What happens when a CPU reaches its Tcase temps?

[shanmu54321]

Basically, I scrapped out a pentium 820, Intel LGA 775 mobo from my attic. I ran it with the stock cooler, and within 30 secs the computer shut down automatically. After researching in the bios, i found out that the cpu ran at 98*C. I bought a deepcool cooler and installed it. Now it runs around 75*c. Now it doesn't shut down. I have heard many people saying that at Tcase temperature, the computer would shut down automatically. If that is true , the temperature sensor on the motherboard is malfunctioning since the computer would shut down around 98*c  because the Tcase for my CPU is 64*c. Is it true that at Tcase temps, the computer would shut down?

[Master Disaster]

I think you mean Tjunction?

Tjunction is the temperature at which the system shuts off to prevent damage to the cpu.

Also something is very wrong if your Pentium is running at 80°c+ with an aftermarket cooling solution.

I'd expect no more than 50°c as an absolute maximum, even for an older 775 cpu.

[Naeaes]

Yeah. Processors with Speedstep available, just drop their speed to relive the heat but Pentium D doesn't have that. So it just shuts down. There are a bunch of sensors in it though. The tCASE is measured at the integrated heat spreader but there are sensors in the cores too. The cores get hotter than the IHS. Maybe you're looking at the wrong one? Anyway, it's not on the motherboard, it's in the CPU. But you're right, it can malfunction, the BIOS might be reading it wrong and so on and so on.

[gonvres]

I often wonder if they genuinely do shut down. I got a system built by a local computer shop once, it had an aftermarket CPU cooler, but they didn't add any thermal paste. I was a bit of a newb at the time and didn't really install any temp monitoring software, anyway it ran very hot for years on end and never once shut down. When I finally installed hwmonitor after using it for multiple years it was saying the cores were hitting 100+ under load. This was a first gen i5 CPU. 

 

Never once shut down.

[Naeaes]

I think you mean Tjunction?

Tjunction is the temperature at which the system shuts off to prevent damage to the cpu.

Also something is very wrong if your Pentium is running at 80°c+ with an aftermarket cooling solution.

I'd expect no more than 50°c as an absolute maximum, even for an older 775 cpu.

Tjunction is measured inside the cores and averaged between all of them. Tcase is measured at the IHS with a single sensor. Basically the same thing but with a twist. Anyway, the sensors can definitely be calibrated all to hell right from the start or just 'wear down' over time. 

[Naeaes]

I often wonder if they genuinely do shut down. I got a system built by a local computer shop once, it had an aftermarket CPU cooler, but they didn't add any thermal paste. I was a bit of a newb at the time and didn't really install any temp monitoring software, anyway it ran very hot for years on end and never once shut down. When I finally installed hwmonitor after using it for multiple years it was saying the cores were hitting 100+ under load. This was a first gen i5 CPU. 

 

Never once shut down.

You may have won in the sIlicon lottery. Basically, the CPUs (and anything made with silicon transistors) are individuals and different from each other. Some units are good, some are bad, most are average and a tiny percentage are friggin' awesome. The values they advertise fall in the average category but it by no means is to say that some of them don't run above it all like a dream. Did you ever try overclocking it?

[agent_x007]

Well... it switched off because Pentium D 820 doesn't HAVE a core sensors... or, well.. any technology to drop it's Vcore/Frequency, within the level needed to keep PC "alive" at ~100C (CPU Temp). 
Minimum multi is x14 (with 800MHz FSB that gives 2,8GHz) and Vcore dropping isn't supported (90nm technology for U ).

Next thing that CPU can do (to not die), is to switch off.

Lastly : Tcase max. and "Shut Down" temps, are NOT the same.

MB will read data from it's IHS/analog sensor and, based on it, will make a decision to turn off (in some BIOS'es, U can change the setting at which MB will switch off PC).
Tcase is for CPU cooling manufacturers (Intel's way of saying how cool the CPU should be, where this temp is measured, during maximum load).

Smithfiled (aka. 2x Prescott), WILL burn like Chernobyl if left unchecked.
Basicly : It needs a REALLY good cooler (U can forget about running it on that low profile cooler from 45nm PDC's/C2D's, even new, the "stock" high profile one in moderate air flow case, can berally able to hold it under 80C at max load).
U can get temps down by droping CPU Vcore by 0,05V - 0,1V (more than 0,1V only if needed, since U increase risk of losing stability the further U drop Vcore).

PS. Don't forget to check push-pins on CPU cooler (they are quite easy to break and can be hard to lock in place).