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does the the cpu affect the voltage drop from idle to load?

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veryhumid

Member
Joined
Apr 22, 2004
Location
New Hampshire
I asked batboy this earlier, but I am just curious to know if anyone has an explanation. Is the motherboard and power supply the only things that maintain cpu voltage and voltage drop (droop) from idle to load? I find my system has a pretty big drop, I was wondering if it may be my chip. Is it possible some chips would have higher voltage drops than others? Thanks for the input.

batboy :attn:
 
I'd give a qualified yes to that. I say qualified because I'm basing this solely on my limited observations. Under full load I was getting .04-.06v droop with my 2.8c, whereas my 3.2E D0 usually droops .06-.08, with a very rare and very brief .1v droop. This is with a PCP&C 510 psu and a fully sinked and wc'd MAX3.
 
The power consumtion of the chips will affect the amount of the droop, but only as a % -- if you have no droop, it wont for any chip.

~t0m
 
Styyn said:
I'd give a qualified yes to that. I say qualified because I'm basing this solely on my limited observations. Under full load I was getting .04-.06v droop with my 2.8c, whereas my 3.2E D0 usually droops .06-.08, with a very rare and very brief .1v droop. This is with a PCP&C 510 psu and a fully sinked and wc'd MAX3.

yeah i have like a .09 droop when set to certain voltages, .05 for some. what are the rails looking like on your psu when at full load?


thanks for the input everyone!
 
The voltage differential between idle and load is proportional to the current that the CPU draws. The voltage drop on a 2.8C will be less than with a 3.2E because the E chip (a Prescott) draws much more current than a Northwood.

On a side note, the voltage drop is normal; in fact it's part of the operating spec. If a motherboard provides a consistent voltage from idle to load, that's not necessarily a good thing; it can be detrimental to the long-term life of a chip.
 
Come to think of it, I have noticed a greater amount of undervolting with a Prescott compared to a Northwood, so I think Nookie is right about some CPUs pull more power. The thing is, his IC7 Max3 is dropping from like 1.55v idle to maybe 1.5v load (this is with a 1.575v BIOS setting). This is with a Northwood CPU. I've never seen an Abit mobo drop that much before.
 
yeah i am going to kind of rebuild my computer. Put in the old true 430W and try an IC7-G. I'm really asking this because I wonder if my chip maybe damaged.
 
Sorry about the late response. Anyway, as displayed by MBM5, my 12v rail idles at 12.04 and droops to 11.92 under full load. I realize MBM isn't terribly accurate when it comes to voltage readings, so if anyone could tell me the best way and locations for voltimeter readings I can give some more accurate results :)
 
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