Gigabyte GA H87-HD3 System Fan Issue?

[fallenangle]

Just powered up my first completed build with the GA H87-HD3 MB.

Everything working, HDD idling, all fans going, GPU fine etc, pretty pleased. Went through the BIOS menus seeing what's what and all looked good except I noted that under "PC Health" only the CPU fans and System Fan 3 (the rear exhaust) were reporting RPM info.

System fans 1 and 2, set to the default Normal ie. PWM control like the others, are both pairs of Akasa Vipers (2 x 120mm/2 x 140mm). They're connected to the MB by Akasa PWM Y splitters and both pairs are spinning, just not reporting RPM status.

I tried them on Silent and Manual (x1.0) modes and they changed speed fine so they're apparently working correctly but still no RPM report. However when Full Speed is selected immediately the RPM for both appears.

Obviously I've tested the connections and I've also disconnected one of each of the pairs and re-tested with the same results. About the only thing I haven't done is remove the Y splitters and tested each of the fans plugged directly into the MB headers.

If this were a particular problem with the Akasa Y splitter why is the Full Speed RPM being reported and why isn't it affecting the two CPU Akasa Viper fans which are also connected through another Akasa Y splitter to their header?

Questions:-

Is this something that is likely to be fixed after installing the OS and then the MB drivers? It just seems a bit unlikely that would fix it since the other fans are reporting RPM OK straight out of the box.

Is there any cause for concern? It does appear to be a specific reporting issue only, otherwise the fans seem to be working as intended.

What I don't want to discover later is that there are some known problems with the 1 and 2 sytem fan headers with this MB and have to dismantle the whole thing to get it sorted. I've searched online and can find no similar recorded issues so that's why I've come here for advice.

 

[fallenangle]

I've tracked down the culprits and it is 'just' a reporting issue but it actually raises more questions than answers.

All fans are functioning mechanically 100% perfectly the problem lies with the RPM reporting from two particular Akasa Viper 120mm fans, apparently identical to the three others I've used in the build with no such problem.

The two misreporting ones behave identically and mysteriously also identically to a Scythe 120mm PWM fan I also tested. All the bog standard 3 pin fans (Coolermaster, Corsair) I tested have no similar issue and neither does the 120mm PWM Coolermaster fan that came with my Hyper 212 Evo Cooler.

None of the misreporting ones show RPM readings in Normal, Silent, Manual PWM (default settings) modes on any of the three system fan headers.

All show RPM correctly at Full Speed, all headers.

All report RPM correctly at the highest Manual PWN mode, all headers.

Connected to the SF1 header no other Manual PWM setting provided any RPM details.

Connected to the SF2 and SF3 headers all these fans reported the RPM in Manual PWM mode with any setting 2 and above.

The only anomaly is that occasionally one of these fans, particularly the test Scythe, would report grossly exaggerated RPM in Normal mode but this would usually show 0 again on reset.

It appears to be a specific reporting problem between these particular fans and the MB. But surely this can't be coincidence. Three fans, one of a different make, which in identical fashion do not report the RPM correctly in three out of four modes but all have no trouble doing so at Full Speed. Seems very unlikely to me.

Any ideas/comments welcome.

 

[fallenangle]

I've done a bit more testing and research and I think I may have an explanation. It looks like it could be either a design fault or a more general fault with the particular fans rather than the MB.

http://forum.corsair.com/forums/showthread.php?t=119379

The above thread does seem to suggest it maybe a design or component/build spec issue with particular fans rather than a manufacturing fault.

The theory is that the resistance on the fan speed tachometer wire is too high reducing the signal below the point the MB recognises it.

It does fit in with facts: only in the High Speed and higher speed settings Manual PWM modes is RPM being reported ie. the signal becomes strong enough to over come the resistance. It also suggests that in Normal mode RPM reporting may start as the fan speeds up when the system is under load.

I suppose the receiving pin/channel on the MB could still be involved as evidenced by the occasional reporting of (grossly incorrect) RPM speed in Normal mode on the System Fan 2 header with some of these fans. But I think it much more likely the fans are entirely where the problem lies.

That is good news as regards my fears it was a MB problem but damned annoying because othewise the fans work perfectly. However if I want matching Akasa fans which do not have this reporting issue I have to buy two new ones and take the gamble that they don't exhibit the same problem.