Quanta LB6M (10GbE) -- Discussion

TheBloke

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I'm going to re-write my previous post as it was a mess of updates and edits:

I have done a quiet(er) fan swap on my LB6M, running Brocade firmware. I got 3 x Noctua 40mm x 20mm 3-pin fans for the main switch. I wanted 4-pin PWMs but they were out of stock for a few days, so in my impatience I got 3-pin thinking they'd be fine. How annoying; they're not.

The core problem is this: most of the time (but not all) with 3 x 3-pin fans connected, show chass gives me no temperature information, and always shows all fans as OK:
Code:
Fan 1 ok, speed (manual): 1<->[[2]]<->3
Fan 2 ok, speed (manual): 1<->[[2]]<->3
Fan 3 ok, speed (manual): 1<->[[2]]<->3
Fan controlled temperature: 0.0 deg-C
...
Exhaust Side Temperature Readings:
        Current temperature : 0.0 deg-C
        Warning level.......: 80.0 deg-C
        Shutdown level......: 90.0 deg-C
Intake Side Temperature Readings:
        Current temperature : 0.0 deg-C
EDIT: as per next post, this is not specific to me, or Brocade. I've found an old post where another guy had the same problem when using 3-pin fans, according to his "show environment" output on FastPath, which showed Temp = 0 Celsius. And further, my testing has confirmed that manipulating the fourth pin does weird things to the temp monitoring of show chass.

If I plug in 3 x 4-pin PWM fans, show chass immediately works as normal. Tested both with the original 3 x 40mm fans, and also three Noctua 4-pin PWM fans. When 3 x 4-pin fans are connected, I get working temperatures and working fan detection.

But what is very strange is that the first time I connected my 3 x 3-pin fans, I got working temps, and over multiple power cycles. I connected the three fans, I booted, I checked show chass, it had temperatures as normal. I then power cycled several times while changing the PSU fans, and every time I booted I checked show chass and it was always working fine.

Once everything was setup, I let the switch idle for about an hour, monitoring the temperature. I then decided I would test temperatures at a lower fan speed, using the Noctua low-noise cables. I swapped all three Noctua fans out with their Low Noise Adapter (LNA), and power cycled.

This is when the problem started - after that boot, and most every subsequent boot, I got no temps in show chass. And if I disconnect a fan, it still shows as "Fan OK".

Since then I have tried the following without change:
  • Fiddling with wires/checking connections etc
  • Power cycling five, six, seven times in a row, with gaps in between
  • Pulling and re-plugging the fan tray
  • Unplugging each of the three Noctua fans in turn, to the point of having 0 fans connected
  • Booting with 1 x original fan + 2 x Noctua
  • Booting with 2 x original fan and 1 x Noctua
  • Booting with 1 x original fan or 2 x original fan - which is really weird, because this is a standard failure case! (EDIT: Ah, it depends which fan is connected. If the one nearest the PSU is connected - fan 3 - I get temp figures and that one fan behaves normally; if it's not, then any connected fans run at 100% speed and no temp figures are shown.)
  • Putting in the fan tray from my LB4M, which is the same model number, and trying the 3 x 3-pin Noctua fans in that instead.
However, some things did work, briefly:
  • As mentioned, having 3 x 4-pin PWM fans always seems to work
  • 3 x 3-pin worked when I first put them in, and continued to through a couple of power cycles
  • After that, I twice got it working again by:
    • Running with 1 x original + 2 x Noctua, booting = not working
    • Replacing the 1 x original with the third Noctua and booting again = then it worked.. but only to the next power cycle
    • This sequence worked twice in a row, but then the third and subsequent time I tried it, it stopped working.
I am really at a loss as to what is happening here. I thought the 4th pin was purely an output?

Then there's the question of why it worked perfectly the first time I connected everything up, and for at least an hour afterwards, and then almost never worked again after I first connected the 3 x LNA cables. But then did work twice more, very briefly, after I swapped 1 x original fan for a Noctua.

Maybe there's a way to connect the fourth pin to something, to 'fool' the motherboard, given it seems to be really affected by not having something on that pin?

Thanks in advance.
 
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TheBloke

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Doh, it looks like this is not specific to me, and must be a HW issue. I just searched through the whole thread, and found this:

So I swapped out the 3 fans today.
....
New Fans
Sunon 40x40x20mm 3 pin fan #KDE1204PKVX
....
(FASTPATH Routing) #show environment

Temp (Celsius)................................. 0
It probably wasn't as obvious on FastPath, but it's clearly also showing 0 Celsius for that guy when 3-pin fans are used.

So I still don't understand why/how I got temp monitoring working on several boots when using three-pin fans.

I also don't understand how the lack of a connected 4th pin can mess up temp sensing. Maybe some low level issue? It's expecting a connection on that pin and that causes a HW bug?

Could I connect that pin to.. something? I don't really know how fans work. I know it's a PWM signal pin, so I suppose it sends a fluctuating voltage down it that controls the motor? I could put a high value resistor between it and ground? I don't want to risk damaging anything..

UPDATE: Ha! Yes that fourth pin sure is relevant. I got out my multimeter and, with the switch running and (Noctua 3-pin) fans operational, I (carefully!) probed the pins on one of the fan connectors:
  • Between pins 1 & 2 (Black and red / Ground & 12V): +12V, of course
  • Between pins 1 & 3 (Ground / Tach): Around 3 volts, slightly fluctuating
  • Between pins 1 & 4 (Ground / PWM): Around 0.5 volts, slightly fluctuating
Then I went back to show chass, planning to change the fan speed from 3 to down to 1, to see the effect on the PWM voltage. First thing I see:
Code:
Exhaust Side Temperature Readings:
        Current temperature : 128.0 deg-C
        Warning level.......: 80.0 deg-C
        Shutdown level......: 90.0 deg-C
Intake Side Temperature Readings:
        Current temperature : 128.0 deg-C
Hmm! Well that sure did something :) What the hell is it using this fourth pin for, and why is it even connected to temp monitoring? Are they somehow monitoring temp from the fourth pin?

Also notable is that 128 is well above the shutdown level, but of course it did not shutdown. So maybe shutdown is controlled using a separate temp sensor in the chip. Or more likely the code that controls shutdown knows the real temp, and it's just the temp I see that can be completely screwed by fourth-pin-manipulation. (Note that during all these tests I have a separate, external fan pointing right at the CPU to keep it cool regardless of how many fans are connected.)

This is really weird!

I tried connecting a few different resistors between ground and PWM with a 3-pin fan connected - 120k, 10k, 1k and 390Ω, all of which behaved the same: If connected on boot, I got the same 0.0 temps as usual. However if one of these resistors was connected between ground and PWM after booting (or disconnected and re-connected if already there from boot), show chass then showed the weird 128.0 temp I also saw when probing with my multimeter.

So.. I'm able to get some result? :) Not a very helpful one. I have no idea if I'm even on a useful path. Maybe it's actively monitoring this 4th PWM pin, despite it (I thought) being output only, and expects some specific and/or constantly varying resistance on it.

But can it even monitor the resistance of a pin it's also sending a voltage down? I suppose if it alternates between sending voltage and reading resistance. Maybe I should probe it with my oscilloscope. Not that there's much point; if it's doing anything complicated I'm not likely to be able to re-create it anyway.

My knowledge of electronics is sadly very limited. I'd really be grateful if anyone knows the first thing about fans/PWM etc and has any ideas. Maybe this concept of not working without a 4th pin is not uncommon?

I could just buy new fans, but now this feels like a challenge that needs to be solved :) Anyway they're out of stock, so I can't buy PWM fans for a few days regardless.

Or I could just run with 3-pin fans and unable to see temps and detect dead fans. I have some confidence that even though I can't see the temp, the shutdown routines probably can. Anyway if I just run the Noctuas at full speed, I don't expect to get anywhere near shutdown temps. It bothers me though, not being able to monitor :)
 
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TheBloke

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Sorry for all the posts, last one I promise. Two more things.

First:
  • If I boot with a 4-pin PWM fan in the fan 3 position (closest to PSU), temperature monitoring always works, even with two 3-pins also connected
  • If I then swap this 4-pin fan for a 3-pin while the switch is running, temp monitoring continues to work from that point onwards.
  • It breaks again if the next power cycle has 3 x 3-pins again.
But there's also something else interesting about booting with a single 4-pin PWN fan alongside 2 x 3-pins. The 4-pin.. pulses. I can hear it constantly spinning faster and slower, faster and slower. It defaults to fan-speed 2, and in this fan-speed 2 I can hear the constant pulsing. If I then set it to "fan-speed 1", the pulsing stops. And so does the fan. It stops moving completely, and a few seconds later "show chass" shows it as failed. If I set it back to fan-speed 2, it starts working again, doing the pulsing.

fan-speed 3 also pulses, but at faster speeds. It makes a much more noticeable whirr-WHIRR-whirr-WHIRR type sound.

I used the multimeter to monitor the PWM during this pulsing, and in "fan-speed 3" the voltage was fluctuating between 0.05 and 3.5 volts in a regular cycle. So more or less an on-off cycle, where at fan-speed 3 it should have been full on, all the time.

This of course doesn't happen when I boot normally with 3 x 4-pin fans, or even 1 x 4-pin fan. The presence of the 2 x 3-pins is causing this behaviour in the 4-pin.

So.. are the fans inter-dependent? Does having 2 x 3-pin fans connected at the same time as 1 x 4-pin cause the 4-pin to behave differently? Well it clearly does, but why? Are the 4th pin of each connector inter-connected somehow?

Secondly, I tried booting with 3 x 3-pin (no working temps), then unplugging fan 3 and connecting a 4-pin instead:
  • Once the 4-pin was connected, show chass showed the weird 128-degrees 'reading'
  • The 4-pin fan put into position 3 ran permanently at full speed, ignoring my "fan-speed" setting. From boot it only does this if fan 3 is missing. Indicating that post-boot it doesn't really detect this fan properly; or that there's a specific at-boot check for fan 3.
  • Unplugging the 4-pin fan and re-plugging it did not clear out the 128-degrees, nor stop the full-speed.
The first and second points together seem to indicate that both working temps and the presence of fan 3 have to be established on boot, and once established will stay working, but cannot be established later. In the case of the 128-degree reading, this is the same as achieved by my earlier dumb resistor test. So connecting anything to pin-4 after boot seems to give the 128-degree reading to temp monitoring, even if it's a real fan.

And maybe the first point also indicates that the three fans are considered together somehow - or at least, missing fourth pins on one or two of them causes weird behaviour in fan(s) that do have it.

Finally, the first point above lead itself to a potential workaround, albeit a pretty crappy one: boot with 1 x 4-pin fan temporarily connected, then disconnect after boot and plug the intended 3-pin fan. Thereafter temp monitoring will work with 3-pin fans.

Maybe usable in the short term, at least if I knew the switch was going to be running without power loss for days or weeks. But not a long term solution.

(Sorry to keep posting about this, probably no-one else cares.. just buy the 4-pin PWM fans! But I find it fascinating - something so weird is going on here. Lucky me to stumble into it because Amazon were out of stock of the fan I wanted :D )
 
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fohdeesha

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I believe it's a hardware/software watchdog. Both the fan speed and temperature sensors are all read through the same I2C bus. If it sees it's failed to get legitimate readings from multiple fans in X amount of time, it assumes the I2C bus has failed and the temperature readings it has are potentially bad, and forces them to 0 it looks like. This is one of several reasons why I always wondered why people put so much time and effort into fan modding enterprise gear - just stick the thing in a basement closet or something and forget about it :p

Also I really doubt it's going to attempt speed control on any fan if it can't get a legitimate RPM sense signal back from them (4th pin), so it probably just defaults them all to high speed

i dunno if you've dicked around with the power supply fans yet, but at least on the brocade's I've used, if the RPM reading from the power supply fans are less than 20 or 30% lower than what it expects (or no reading at all), it would refuse to boot and mark the power supply as failed. half the time it would fully boot, then shut off after a period of time marking the PSU as bad. There was a third strange failure mode where it would work fine, but if the power feed to one psu failed, it would not let the redundant 2nd PSU take over, because it was marked as failed, so it would just shut off

I went through the trouble of sourcing the exact delta fan replacements for the PSU's of a brocade FCX POE (which is about twice as loud at idle as an LB6M on full blast), except a 50% slower RPM model. They fit perfectly and had the correct pinout and everything, but it did not like the slower RPM. That was the first and last time I dicked around with modding fans

tldr: there are a LOT of software checks and logic to monitor all the various busses and devices in enterprise gear, a lot more than people realize. They're written on a set of assumptions about the data they'll get back (types of fans, speeds, etc). When you start modifying the hardware like this, expect them to start getting really ****y
 
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Todd Lynch

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I recently ordered an LB6M for my home lab and have been struggling with the CLI for the last couple of days. I'm just not "getting it." I'm no stranger to updating firmware and got both my LB6M and an LB4M updated to the most recent "stock" files I could find. That is to say, I'm familiar enough with the tools to do that particular job without much assistance. But the stock CLI is clunky and the Brocade interface is *definitely* something I'd prefer, even if I can only get it going on the LB6M.

I say all that because... I managed to brick my LB6M tonight trying to do the Brocade transition.

Long story short, I fat-fingered one of the commands when copying the Brocade bootloader - I wound up hitting an 'o' (letter, oh) where I needed a '0' (zero) and missed it before committing the command. Totally my fault. My terminal session went completely unresponsive for over an hour and still won't recover. I feel like an idiot admitting it but that's what happened.

It's one of the new, in-box units from UnixPlus and I'd rather not just toss it as a $300 mistake on my part and have to order a new one. I'd prefer to recover it, if possible, using the JTAG pins I've heard about but I'm a little lost getting that deep into the hardware and haven't used JTAG in any capacity before.

Can anyone offer some how-to or advice on what I need to do at this point? If there are parts I can buy to do this, I'd prefer that over soldering things on my own unless there's a crazy cost difference. Other than ordering another unit from UnixPlus, I don't have much to lose and, maybe turning this into a positive, I could serve as a good point of documentation for anyone else that gets stuck in my situation down the road.

Thank you for any help any of you can provide.
 

fohdeesha

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I say all that because... I managed to brick my LB6M tonight trying to do the Brocade transition.
We have our very first Quanta > Brocade brick! Congratulations - I'd give you a sticker but we haven't had any made :p

Long story short, I fat-fingered one of the commands when copying the Brocade bootloader - I wound up hitting an 'o' (letter, oh) where I needed a '0' (zero) and missed it before committing the command
This is *exactly* why one of the first things I put in the guide is to only copy and paste commands, do not try to type them out :)

If you did indeed brick it, the only solution is to use a JTAG unit to put the bootloader back onto the onboard flash. However PowerPC-capable JTAG units generally run about the price of a brand new LB6M. However I ordered a PPC capable unit last week to do some further hardware debugging.

I'll unbrick your LB6M for free if you pay shipping both ways (shipping it to me, then shipping it back after I JTAG the bootloader back on). If you want to calculate shipping I'm in indianapolis Indiana, 46280. If you're in a major metro area in the US I'd guess shipping with fedex would probably be about $20 each way.

First though, I would confirm you actually bricked the thing. The only way to brick it is erasing and/or overwriting the bootloader incorrectly, and doing that wouldn't immediately make the terminal unresponsive like you said yours did, since the bootloader program runs from RAM. it sounds like you might have accidentally overwritten a location in RAM it was running from. To check, just pull power from the switch and then power it back on, see if it comes back up
 
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Todd Lynch

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Re-flashing it via JTAG with your equipment would be mighty kind - thank you! I'm in the Minneapolis area so it shouldn't be too bad for shipping.

I know it's bricked. I had already issued the delete command before I sent the bad copy command. The putty window was unresponsive. I closed it and attempted to re-open it but the LB6M wouldn't give me any response. At that point, all I could do was pull the power and pray I didn't totally hose it. Unfortunately, while it now powers up, I still get nothing from the serial port nor do the fans spin down.
 

Terry Kennedy

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  • If I boot with a 4-pin PWM fan in the fan 3 position (closest to PSU), temperature monitoring always works, even with two 3-pins also connected
  • If I then swap this 4-pin fan for a 3-pin while the switch is running, temp monitoring continues to work from that point onwards.
  • It breaks again if the next power cycle has 3 x 3-pins again.
There is a common mis-perception that the 3rd wire on 3-pin fans is always speed control and the 4th wire on 4-pin fans is always speed monitoring, because that is usually how PCs use 3- and 4-wire fans. That isn't the case and even if it was, there are many options just for speed monitoring. To get an idea of what sort of combinations there, look at this Nidec PDF. This is one reason I don't buy "modder-class" fans - I want fans with detailed datasheets, not (at best) an airflow graph or two.

As someone else pointed out, fan speed monitoring and temperature sensing are probably running over a single bus. The switch was designed with speed-monitoring fans, so by definition if no fans are reporting a speed signal it is more likely that there is a single failure affecting that bus than all 3 fans failing that way. The hardware and software designers didn't forsee users who wanted to change out all the fans for incompatible ones. :p
 

TheBloke

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I got a hack working :D

Using a 3-pin fan with a 120k resistor between +12V and the empty fourth pin = working temps, working fan detection:
Code:
fan 1 failed
fan 2 failed
Fan 3 ok, speed (manual): 1<->[[2]]<->3
Fan controlled temperature: 32.0 deg-C
..
Exhaust Side Temperature Readings:
        Current temperature : 32.0 deg-C
        Warning level.......: 80.0 deg-C
        Shutdown level......: 90.0 deg-C
Intake Side Temperature Readings:
        Current temperature : 30.0 deg-C

@Terry Kennedy thanks so much for that PDF. I know you meant it to show me the vast variation in fans, but it was page 2 that got my hackaday solution working. It had the circuit diagrams I had been failing to find earlier, in particular showing a pull-up resistor between 12V and signal, in the Tach diagram.

I tried multiple resistors earlier against ground, but was a bit worried putting one to 12V. After seeing the diagram, I tried it, and boom! Not literally 'boom' :D

And the good news is this is only needed on one fan - the one in position three, nearest the PSU. This appears to be the key fan probed on boot, which has to pass the checks for temp monitoring and fan detection to work. I'm running now with this fan modded with the resistor, and the other two just connected direct with 3-pins, and it's fine.

I thought this was proof that, as you guys cautioned, the wires were not in the order I thought. I thought the fact that a pull-up resistor on pin 4 meant pin 4 must be actually the Tach pin, where such a resistor is included in the design. But as I have later discovered and will describe in my next post (volume 9 of this epic tome..), they're clearly not swapped, and swapping over pins 3 & 4 breaks things in the same way as using a 3-pin fan.

i dunno if you've dicked around with the power supply fans yet, but at least on the brocade's I've used, if the RPM reading from the power supply fans are less than 20 or 30% lower than what it expects (or no reading at all), it would refuse to boot and mark the power supply as failed. half the time it would fully boot, then shut off after a period of time marking the PSU as bad. There was a third strange failure mode where it would work fine, but if the power feed to one psu failed, it would not let the redundant 2nd PSU take over, because it was marked as failed, so it would just shut off
Already done the PSU and thankfully no such problems. In fact I'm running them in 2-pin mode, so the PSU is not getting any tach data. Works just fine. I tested this before re-wiring and confirmed that it would in fact run with no fans connected at all (with an external fan blowing in for safety during the brief test.)

That said, I'm only ever running with a single non-redundant PSU (I've not modded the second one.) So I could theoretically be hitting your third failure mode and just wouldn't notice. But if I am, that's the only one I could be hitting - I get "Power supply 2, status OK" on every boot.

In the case of the PSU fans, the wiring was already known to be in a different order to 'standard', and the Noctua fans I used come with adapters to adjust the pin ordering easily for this case . I could have connected the Tach pin as well, but as I knew it worked without, I didn't bother as wiring space within the PSU case is very limited.

- just stick the thing in a basement closet or something and forget about it :p
If I had a basement, I wouldn't be going to all this trouble :p My original plan was to put all my gear in my separate garage, but that requires a lot of cleanup work in the garage as well as planning a safe and tidy way to run multiple sets of 10G and 1G cables out through the wall of my house, through 10' or so of front garden, and then through the garage wall. I've investigated the necessary cabling, but working out where/how to dig up the garden - or a suitable route around the garden - is a bit more complex.

I will hopefully still do that in the end, but doing this noise reduction work for my switch and server means I don't have to tackle it at least until the late spring/summer, and can now run my HW 24/7 in the meantime without driving myself completely crazy with noise :)

Anyway, wasn't all this a far more interesting and engaging exercise than just running with stock fans? :) Well for me anyway :)
 
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TheBloke

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So during my previous tests, I thought maybe pins three and four were swapped. They're not:

I re-wired a 4-pin extension cable to swap pins three and four. Used with either my 3-pin replacement fan or a (non-original) 4-pin PWM fan, this exhibits the usual problems: no temp readings, no fan control, no fan monitoring.

The overall results are:
  • If I plug in a non-original 4-pin PWM fan (a normal PC case fan) directly: I get temp figures, I get fan detection, but I don't get speed control, and it seems to always run at a slow or slowest speed. Except on boot, where it briefly exhibits the normal behaviour of running at full speed during bootloader, then dropping to a lower speed.
    • Also, some fans will then go failed a short while after boot; eg my 12cm Noctua fans do. But my 20cm Noctua does not, nor does a 12cm non-quiet Corsair. Difference in reported RPM speeds maybe? But the 20cm is the slowest of the lot, max 800rpm, and I would have assumed low speed = more likely to be considered failed. But might well be more complicated than that.
  • If I plug in a non-original 4-pin PWM fan via a swapped 3rd & 4th pin: No temp figures, no fan detection, no speed control
  • If I plug in a non-original 3-pin fan, either directly or via the swapped cable: No temp figures, no fan detection, no speed control, but runs at full speed.
  • However, if I plug in a 3-pin fan directly with the addition of a 120k resistor between its +12V pin and the unconnected 4th pin of the connector: Working temp figures, working fan detection, full speed.

So it looks like my nasty resistor hack may actually be the best overall solution, barring any further discoveries. I could buy 40mm 4-pin PWM fans to get temp readings and fan detection, but they'd have no speed control and worse, would run at a fixed low speed, which on quiet 40mm fans is quite likely too little airflow.

I studied in more detail the lengthy fan catalogue published by AVC, whose fans I have in my LB6M. One thing that might relevant - I note that the fans I have are marked as having both a "Tacho" signal and "Rotational Detection" signal, which is described as: This is the simple “Go”/“No-Go” fan signal output to alert the system if the fan is not functioning. It doesn't say which wire this is on, but the obvious assumption would be the same Tacho wire. Though it would make more sense if it was actually on the PWM wire, as that would explain why 4-pin fans generally work and 3-pin don't, without a hack to the fourth wire.

Anyway, yes, I certainly do take you guys' points that these things are much more complicated than swapping out fans in a PC mod :)

There's also the fact that, as I think one of you said, the switch was designed for and tested only with very specific fans. They might have put in some quite specific checks, for example for particular current draws that these fans will always exhibit when working properly, and any other fan is unlikely to.

I think I shall end up making one hacked wire with a resistor for fan position 3, and running with my 3 x 3-pin fans and just leaving it at that. Not sure much more testing will bring any useful result :)

I am still surprised though that I can't seem to find a definitive answer. Docs like the AVC hint at possible differences - eg the Rotational Detection - but I would have thought I'd be able to find some doc specifying exactly what signals are sent. The PDF Terry gave showed that to some extent for one brand of fan, but despite the AVC catalogue being 138 pages they don't seem to feel the need to explain the full details. They don't even give a wiring diagram. I suppose there must be be other documentation that's not been made accessible without a purchase. I did find this useful Intel specification document on Tach and PWM, though that makes no mention of Rotational Detection nor monitoring the PWM pin.

I probably came into the switch mod with a bit too much (over-)confidence, especially as before doing the switch I swapped out all the fans in my server (Tyan LGA1366 motherboard) with Noctua fans and it worked just fine, interfacing perfectly with the motherboard and IPMI's fan control routines. I do get that integrated components are a somewhat different ball-game, and not intended to be anywhere near as plug-and-play.
 
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Terry Kennedy

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I am still surprised though that I can't seem to find a definitive answer. Docs like the AVC hint at possible differences - eg the Rotational Detection - but I would have thought I'd be able to find some doc specifying exactly what signals are sent. The PDF Terry gave showed did that to some extent for one brand of fan, but despite the AVC catalogue being 138 pages they don't seem to feel the need to explain the full details. They don't even give a wiring diagram. I suppose there must be be other documentation that's not been made accessible without a purchase. I did find this useful Intel specification document on Tach and PWM, though that makes no mention of Rotational Detection nor monitoring the PWM pin.
I was trying to find where you mentioned me and had a question on open collector, and you edited your post between when I read it and I tried to reply. :p

Anyway, the speed sense output (which can be either the 3rd or 4th wire) can be a tachometer pulse (normally 2 pulses/rev, but this varies), locked-rotor alarm (fan not spinning at all), low-speed alarm (typically 70% of expected speed on a fixed-speed fan, etc.), some combination, or something completely different.

Open-collector just means that the output is (normally) pulled to ground to indicate one state of the signal, but the other state of the signal "floats" and it is the device's responsibility to pull that signal up to the desired level with a resistor. For a device using 12V fans and 5V logic, the pull-up would normally be to the 5V line and not the 12V line, as having the logic see 12V would not be a good idea.

Look at page 21 of the AVC catalog for their version of the Nidec "secret decoder ring". Note that none of these manufacturers will tell you in their catalogs which versions are stock and which versions are special-order. You need to look up part numbers on places like Digi-Key to find that out. Woe to anyone who has a special-order fan and doesn't need thousands of them (I used to maintain systems where the cooling fans were 35V AC, 70Hz, square-wave instead of sine-wave) o_O.
 
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TheBloke

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Brighton, UK
Well after all that messing about with 3-pin fans, I ended up going back to an earlier idea and used 1 x 4-pin 12cm :)



It works out both quieter and cooler than 3 x 40mm, and doesn't require a resistor hack to get temperature monitoring. When sitting idle in an ambient temperature of 21°C, it settles on 50°-52°C. Compared to 60°-62° with the 3 x 40mm at 3700 RPM (ultra-low-noise adapter), and around 56°C when they were at 4400 RPM (low-noise adapter.) I don't know what speed the 12cm is running at, but I'm guessing it's around 800.

Main thing that doesn't work is fan detection. For some reason the switch doesn't like something about the Noctua 12cm fans and marks it as failed shortly after boot. Not sure why - it's not related to low RPM, as my Noctua 20cm runs at 400-800RPM and that worked fine. And other 12cm fans worked OK. Another peculiarity of the fan monitoring in this switch.

But no big deal. With only one fan it's either working or not, and if it stops working the temperature will rise fairly quickly and I'll pick that up in monitoring.

I also can't control the speed of the fan - the switch always runs it at what looks like its slowest speed. But that's turned out fine as it's cool enough, and of course nice and quiet at this speed. Most or all of the noise I can hear is from the 2 x Noctua 40x10mm fans in the PSU, which I let run at their full speed.

Compared to stock it's like the soft breath of a whispering baby mouse. I'd say it sounds something like a basic desktop that has a single stock CPU fan running at low-mid speed. Not silent when it's right behind me, but barely noticeable. And when I have it back in my office's annex area it should be inaudible.

Going with the 12cm has also freed up the 3 x 40mm in case I decide to also use my LB4M 1GB switch daily, in which case I can quiet that as well.

Any road, I've spent far too much time - and more money than I care to admit to - on all this quieting business, so now it's time to go back to actually using all this stuff :) But I can now run my server, switch and disk tray in the house without it being a constant annoyance.
 
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Todd Lynch

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Jan 26, 2018
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Just recovered @Todd Lynch 's LB6M - it's amazing how fast and easy that is once you spend the money on the right tools. Will ship it back out tomorrow! Hopefully that's our first and last brick :)

Imgur: The magic of the Internet
Confirmed received and in perfect shape. Again - thank you so much!

EDIT TO ADD: What was the outcome of the management port coming up at 100/hdx? I'm doing some basic setup and noticed my management port is showing up as 100/hdx while the the other end is connected to a Cisco SG200-08 (1000/fdx capable and advertised).
 
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BlueTip

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Feb 4, 2017
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Hi, All,

I have been designing a 3D printable fan tray that expands out to 2x80mm fans. The progress is slow as I'm new to 3D printing and I'm relying on the public library print services. However, after three prototype prints I'm really close to a first working design. Here's a rough picture that still needs bolt holes, a couple tweaks, and final fitting. I don't have a very good measure of running temps yet, but I'm confident they'll be <40C with fans pretty quiet on max.

@TheBloke... It's funny we were both messing with the fans around the same time and I can confirm your findings regarding the key fan for monitoring being fan number three next to the PSU - if that one isn't working, you won't see any temperature reading. Also, I can tell you that I have had ZERO luck with Noctua fans in that position (tried NF-A8 and NF-R8 with no luck). What DOES work well for me is the Arctic F8 PWM (5-pack purchased on Amazon). My plan is to populate two fan connnectors and share the tach for the third.

The great thing about this mod is that it's 100% reversible! No cutting! The original fan tray comes out, fan control board is transplanted, and the new expander tray goes in. The intention is to use bolts and washers to fasten the assembly to the existing fan bolt holes.

model1.jpg

Wish me luck, and stay tuned!
 
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Andras

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Mar 28, 2017
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Hi,
Could someone help me?
I have 2 LB6M switches, stock fw, configured as I thought it should be.
Both switches are configured and all ports are set for mtu 9216 but for some reason all machines that are connected to the second one have normal connection and speed only if the mtu is set to 1500.
The first switch is configured the same way but on that one the mtu 9216 is working correctly, machines that are connected to that switch have normal net connection and speed if the mtu is set to 9000.
Here are the running configs of the switches
Thx
 

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TheBloke

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Feb 23, 2017
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Brighton, UK
I have been designing a 3D printable fan tray that expands out to 2x80mm fans. The progress is slow as I'm new to 3D printing and I'm relying on the public library print services. However, after three prototype prints I'm really close to a first working design. Here's a rough picture that still needs bolt holes, a couple tweaks, and final fitting. I don't have a very good measure of running temps yet, but I'm confident they'll be <40C with fans pretty quiet on max.
Wow, that's an impressive solution :) I can see the appeal of not needing to cut a circle in the top panel, in case one later wanted to sell it.

Hope it all goes smoothly for you.

@TheBloke... It's funny we were both messing with the fans around the same time and I can confirm your findings regarding the key fan for monitoring being fan number three next to the PSU - if that one isn't working, you won't see any temperature reading. Also, I can tell you that I have had ZERO luck with Noctua fans in that position (tried NF-A8 and NF-R8 with no luck). What DOES work well for me is the Arctic F8 PWM (5-pack purchased on Amazon). My plan is to populate two fan connnectors and share the tach for the third.
Yeah the fan detection is weird. I have had one Noctua fan work - the NF-A20, their 200mm beast. But none of their 120mm ones worked. I didn't bother trying any others, but it's good to know the 80mm doesn't work either.

So with the Arctic fans, as well as having them detected OK, do you also have functioning PWM control? You can change their speed from the switch (eg set fan-speed [1-3] in Brocade FW)? That's broken along with detection with my Noctua fan, though that's turned out to be OK because without PWM control it runs at a low/lowest speed, and that's proved perfectly fine for temperature.

My 1 x 120mm fan mod is holding up well. Completely silent when the switch is located in the annex area of my office, about 5 metres and around a corner away from me. Temperature holds steady at 50-52°C when ambient is 20-23°C. And I can get it as low as 40° if I open a door in the annex that opens into an undeveloped roof crawl space, allowing air to circulate which is at 10-15°C (at least for now, in the current wintery climate.)

One thing I didn't mention before: as well as modding the fan I also changed the thermal paste on the main CPU heatsink, using expensive enthusiast/overclocker's stuff instead. For some reason I didn't properly record before/after temps, but it may be helping to reduce temp another 2-4°C or so.

Good luck with your mod!
 

BlueTip

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Feb 4, 2017
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