Enabling link power management, etc, in BIOS?

Notice: Page may contain affiliate links for which we may earn a small commission through services like Amazon Affiliates or Skimlinks.

larrysb

Active Member
Nov 7, 2018
108
49
28
I'm running Xeon E5-V4 processors on a few Asus X99 WS and X99E WS motherboards. There are lots and lots of options in the bios for various link and other power management features which are disabled by default. I do see that many of these are enabled on brand-name pre-built workstations and servers as default settings.

SATA ALPM - any reason not to enable aggressive link power management?

SA SMI ASPM?

PEG ASPM?

PCH DMI ASPM?

ASPM support? (various on board devices)

Asus branded "EPU" powersavings?

I know it doesn't save the whales or anything, but no point in burning power on a machine that has a fair amount of idle time doing not a lot in the home lab.
 

EffrafaxOfWug

Radioactive Member
Feb 12, 2015
1,394
511
113
It's usually a question of whether the devices hooked up to the board properly support the various levels of power management TBH. Pre-built workstations have the maker testing their various peripherals and see what works and what doesn't, if you're doing a BYO it's basically up to you to do the same testings.

In some cases, turning on power-saving settings can both save negligible amounts of power and yet still cause intermittent and hard to diagnose issues. One I remember very well was all sorts of SSD oddities when SATA ALPM was turned on for certain SSDs - drives dropping off the bus, failing to resume from sleep etc. Thankfully power saving is a big thing these days so turning on these settings should be much less riskier than it used to be, just beware of odd behaviour down the line.
 

larrysb

Active Member
Nov 7, 2018
108
49
28
Yeah, that's the part that's kind of weird - the options are not always labelled the same names as found in the Intel chipset docs (if you can even access them as an ordinary person). No real indication in the BIOS manual what they're really doing.

Even ASUS's own "EPU" option doesn't even explain what it might actually do.

Since the machine is on a lot of hours, even small savings help reduce power consumption and heat build up in the room.

Of course, it seems most pre-built workstation class computers that have these options on, are often very loud and not real suitable for home labs either.
 

EffrafaxOfWug

Radioactive Member
Feb 12, 2015
1,394
511
113
Yup, it can vary greatly between vendors both from what various other vendors and standards organisations might call things, along with the marketing guys throwing things in to the same blender. Generally the only way you'll get detailed info on exactly what some of the less-common acronyms entail IME is technical support tickets or finding a lucky thread or patch notes on LKML.

That aside, when I've been trying these things out in the past I generally turn on one option at a time, run the system for a week observing power consumption and performance and other stuff, and as long as nothing odd happens enable the next option in a week or a month or so.

I'm probably sounding like I'm over-complicating this - chances are you can flip on every power-saving option in the BIOS and have no stability issues at all, but at the very least it's a good idea to only change one thing at a time and keep a log of it. That way it's easier to undo your last change, or re-do the same changes if you've flashed your BIOS and erased your changes for example.

P.S. The Asus EPU, if I remember correctly, was back from the C2D days back when power-savings were starting to become trendy, there were a bunch of other similarly named initiatives for power-saving secret sauce from the other mobo makers as well.