Electronics > Beginners
oem atx power suply noise and ripple measurment
magic:
10MHz is enough, those PSUs run at tens or hundreds of kHz. 50ms sampling, not really.
11,8V is still within spec.
Changing a 98W CPU to a 65W one is unlikely to make anything worse. Motherboard doesn't matter, all motherboards with the 4-pin connector power the CPU from 12V.
kokodin:
4 pin :D New mobo has 8 pins 12v :] , but i get the point. Motherboard support more powerful cpu's so 8 pin might be better but in most cases they are connected internally anyway. Also tpd does not always mean the same thing nowdays from cpu to cpu.
It isn't a power draw anymore but some crazy thermal equation with multiple variables.
The thing with my test motherboard was, when i get it new it was rated to support 400w psu's and up. Even if my total system power draw was 90W at the time (idle), it destroyed 2 350w power suplies (modecom brand) within a month and i didn't even had a graphic card. It was 2 computers ago though.
So this motherboard might be a very funny test rig by itself (does not monitor 5v rail though).
magic:
It's 2019, I bet you can find reviews with precise measurements of power draw of that CPU if you look around.
Even considering creative marketing, I doubt that 65W rating today is much worse than 98W ten years ago.
kokodin:
Ok i was tired after work, but i did some extra tests and i might know where the problem is.
I didn't have time to pull out a scope yet, but counting on onboard voltage monitoring isn't much help either. So i hooked up my everyday uni-t139c to molex and set it to min max mode.
Meter showed only 0,04V min max , so the load and ironious measurments might not be related to power suply side of things.
Also prime95 set to maximum power draw does not move the voltage graph from the base level, only graphic card load does.
Going further i made an oem atx 24 to standard atx 24 extension cable. But it was really like making atx 20 to atx 24 extension. There is still only single yellow cable going from power suply to the motherboard (not counting cpu power), only it splits in 2 on the connector, so i guess this might act like a resistor. Graphic card might just be draining what little juice motherboard gets.
Tomorow i will try to desolder oryginal oem atx power cable from the pcb and replace it directly with full atx 24 cable, Extension plug was looking ugly anyway. Then i will check again if i still have voltage drops in the software . If i still have them i bring out a scope from storage and play around with that on the weekend. But it might just be that either i had bad connection in extension cable or that 1 to 2 cable split wasn't enough to carry enough current without saging a bit. There is always a chance that the motherboard itself is badly designed.
kokodin:
Multimeter measurment after swaping power connectors
molex
12.05V idle
12.01V full load
on atx connector on the board under load
11.95V
min max 0.1V
seems to be in specs
But i must say replacing all the cables was a nightmare. I had to drill them out instead of desoldering because they bere crimped into groups.
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