Cannot power up s1200kp on picoPSU like 65w adaptor
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Depends on the board, but an entire Atom system generally runs less than 35 watts, where I've never seen any normal desktop class system pulling under 80 watts. CPU is less than half of total power consumption on systems I've measured. 65W, 3.42A is way under the recommended specs in the spec sheet for that motherboard, it recommends 350 wt.
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what puzzles me is, the PSU is rated at 65W where as the CPU is 35W. with a SSD and RAM, it can't be more than 40~45W in total, right? so the PSU "should" be sufficient to start the board. well, perhaps my assumption is not right, as i've also read from somewhere that it takes more power to start the system than running it, but for this situation to be true i'd expect, say, running a 35W TDP CPU with a mechanical hard drive (say, about 25W to start) totalling 60W excl RAM and others.
and i am pretty sure the PSU isn't defective as it worked on the atom.
TDP means Thermal Design Power. That is the amount of heat dissipated by the CPU. It's not equivalent to the amount of power drawn by the CPU. Furthermore, there are also power conversion losses on the motherboard VRM circuit.
Additionally, Intel does not rate TDP as the maximum heat output. It's the average heat output so you can expect it to be based on approximately 60% to 75% of the maximum heat output possible.
To top it all off, your 65W adapter is rated for 65W total across all the voltage rails. The VRM circuitry on motherboards ride off the 12V rail these days and not all 65W of the PSU goes to the 12V rail. So there might not be enough current from the PSU on the 12V rail to support the boot-up.
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ok then i think i know what to do. worse case is to get another picoPSU like adaptor but rated at 95W…
but before that i should get a kill a watt and connect S1200KP to a normal desktop PSU, measure the power consumption from this. i'd be surprised it draws more than 95w, but what do i know i am only guessing ???
i really thought i did my maths and enough home work before putting up with this plan LOL
will come back with an update probably by this weekend.
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I would be surprised too. The peak power draw will be at switch on though.
Bare in mind that a standard power supply is a lot less efficient than a DC-DC style PSU.
Even an "80+" power supply is only rated at 80% efficiency at the top end of it's power band. At 50W they may well be less than 50% efficient.Steve
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here is my finding measuring at the plug point:
S1200KP + i3 2120T (TDP 35W) with no RAM no SSD at boot up -> 33WThis is using an ancient 180W power supply (probably about ten years old).
When using the 65W DC to DC with just S1200KP + i3 2120T, no boot up even if it's only 33W which is a lot lower than the rated 65W.
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D2500CC (atom) + one stick 4G SO-DIMM + one 320G mechinical 2.5" drive at plug point is 17W. Then added one 3.5" hard drive to crank up the power consumption, it is now 34W at boot and after a few sec drops to 23W.
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Now, this 65W power supply can handle 34W (D2500CC with 3.5" hard drive), why it cannot handle 33W of S1200KP…
Maybe the problem is not wattage but initial power draw (amp) when boot up?
For those who interested to know, I also took measurement of below on S1200KP:
AMD 4GB DDR3 DIMM per stick is roughly 5W each
Intel X25 120G SSD (my only spare drive happens to be a SSD LOL) is merely about 3W at boot up -
Only other possibility I can think of is that the DC PSU does not provide the full set of ATX power rails, which may not be required on the Atom board. 20pin vs 24pin for example.
Steve
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what puzzles me is, the PSU is rated at 65W where as the CPU is 35W. with a SSD and RAM, it can't be more than 40~45W in total, right? so the PSU "should" be sufficient to start the board. well, perhaps my assumption is not right, as i've also read from somewhere that it takes more power to start the system than running it, but for this situation to be true i'd expect, say, running a 35W TDP CPU with a mechanical hard drive (say, about 25W to start) totalling 60W excl RAM and others.
and i am pretty sure the PSU isn't defective as it worked on the atom.
To top it all off, your 65W adapter is rated for 65W total across all the voltage rails. The VRM circuitry on motherboards ride off the 12V rail these days and not all 65W of the PSU goes to the 12V rail. So there might not be enough current from the PSU on the 12V rail to support the boot-up.
I would think this is probably the explaination. i got myself a multimeter yesterday but don't know how to use it :P Looking forward to verify this once i figured out how to use this meter.
BTW just found the spec sheet of the little adaptor, at 12v max is 4a. that should still be sufficient… really need to learn how to use the meter quickly...
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Only other possibility I can think of is that the DC PSU does not provide the full set of ATX power rails, which may not be required on the Atom board. 20pin vs 24pin for example.
Steve
both power supplies are 20 pin + 4 pin, and both motherboards are taking 24 pin + 4 pin. so probably not this…
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today went and got a 135W adaptor solution. this one is with 24 pin + 4 pin. with 24 pin it did not start. with 24 pin + 4 pin finally it started.
interestingly the seller said they had one S1200KP + i3 2100T (mine is 2120T) using the same 65W and it worked.
the 135W solution comes with a huge adaptor…
BTW 2120T with stock fan is very quiet - spinning at a lowly 9xx RPM
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This is the essential point. You need the P4 power cable to make the S1200KP work, however the Pico does not not have a P4 cable. In stead you can use a convertor cable the you connect to the Molex power connector on one side and the the S1200KP on the other side. This should work even with a 65W Pico. In the end with proper power management the whole system should draw less than 20W.
