Xeon Phi 31s1p Cooling and Motherboards

OK, you got one of the Intel “fire sale / crazy Eddie sale” Xeon Phi 31s1p cards … now what?

First if you managed to get one congratulations! That’s a nice card, it’s like a 3120p with more memory or a 5110p with 3 fewer cores … and you basically got it for a 90% discount! However, now you will probably want to make it work.

What you need:

  • A way to power and cool it (this is a passive card that will idle around 70W and hit close to 300W under load. If you don’t have air moving through it you will see it’s magic smoke escape)
  • A motherboard to put it on
  • The Intel compilers to write some code for it
  • Linux experience so you can install it and understand how it works

NOTE! The following version of the Peak Mini is no longer available. We have a new better design for the Mini but can only use active cooled cards. For passive cooled cards like the Phi 31s1p and 5110p we have a nice cooling package for either the single or dual Peak Tower. –dbk


We can do it for you. We’re working up a Peak Mini with a 3D printed fan duct. You will be able to order the system, send us your card, and we’ll install it in the Mini, load up CentOS with a Phi configuration, the Intel 2015 compilers and do some testing and send it back to you … we do have a few of the 31s1p cards left in case you haven't gotten one yet. We also have a nice 2U chassis for passive cooled cards …


Motherboards for Phi:

Two things you want in a motherboard for your Phi;

An X16/X16 PCIe slot (you can run it with X16/X8 but your memory bandwidth will suffer somewhat, which may or may not matter to you) This is obvious so enough said.

The second thing you NEED is a motherboard with 64-bit BAR support. This is essential! Even though this has been in the PCI spec for some time it is still not common to see “large BARs” supported on boards other than those for dual Xeon’s. You have to verify that the board your are thinking about using has this support. Supermicro has the most consistent implementation. I believe all of their modern Xeon boards have support. Most dual Xeon will have support but you have to check.

How to check if a motherboard will work with Phi;

The easiest thing to do is go to the motherboard vendor web site look up the board and download a copy of the manual and search for the phrase,

“Above 4G Decoding”

If you find that phrase then there is a good chance that you will be able to get your Phi to work on that board. (It’s not guaranteed! It doesn’t hurt to actually check with the manufacturer to confirm they have tested Phi on their board.) [ Note: We often have a custom BIOS done for our systems so, just because we use a particular board doesn’t mean it will work for you! ]

Power and cooling:

You should be able to accommodate an additional 300Watts of power draw on any system that you add a Phi too. You will also need an 8 pin + 6 pin PCIe power connector from your power supply. This also means you have to be able to remove around 300Watts worth of extra heat from your system and the “p” in 31s1p stands for “passive cooling”!

Cooling the card can be the biggest challenge. If you have a rack mount chassis (or a rack mount chassis on it’s side that looks like a workstation 🙂 with special fan mounts to accommodate high wattage passive heatsink cards then you are good to go. If you are going to try to put the 31s1p in a “regular” workstation then you will need to do some modifications to get enough air moving through the card to keep from burning it up. (it does have good thermal protection and will shut down before it smokes).

The key is getting enough pressure to force air through the heatsink.

If you are doing an ad-hoc cooling solution then the easiest thing to try is attaching a high speed high pressure 80mm fan to the back of the chassis over the PCI slots that the card is occupying. This will pull air through the card and may be enough to work with as long as you have good air volume going into the interior of the case. If it doesn’t quite give enough cooling then you will need to try to mount an internal fan near the air inlets on the Phi to get a push-pull airflow going.

One sad note: to get enough air going through the card you are going to have to live with some fan noise. The guys here at Puget Systems hate that and we try to make it quiet, however air cooling the 31s1p is going to be noisy!

Intel compilers:

The Xeon Phi is very much an Intel device! You are really going to need a recent Intel Parallel Studio installed to do any development work on the card. These compilers are excellent so this is not such a bad thing. However, they are not free! If you don’t have a license already then check with the vendor that you got your card from, you may be able to get an extended (6 month) trial license. If you are not getting paid in any way for what you are doing with the card then you may qualify for a free non-commercial license. Note that academic is NOT “non-commercial”!


The Xeon Phi is a very interesting but you have to keep in mind that it is a Linux device, period! It runs an embedded Linux OS, so even if you are trying to work with the card under Windows you will have to know some Linux to use the card. You can think of it as an extra Linux machine running on your system. It will really help if you have a little Linux system administration experience. Don’t let that stop you from trying to use it plugged into a Windows system, it does work under windows! (but I don’t recommend it). Just be sure you keep the right perspective about what you are doing.

The Xeon Phi is very interesting device but it is very much a developers device at this point. You are going to have to roll up your sleeves and work with some code! Even if you don’t have much luck with the card you will definitely learn about optimizing code for modern many-core architectures and wonderful stuff like vector units … everything you do with the Phi will give you better insight into program performance optimization and that will translate right back to your Xeon CPU’s too.

Best of luck!

Happy computing! –dbk