Massive CPU Temp changes from nforce2 to kt400

[iranu]

Hi all,

Strange things are occuring here......

I have recently installed an xp2500 in an Asus a7n8x-e deluxe with an arctic cooling copper silent 2 tc heatsink.

http://www.arctic-cooling.com/en/pro..._silent2r2_tc/

using mbm5 and Asus probe I have temperatures of 47°C idle (with good case ventilation) I thought that this was WAY too high compared with my previous cooler master on a xp2800 at stock (30°C idle on MSI KT4 ultra)

so I put the 2500 chip and arctic cooler onto the MSI KT4 ultra board and measured temps using mbm5 and the (very good) MSI pc alert 4. To my surprise both are showing 31°C.

What is going on? Why is there a 16°C difference!!

Vcore is showing 1.63v on pc alert on the MSI board with either crap but reliable old Time computers 250w PSU or my new Tagan 480W.

Vcore on Asus a7x8n is 1.65-1.68 in the bios using Tagan 480W PSU.

Is the Asus overvolting? If it is I don't believe it would cause such a large rise. Gonna try the xp2800 with cooler master heatsink in the asus.

BTW I have had the 2500 o'c to 3200 @ 54°C idle on Asus a7n8x but needed to raise the Vcore from 1.65 to 1.70.

[streetster]

nf2 using the onboard diode, kt4 using an external thermal thermister-type thing perhaps?

[Efaill]

You have come a croper of the fact that different motherboards will be calibrated differently by the manafacturers. There will always be differences. It has also been known that even changing different bioses to change the dispalyed temperature even for the same setup. So the temperature isn't nesseceraliy different just dispalyed so.

[0iD]

Is the temp probe under the socket bent so it's not near the core?

[iranu]

There isn't a temp probe! I thought this board had one but can't remember seeing it last night, bit worse for wear you see. Puters and booze - great combo!!

(iirc the probe should be a small red thing on two wires which sits in the centre of the socket). Perhaps this is the problem

The only thing I can really do is get my old thermocouple and multimeter out and measure the temps on both of the heatsinks! I know that the MSI board is showing 30° ish using both heatsinks so the cooling rate/power is the same.

I'll put the thermocouple on the centre section of the heatsink where the clamp is and see what I get. If the temps are similar then no probs, if not then it's head scratching time.

[BUFF]

There isn't a temp probe! I thought this board had one but can't remember seeing it last night, he temps are similar then no probs, if not then it's head scratching time.

iirc the A7N8X uses the CPU diode.

[StarkMjolk]

If you only tried fitting the CPU once on both mobos, it might be an issue of a missfitted CPU. I've reached above 50C with my old water cooling set, and by refitting it with new thermal paste gotten it under 40C load. It can vary alot if you do it good or not.

The other reason might be the kt400 board having a board sensor, while A7N8X-E uses the CPU diode. Can be a quite big temp. difference.

[SilentDeath]

Its known that different bios settings will keep the cpu at different amounts of idle. idle measurements are the LEAST acccurate way to measure a coolers performance.

If you want acccuracy get your self a max6657 chip (free as samples) follow the instructions on there site and connect it to the cpu diode and your mobos smbus headers.

Thermistors are not accurate. the back of cpus does not conduct heat well and even if the sensor is making very good contact with the back (which is very rare) there will still be atleast 5c of inaccuracy but probably 10-15c..
for amd cpus a thermistor can be placed in a hole on the bottom of the heatsink just outside the core area - but a diode is still a lot better.
Im quite sure the a7n8x doesnt use the diode, atleast I cant rememberseing a chip cable of reading the diode on the board I was looking at a few days ago.

[StarkMjolk]

I know my A7N8X Deluxe 2.0 can show the CPU diode with MBM. Using a vapochill, with insulation under the core, and I still get readings around -12 to -15 full load, which must be the CPU diode (my evaporator is around -19 at the same time).

[SilentDeath]

Do you know what chip it uses? might say in mbm or it will be around the cpu area on the mobo. It wil probably be a winbond chip as they seem to be most common for sensing on mobos.
Reson I ask is Im making a diode-reader circuit for my nf7-s and all I can find is maxim-ic chips, and there all TINY, like 5mm*3mm with 16 pins to be soldered... ok theres some with 8 but they are still v difficult.... (I fryed my last free samples by taking too long to solder them)

[iranu]

After doing quite a bit of browsing it does seem that this mobo does not have the temp probe.

StarkMjolk: I have reseated the heatsinks twice now each on this board so I'm either quite hamfisted or unlucky. lol It was the first thing I did tbh.

I think what I will do isrun prime95 or 3dmark03 on a loop for while and see if it plays up. If it's stable (which it is atm) then I'll look at overclocking a little bit. If I get to the stage where I'm unhappy with the performance then I'll invest in a better heatsink!

SilentDeath: Not sure which chip it uses, sry.