un sous-marin peut nager. _________________________________________________________________________ Unsubscribe & list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
