Erratum HSD147: Unpredictable Operation at Turbo Frequencies Above 4.0 GHz

[Ikaruga]

Hi,

I wonder if anyone knows anything "more" about this erratum. It only affects a single processor, the 4790K and nothing else. The spec update docs says there is a possible fix with a bios update, but I'm still very curious what could it be which doesn't affects any other Haswell CPU, not even the 4690k.

Problem: Machine check errors, system hangs or other unpredictable system behavior may occur when operating at turbo frequencies above 4.0 GHz.
Implication: The processor may signal machine check errors, hang, or exhibit other unpredictable system behavior.​

btw, that list is scary :]

 

[Kursah]

The 4790k turbo's over 4.0GHz, to 4.4GhzHz. The next fastest ones are the 4770k and 4690k, which are 3.5/3.9Ghz standard and turbo clocks. So what I gather is that what that document is referring to is that there may be a stop error or other type of unpredictable error because the system is not expecting a processor clock that fast. iirc the 4790k is one of Intel's fastest consumer CPU's atm.

Can't say I have or know anyone that's had anything related to this error, I wouldn't be too worried. Maybe it's Intel covering their ass for unstable CPU's... if it was fixed with a BIOS update then great.

It would be scary if there was more about this problem than this one thread. I have two 4790k's in Z87 boards and just sold my 4770k and z87 board...all worked great at stock and faster than stock.

 

[newtekie1]

I'm just guessing, but I think this might be related to the cache. Since the cache, by default, clocks up to the same speed as the processor it runs at 4.4GHz when the processor is boosting. In my experience with my 4790K, to get any kind of stability when overclocking my processor I have to set the cache multiplier to 40 to limit the cache to 4.0GHz.

 

[Ikaruga]

The 4790k turbo's over 4.0GHz, to 4.4GhzHz. The next fastest ones are the 4770k and 4690k, which are 3.5/3.9Ghz standard and turbo clocks. So what I gather is that what that document is referring to is that there may be a stop error or other type of unpredictable error because the system is not expecting a processor clock that fast. iirc the 4790k is one of Intel's fastest consumer CPU's atm.

Can't say I have or know anyone that's had anything related to this error, I wouldn't be too worried. Maybe it's Intel covering their ass for unstable CPU's... if it was fixed with a BIOS update then great.

It would be scary if there was more about this problem than this one thread. I have two 4790k's in Z87 boards and just sold my 4770k and z87 board...all worked great at stock and faster than stock.

I know there is not much we heard or know about it, I was not worried, curious what could it be.

I was thinking about what you proposed, but wouldn't that also happen if you would OC the 4770K over 4Ghz? After all, that one is an unlocked CPU too, or they only acknowledge errata for stock voltage/speeds?

 

[Kursah]

I considered that same thought and never ran into any issue with any 4xxxK series overclocking beyond 4.0Ghz. But from a stock point-of-view that's the only aspect that made sense..I suppose cache speed as @newtekie1 would make sense as well though, could definitely have been an issue there.

 

[Ikaruga]

I'm just guessing, but I think this might be related to the cache. Since the cache, by default, clocks up to the same speed as the processor it runs at 4.4GHz when the processor is boosting. In my experience with my 4790K, to get any kind of stability when overclocking my processor I have to set the cache multiplier to 40 to limit the cache to 4.0GHz.

That could be it indeed, thanks!

 

[newtekie1]

Another thing that I just thought of that leads me to believe this might be a cache issue is the fact that they say it can be fixed via a simple BIOS update. It would be likely that BIOS update simply made it so the default behavior is if the processor boosts to over 4.0GHz, the cache won't go higher than 4.0GHz.