Wrong temp reports: MSI 645 Ultra or P4-1.6A??

My retail box P4-1.6A runs fine at 140mhz clock for a speed of 2.1 G in an MSI 645 Ultra (MS-6547 - bios 1.4). Whenever I boot the machine, no matter what the clock speed, MBM5, SANDRA and MSI PC Alert all show CPU temp as 49C. They're all reading off the same mobo sensor, I know. However, the stock heatsink barely seems to get warm. At the highest clock speed, when I run CPU Stability Test for 20 mins, the system temp will rise from around 28-30C to 36C, but the CPU temp only goes from 49C to maybe 51C. The heatsink, in the meanwhile, gets very hot to touch.

At this point, when I reboot & check the BIOS, the CPU temp is just 38C. In 5 minutes, it drops to 34C. Then the BIOS display flickers between 34C and 28C, staying more often at 34C. The reported System Temp in the BIOS appears consistent with the Windows-based software.

If I unplug the cpu heatsink fan, in about 10 minutes it reaches 42C. At that point, when I try to boot into Windows (98SE), the system usually crashes. It will continue to crash till I put the fan back on & wait till the BIOS health temp reads 38C or lower. The point: it should not crash at 42C, which is not that high -- unless the reported temp is wrong.

The gist of all this is that I can't trust the mobo BIOS nor the various Windows-based software to tell the correct CPU temperature.

Which of the following do you think is true?

1. The sensor in the CPU is defective
2. The mobo is not reading the CPU sensor correctly, and the temp shown in the BIOS is incorrect. This also explains why the temps reported by the various software has such a small range.
3. The CPU core gets to operating temp almost immediately, but doesn't affect the heatsink temperature right away.
4. When the CPU is being stressed, its core temp barely rises because the HS transfers the heat away, thereby increasing its own temperature while keeping the CPU cool.

Anyone, any insights??

Either 1 or 2. I have the same board and my CPU temp always reads 49 or 50 degress no matter if I just started it up or it has been crunching for hours. Go to the forums at MSI, everyone seems to have this problem. Other than the temp being incorrect, the board seems to be ok.

Pretty lame they haven't fixed this problem and it's been months, literally. The next time I go to buy a board, I don't think I'm gonna' even look at MSI stuff. I mean, it's a feature they advertise as part of the board, but it doesn't work. Can you say false advertising? lol

Thanks for the info. Yeah, that's really too bad. I guess it must be the mobo or chipset -- I've read of other boards having problems specifically with the NW P4. Is your cpu a NW? The rest of the mobo seems to work fine, tho. Tough to beat for price.

Yeah, even with its temp reading problem, it's hard to beat for the price!

Nope, no Northwood here, just a regular 'ole 1.5.

Hey, I'm using a 2GHz P4 Northwood and I get the same reading in temps. I pretty sure the bios is correct though. The problem with the fan when you unpluged it, is I think you have to have a fan plugged in or your comp won't boot. I think that is how it is with the newer P4 boards.

Hey check my thread. It's about volt modding the MSI Ultra 645

Don't think the unplugged fan has anything to do with it. Everyone who has a MSI645 ultra reports the temp monitor as being broken. Yours is too.

No you misunderstood me. I know the software is wrong and all that. But about your computer not booting when you unplugged the fan. I heard that you have to have a fan plugged into that plug on the motherboard. You know the cpu 3pin plug. I heard that from somewhere, but I'm not sure if that was on the AMD motherboards or Intel. That's all I'm saying. As far as the temps, I get the same temps as you do. 49ºC in MSI PC Health and MBM at idle and no higher than 51ºC under load. But yet the bios says 34-36ºC. And while your in the bios, it is suppose to thave the CPU under a load. My system temp is 24ºC and room temp is about 22ºC. Oh well, other than that, the board is pretty good, cept for I don't like not having more selections for VCore voltage. I would like to get at least 1.8 so I could clock my 2GHz Northy to around 120+ fsb. 112-113MHz is as high as I can go at 1.6volts Well really 1.56.

My description wasn't quite celar enough I guess -- the system keeps crashing only after the temp goes up to 42 in the bios. Never mind about the fan -- point I was making is that 42 C is just too low a temp for any system to be crashing. Therefore the BISO temp is also wrong.

I think I have seen a voltage mod/hack to increase Vcore on these mobos. Let you know If/when I find it.

Oh ok, I over looked your 42ºC temp in Bios. Hmm, I just did mine and it booted right up. The temp was between 42-44ºC without my fan plugged in. But yeah, if you find the volt mod on this board please post it. Thanks.

yup i got the same problem its either 49 or 50...ugh and bios shows 30c...go figure...

What Bios version do you have....
Did you flash the latest bios to fix some of this temp sensing problem.
It fixed some but it doesn't seem right. Mine says that I run 55 when OC to 2.4. Unfortunetly I made the Vmod and now I am running about 5 C hotter at the same speed.

whats the newest version of the bios?

hi,i have a msi 645 ultra.the newest bios is 1.6,plus they have new software updates too..the temp reads lower in the bio's,than on the mb monitor in windows..

they have a new fuzzy3d its called now,i think.plus other software updates.the problem is the sensor..and whats more troulbeing is no one from tech support responds in the fourms..and thats real sad..im not buying another msi board for sure,it works ok other wise.

with my 1.6a i hit 2450mhz,thats about it,with out doing a cpu wire trick.it still is pretty fast..

there tech support least in the forums is non exsistance...

they won't admit the sensor is bad...my 2 cents..hehe

heres the new fuzzy3d,which supports

-- Support Tualatin CPUs.
-- Add Adjust Vcore & AGP ratio.
-- Support new main board: MS-6398E, MS-6567, MS-6566E, MS-6580
AP version: 3.3.61.0

heres the link to there page

http://www.msi.com.tw/support/software/main.htm