Alright, put your thinking hats on because this one's interesting (and a bit long, sorry).
I just returned from college last week and recently noticed that whenever my GPU is under a significant load, my wireless PCI card basically stops functioning
. Before I went off to college, everything was working fine (only change to hardware was the addition of the Samsung 840 Pro, physical location of PC and router is exactly the same), and I didn't notice the problem at college because I was using wired ethernet.Hardware details to start (most relevant components bolded):
ASRock X58 Extreme
Intel Core i7-920 Bloomfield @ 3.2Ghz
ARCTIC COOLING Freezer 7 Pro Rev.2EVGA GeForce GTX 680 @ +110/+220
A-DATA Gaming Series 12GB DDR3 1600G
Samsung 840 Pro 256GB SSD (OS drive)
OCZ Vertex 2 120GB SSD (Games & Data)
WD Caviar Blue 640GBCorsair TX750W power supply
Windows 7 Home Premium 64-bitD-Link WDA 2320 PCI Rangebooster G Desktop Adapter
To confirm the problem I ran the Heaven Unigine Benchmark 4.0 on the Extreme preset while having inSSIDer
open and pinging google.com in a command prompt for the duration of the test. Here are the results:
As you can see from the screenshots, as soon as the test starts the ping requests to Google start failing, and inSSIDer shows a complete loss of signal. Note that the inSSIDer graph isn't an indicator of connection
strength, it's an indicator of signal
strength - even if you're not connected to a given network the graph will still show the received signal strength for that network. The fact that the RSSI
indicator drops off completely means that not only is the active connection to the network lost, but the adapter can't see the router's signal at all
. This clearly indicates it's a hardware problem and not a software one.
I've eliminated processor load (or general loading of the PSU) as the cause by running Prime95 at full load for a good several minutes - connection strength as reported by inSSIDer stayed constant and there was no significant change in ping times.
I've Googled around looking for this type of problem and have only found two other cases: A Tom's Hardware forum thread from last year (here
) and an ancient thread from 2007, which is notable because he has the same wireless PCI card that I do (here
). Neither of these found a solid cause or solution to the problem.
It seems to me there are 3 possible causes to this:
(1) Heat from the 680 is affecting the WDA 2320 and pushing it out of it's operating temperature range
, causing it to lose signal. This seems pretty unlikely to me, given that the cards are separated by 2 slots, my case is pretty well ventilated, GPU temps are pretty normal, and the problem never manifested itself a year ago with the same combination of hardware.(2) The 680 under load is drawing too much power, starving the wireless PCI card of power
and causing it to stop functioning. Also seems unlikely, given that I haven't seen any other problems with the PC lately, my power supply is of good quality, and placing other components of the system under load doesn't seem to affect anything. And a year ago, I wasn't having any power problems - the only hardware addition between now and the last time everything was working was a Samsung 840 Pro SSD, and SSD's don't exactly draw tons of power (I although I guess it could be theoretically possible that it was a "tipping point" for the limit of the PSU).(3) EMI interference from the GPU is spitting noise all over the WiFi frequency range, causing the adapter to drop signal.
Honestly this seems least likely at first but it's what I'm most concerned about. If I run a test to put the GPU under load and hold my Galaxy Nexus up to the back of the PC (near the antenna of the PCI adapter), guess what? The wireless connection on the phone drops.
This seems to be pretty damning evidence that there is indeed some sort of strong EMI from the 680.
Theoretically, though, this may actually make sense. My wireless router is on channel 1 in the 2.4 Ghz spectrum, which is 20 Mhz wide channel centered on precisely 2412 Mhz
. Guess what? With my current overclock, my 680 core boosts to 1201 MHz under load. The second harmonic
of this frequency is 2402 Mhz
, which is very, very close
to that 2412 Mhz of the 2.4 Ghz Channel 1 spectrum.
It's also worth noting that before I went to college, we had a different wireless router (Linksys WRT54GS) than we do now (Apple Airport Extreme 5th gen), which I believe
was on channel 11, while the current router is on channel 1 (due to lots of other networks on channels 6 and 11 in our area). Perhaps this small (~72 MHz) difference in frequency was enough to be the difference between interfering and not interfering.
I'm going to run a few more tests to try to confirm this (like resetting my overclock and changing the channel of the router), but it's impossible to confirm without a WiFi spectrum analyzer like this
, and I'm not about to go out and spend $200 on hardware that I'm probably only going to use once.
So it seems like my GTX 680 is spitting out enough EMI to completely block out the wifi signal from my router with noise. I guess I'm asking: is this a problem? Should I be concerned? If the EMI is powerful enough to completely **** up my wireless adapter, how do I know it's not spilling all sorts of other EMI in other frequencies all over the rest of my delicate hardware?
And does anyone have any other ideas about what may be causing this issue?
Thanks in advance, sorry for the length!