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RE: Current measurements on powersupply P4 pin

hfavandepas wrote:

. . . your readings are twice as high as my readings.

Sorry, but I don't see how you reach that conclusion. Yesterday, I wrote:

"The current peaked soon after power-up for about 30 seconds at around 1500/1600 ma (though it went off the scale on one occasion), falling by degrees to settle at 330/340 ma when playing.music."

You report readings ranging from 240 to 360 ma. From where I'm sitting, the steady-state (i.e. while playing music) values are pretty much the same.

I repeated the measurements today (I'd left the meter in place.) The steady-state reading has fallen to 320 ma. I'm not getting excited about that - it's a difference of three per cent. (It could be up to 350 ma tomorrow, making it +/- 3%. I'd be delighted if my meter - it's a good one - is accurate to +/- 2% when reading current.)

The 1500 ma peak on a cold restart was still to be seen today, though not for so long. Presumably that's because I'd left the BIOS at clock=140 MHz; Vcore=0.75v. (I wasn't expecting a "Spanish Inquisition".)

You'll see only a short peak if you do a warm restart. To test it properly, you need to store your settings, put the BIOS back to defaults and do a cold start. Then, if you don't get a peak roughly comparable to mine, something funny IS going on.

Whatever, the values you report all lie, give or take, within +/- 100 ma of mine - some are higher, some lower.

(What I didn't report yesterday was that I get a short peak of ~400 ma at the start of each track, presumably as cPlay decodes flac data.)

You don't say what scale you are using (though your data is in amps) or suggest the calibre of your meter. If you are using a 10-amp range, I'd be a little concerned about the accuracy of readings so close to the low end of a low-resolution scale.

You report 0.24 amps running cPlay at 44.1. Are you sure? That's less than three watts - judging by the way it eats batteries, I have a (OK, OK, it's very old) calculator that seems to need more than that.

Seriously, these are very informal "experiments". We have different meters (neither, I'd hazard, recently calibrated) possibly on different scales; neither of us recorded the temperatures of the CPU or the meter or checked how long the device has been running. We are running different software on a different configuration with different target data, etc etc.

I confess I haven't a clue as to how normal manufacturing tolerances might be reflected in crude tests like these.

I just don't see any "Eureka" moments coming from comparing these data - they seem pretty well in line. In short, we can report with reasonable confidence that an under-clocked E7200 chip draws between quarter and half an amp from the P4 line when playing music.

Anything else risks reading into the data what is not there.

Best

Dave


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