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fans start-stop-start when booting
I have noticed with many PCs, when booting, the CPU fan goes on for a few
seconds, stops, then starts again. On some the first start is at full screaming RPM. Why is this so? Some people even think something is wrong with the PC when it behaves thus. |
#2
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fans start-stop-start when booting
wrote in message ... I have noticed with many PCs, when booting, the CPU fan goes on for a few seconds, stops, then starts again. On some the first start is at full screaming RPM. Why is this so? Some people even think something is wrong with the PC when it behaves thus. I don't think there's anything wrong with it. My Acer laptop has done that from day one, and my homebuilt desktop does it quite often. I think it's just the initial start-up of the CPU that triggers it, but why it does it sometimes and not all the time, I can't say. I have noticed that it seems to be more prevalent with the ~2GHz+ CPU's than it was with the older, slower ones. Just an observation, not an explanation :-) -- SC Tom |
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fans start-stop-start when booting
SC Tom wrote:
wrote in message ... I have noticed with many PCs, when booting, the CPU fan goes on for a few seconds, stops, then starts again. On some the first start is at full screaming RPM. Why is this so? Some people even think something is wrong with the PC when it behaves thus. Mine did that and I was initially concerned something was wrong. I just closed the cover and accepted it as normal. I don't think there's anything wrong with it. My Acer laptop has done that from day one, and my homebuilt desktop does it quite often. I think it's just the initial start-up of the CPU that triggers it, but why it does it sometimes and not all the time, I can't say. I have noticed that it seems to be more prevalent with the ~2GHz+ CPU's than it was with the older, slower ones. Just an observation, not an explanation :-) |
#4
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fans start-stop-start when booting
Bill wrote:
SC Tom wrote: wrote in message ... I have noticed with many PCs, when booting, the CPU fan goes on for a few seconds, stops, then starts again. On some the first start is at full screaming RPM. Why is this so? Some people even think something is wrong with the PC when it behaves thus. Mine did that and I was initially concerned something was wrong. I just closed the cover and accepted it as normal. I don't think there's anything wrong with it. My Acer laptop has done that from day one, and my homebuilt desktop does it quite often. I think it's just the initial start-up of the CPU that triggers it, but why it does it sometimes and not all the time, I can't say. I have noticed that it seems to be more prevalent with the ~2GHz+ CPU's than it was with the older, slower ones. Just an observation, not an explanation :-) There are a few things that happen on computers, that require shenanigans like that. I have an AthlonXP motherboard, with an overclock controller chip. When the motherboard first starts, the default VID and FID are sent by the processor pins, to VCore and for multiplier control. The BIOS, on determining this is the "first run", examines the BIOS settings, figures out the user wanted 1.65V for VCore, and a multiplier of 11, and loads those values into the overclock controller chip. The BIOS then asserts RESET and forces a second start. The overclock controller state is maintained between cycles. On the second "run", the desired overclocked state is applied. That's how the Mobile processor I plugged in, could be operated at Desktop speeds, by overriding the defaults. Another reason for funny behavior at startup, is implementation of the "Power Restore" BIOS setting. "Restore on AC Power Loss" = [Power Off] [Power On] [Last State] Some chipsets seem to be missing proper support for that. After the power comes back, the BIOS always runs, it checks to see if the user wanted "Power On", then it continues with the boot if so. The machine shuts off again, if "Power Off" is the desired setting. And it's all because the hardware (chipset) cannot be programmed to ignore the restoration of power. I had one motherboard, where the "double-start" thing, was cured by a BIOS flash upgrade to a later BIOS version. So sometimes this is a "first BIOS release" bug, and it can be fixed. My current motherboard, the one I'm typing on, does "double-start", but only after AC is freshly applied to the machine (after UPS is switched OFF and then ON again). For any "warm" reboots, only a single start is used. And it's not clear what the motherboard design is doing for this one. I doubt this particular hardware uses an overclock controller chip. It would not be needed. Modern processors are tested at several FID and VID points, and must be unconditionally stable when making changes like that, so there is hardly a reason for "excess RESET pulses" to be used. That's so EIST or Cool N' Quiet can be applied up to thirty times a second (processor put in lower power state, regularly). Paul |
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fans start-stop-start when booting
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