After having somewhat recently acquired two servers, I have been spending some time both setting up a useable home network setup. Part of this was to also take a look at power consumption, as rack servers aren't generally known to be very power efficient, which can be a bit of an issue for your power bill if you're doing some kind of home lab type thing.
I have two near-identical Intel branded servers, with some minor variations between. One has a pair of Intel Xeon X5570 quad core CPUs, clocked at 2.93Ghz and with 8Mb cache. The other have the slightly lower specced Intel Xeon X5550 quad core CPUs, clocked at 2.66Ghz. Both are rated for 95 watts TDP, meaning they're quite the power hungry buggers.
Not too long ago I stumbled upon a data sheet listing out CPUs of this era, along with their power consumption. I noticed the L5640 a they seem to be the right mixture of providing enough power whilst at the same time consumping less, having a TDP listed at 60 watts. With two dual-CPU servers this could bring quite a noticeable difference in energy consumption, so I was curious to give it a try. I found a local seller who had 25 of these at a decent price, so ordered 4.
Swapping the CPUs
Replacing the CPUs was, as you might expect, quite straight-forward. I'm pretty sure the most challenging part was to pull the server out from my "stack," for lack of a better word, as I have yet to stumble upon a small yet affordable rack.
After opening up the case, I loosened all four screws of the first heat sink, after which it simply lifts off. I immediately cleaned off the old thermal paste as that stuff really does get everywhere if you don't. After this it's as simple as plopping down the new CPU, applying some new thermal paste (don't go overboard; a little bit goes a long way). I used some Arctic Blue as I still had it from a previous project. After this you can screw the heat sink on again, and you're all set. Be sure to put it on the right way, follow the path the air takes through your server.
At first boot, your server might complain and throw some beeps. This is to be expected, as it's simply noticing stuff has changed. It'll be good to double check everything looks alright in the BIOS, but that's about it. Unless you're running a particularly picky operating system (ie. Windows), everything else should just work fine.
So, how do they perform?
While the L5640 is a generation newer, it is a lower powered version, so differences should exist. I was curious to see how they compare, so ran a Geekbench test both before and after the CPU swap. The results were both interesting and not all that surprising. Across the board they're basically very comparable, if not almost identical. This is good, as it means you're getting about the same while at the same time they consum less power.
First, here are some of the key specifications of these CPUs:
|# of Cores||4||4||6|
|# of Threads||8||8||12|
|TDP||95 Watts||95 Watts||60 Watts|
Geekbench' single core results are, as can be expected, in favor of the more powerful X5570, with a score of 2575. The L5640 came in with 2019 points.
Multi-core scores are more favorable to the L5640, giving them a total score of 16,134, compared to the X5570's 14,737.
For a point of comparison, I also ran the same tests on both a 2015 12" MacBook running an Intel Core M-5751 at 1.2Ghz, as-well as my Hackintosh (a topic for another article) running an Intel Core i5-3570 at 3.39Ghz. While the specific use-cases of each machine is, of course, different, I thought it might help put things in perspective.
|Cores||Speed||Single-core Score||Multi-core Score|
|Dengdengi w/ X5570||8||2.9Ghz||2575||14737|
|Dengdengi w/ L5640||12||2.26Ghz||2019||16134|
|12" MacBook (Early 2015)||2||1.2Ghz||3033||5658|
|Core i5-3570 Hack||4||3.39Ghz||3872||11450|
For a full comparison between the two CPUs I recommend you check out the Geekbench results for both my tests. You'll notice that with the exception of the AES test, both CPUs perform very similarly.
What started all of this was, of course, power consumption. Between four CPUs, a saving up to 140 Watts ought to be noticeable. I have a basic, decidedly consumer grade wattage meter, so while the results are by no means accurate, I did notice an immediate decrease in power usage. Whereas this particular server would normally idle at around 170-180 Watts, it now sits comfortably around 130 Watts or so. An expected but still very much welcome improvement, I would say.
I haven't yet had a chance to switch out CPUs in the other server, but when I do I'll be sure to update this article with numbers for the X5550 CPUs as-well.