Dell Precision 7540 and 7740 Owner's Thread

If downclocking remains as a feature, then it makes absolutely no sense whatsoever, from an engineering standpoint, to prohibit undervolting. Is there a way to take this matter up with Dell somehow???

 

No, the systems can typically maintain boost speeds in the 3 GHz range with either CPU. The "rated speed" doesn't mean much.

The systems are constantly changing the CPU speed based on load. What I describe is just putting a cap on how high the speed is allowed to go.

 

Nice finding! Worked for me as well.

Did you try a reset to defaults to get undervolting back, when you had 1.8.2 installed?

 

Those are the clock speeds at 45 W; rest assured the 7740 can handle well beyond that. That said, given a certain power limit, the lower-core-count part (2276M) will perform better than the higher-core-count part, because each core gets a larger percentage of the power budget. Once again, this is all theory, and actual use differs wildly.

@Aaron44126, on Plundervolt: only a matter of time before the 7X30s get such a BIOS update, too. Pity, though, because Dell was supposed to fix several other issues, too...

 

If you disable SGX in the bios does undervolting work again? Based on reading about the security advisory if you are not using SGX then undervolting should not be a security risk, correct?

 

It is true that if you do not use SGX, then this vulnerability does not apply. (I do not know if disabling it will restore undervolting functionality.)

However, SGX has started to be used in consumer applications, specifically with regards to video DRM. I believe that it is required in order to stream Netflix in 4K, for example.

 

So with these CPUs running at 3 GHz, is it possible that the E2276M would actually consume less power than the E2286M (because it has fewer cores) ??
In other words, is it possible to interpret the 45 W TPD as the power the respective CPU consumes at the respective clock speed??

 

E2276M would consume less power than the E2286M (if both were running an all-core load at the same clock speed), yes.
You could say the "rated speed" is the speed at which the CPUs run at 45W (as @Ionising_Radiation mentioned above). Still a bit fudgy, since the power usage depends not only on the clock speed, but what type of load is running on the CPU.

 

Oh, thanks for the info! I guess that now that I think about it, the microcode fix is probably not something that can easily be enabled or disabled. So likely no more undervolting on these new bios's at all.

I am guessing for the most part this isn't a big deal for people using Precision's or Latitude's. I have never come across a single other person through consulting or business contacts that bothered to undervolt their business laptop. One of my IT friends does know about Throttlestop / XTU but they can't really put it on their company's approved app list without justification and a bunch of documentation explaining use.

 

What I've done:
upgrade to 1.8.2 (cannot undervolt)
downgrade to 1.7.0 and reset to factory default (can undervolt again)
upgrade to 1.8.2 and do nothing else (voltage offset still in effect as reported by ThrottleStop)
SGX remains "software controlled" in BIOS.

Reference: post on r/Dell