Topic: BFL ASIC Firmware & Hardware, Understanding & Optimization (Read 15651 times)

Ended up replacing my fans with:
VORTEX CF-V12S
70 CFM and 17.7 dB each.

Removed the side panels because they block the airflow like hell, whoever designed them should be fired.

Temps is now 68-70C and sound is manageable. Can sit on skype and play computer games in the same room without anyone complaining.

Replaced with GT 1850 on both end, much lower noise, temp down to 58c. But the mod that remove the 92MM fan and add a forced airflow channel does not work for me, temp went over 70c in a couple of minutes. Changing the 92MM fan to face downwards also does not work, that reduced the overall airflow speed through the box, thus raise the temp eventually, seems the pull configuration is there to improve the overall airflow

I am running the 60GH/s devices naked, with 92mm Noctua NF-B9 fans.
I have Honywell HY900E fans blowing the heat away on fan level 1
The acoustics are 42db for 3 miners 
My temperatures are between 65 and 77

I have a feeling that the Noctua's I have have have a lower airflow than the BFL fans. I cannot measure this, and the BFL fans have no markings on it.

Good luck

Getting new fans for the Single tomorrow. But, what cfm value should I atleast have on my new fans?

Anyone know what cfm the original fans have? (cfm = airflow).
And also, do I need to have PWM fans?

Nice to see a thread about the Bitforce SC Noise

Once the 4 Bitforce SC 60 GH/s devices were set up I was in shock, I was expecting something just a bit quiter considering the original spec of one fan.
Most people bought these to run at home, not in a data center where they belong.

When I searched no water cooling solution.. aagh!
Running out of time before my second order shipped, I converted my second delivery slot because the insane noise 4 these devices make, I could not risk doubling the noise in my middle flat fearing the noise violation police running 4 more miners.
I now am on the waiting list for a year hosting of 500GH/s, hope I get ROI.

Now to solutions.
I read a post here to reduce the loud acoustic level, what do you guys think?
I am thinking that they offer a quieter SC than the modified end panels.
http://www.ewal.net/2013/08/15/bitcoin-mining-update-butterfly-labs-sc-singles/

I have also seen prototypes of the Waterblock, and modified end panels which offer 10db noise reduction which could help a lot.

@BTC-engineer:


Have you found a acceptable fan-replacement?

(oder hab ich das hier irgendwie überlesen... mein englisch ist nicht so lecker..) :-)

Gruss Z80

I did here: https://bitcointalksearch.org/topic/bfl-single-air-flow-286326

Pick a Noctua fan, which is claimed to last about 160,000 hours (who knows, maybe it's handy to have a working, second-hand fan at hand in 2029 ;-), it hardly makes any sound and you can mod your miner to stand in a vertical position (putting the fan horizontal) for even more efficient cooling.

And oh, btw, they're ugly pinkish with brownisch details. Imho still better than any led decorated fan...

Other than the plates, did anyone made any other mods that significantly reduced  the noise? What would be the quitest fans out there and is it even worth replacing them?
I would expect to at least half the DB, otherwise i'll just need to find a storage room to place it.

This thing is impossible to be kept in a room where people try to do something, it's like a jet fighter

I just wanted to comment on the fan plate set that I received from Germany yesterday.  First of all, I was pleasantly surprised to receive it in only 12 days considering it was shipped from Germany to Canada.  It was super-easy to install onto my Little Single -- only had about 5-10 minutes of downtime to remove the old fan plates and install the new ones.

I wanted some quantitative measurements of the impact the plates had, so I made some before and after measurements.  Sound level was recorded using a Radio Shack 33-2050 sound level meter (analog), set to "A" weight and slow response, facing the intake of the LS and spaced 20cm away from the unit.  The ambient room temperature is 21.4C.

Before:
  Sound Level: 74dB
  Temperature: 68C

After:
  Sound Level: 67dB
  Temperature: 61C

Not bad for such a simple modification!  I wasn't expecting a miracle - I mean, these units are LOUD and there's no getting around it.  Now it's slightly less loud (but still loud).  That's mainly why I keep it down in the nice cool basement - so nobody can hear it.  I'm guessing that replacing the fans with quieter models would help, too - but the more I mod this thing, the less ROI there will be to be had (and having only received it on Sept. 2, it's days are already numbered).

Anyways, just wanted to thank you for making these plates available and even if it's not making my hashrate go higher, at least it's running the unit at a cooler temperature which should help its longevity (or perhaps give more headroom for overclocking, if it ever becomes possible for lay-people).

I do indeed.  Now fixed in the original post.

I think you mean @BTC-Engineer, but yes, I was just about to ask this same question  

Just to say I bought a set of the fan plates on bitmit and am pleased with them.  Apart from looking better, they do reduce the noise from the airflow.

But don't expect too much of an overall noise reduction from this mod alone.  At least on my unit, the fan motor/bearing noise is significantly louder than the airflow noise - and of course the improved fan plates won't do anything about that.

@BTC-engineer:  any progress on finding replacement fans that run quieter without compromising the airflow?

roy

temp dropped at the place where this sensor is, but what is the temp near the chip where big fan sucks air out? what is the temp underside of pcb ?

watching

Just taking the whole cover off on my 2 reduced the temp by 5C each
It initially dropped 7C on one but levelled out at 5C for both.

It turned out that the MOSFET zone usually gets to be the hottest region on the PCB. As a result we use our temperature sensors on board for sensing temperature, otherwise the on-die temperature diode
is fairly easy to read (Just check the voltage drop across the diode and you have the temperature).


Regards,
Nasser

Need an air filter... that is going suck in the dust for sure.  https://www.bitcoinstore.com/accessories/air-filters.html

Gentle typhoon 1850 rpm 120mm fan should be able to reduce the noise dramatically while keep almost the same static pressure and air flow

It'd be nice to have a video that actually shows how much this improves the noise level and temp.

Latest shipped SC60 Ser#13xx  has
DEVICE: BitFORCE SC0x0aFIRMWARE: 1.2.90x0aIAR

loaded, any source available?

New version is online, I've added some new checks to ensure the FTDI drivers are actually there before starting up (if they aren't, a warning is displayed then the program closes.)
Also added a slightly longer delay in the loop checking for new serial data, which might make it collect data a fraction slower, but should resolve the issue with no diagnostic information being displayed on slower machines.

Link below:
http://randomcontent.wolfnexus.net/RandomSite/files/9613/7838/3202/RW2-BFL-Commport-Scanner.zip

Indeed false positive

https://analysis.avira.com/en/status?uniqueid=gbsQSnjX5hY3ISq4jnUXLNW56pYPInVK&incidentid=1502551

Regards

Well, as the author of the software I can guarantee there is no dropper in it. It may be detecting the reflection I used and the embedded wrapper DLL file for the FTDI drivers, but that shouldn't trigger a detection as a dropper... Send it through to the AV company, I'll privmsg you an email address to contact me with if you want too.

Just an FYI - the cgminer API has always reported that in the stats command.

Hi BTC-engineer,  good work you are doing with this stuff, I've got a Litle Single that Red_Wolf_2's software throw this data:


After few reboots I get 116-118 engines, that gives me 31.5-32  GH/s, any improve if I update my firmware? seems to be quite old.

Regards

Understood, Thanks.  I have an April version board but have not looked into flashing yet as there seems to be no benefit for me after potentially dropping money on an AVR dragon. There would need to be a gain for me to start messing around...for now.

Neither Symantec nor McAffee alert for this.  The likely reason yours does is that it is seeing the port-scan portion of the software which would indicate a potential unsafe program if you did not already know what it is doing.  If you want to be absolutely sure, send it to the AV company and ask them to verify it is not a false positive.

Sorry but my antivirus is unhappy with your software

Well, that's not exactly what I said or would like to say. I would not say it so much in general like your consumption.
I used a SINGLE-SC in the 5xx serialnumber range, which I received ~2weeks ago. Flashing the standard 1.2.8 firmware into this single gave me a significant lower hashing rate than me already tuned 1.2.6 firmware. This was not soo much surprising for me. But after tuning the 1.2.8 firmware in nearly the same way I did it with the 1.2. 6 firmware, I still could not reach the hashing rate of my tuned 1.2.6 firmware. Maybe there are other ways to tune the 1.2.8 firmware to get better results. However, with the standard 1.2.8 firmware I could not see any improvement in hashing-rate over the standard 1.2.6 firmware with my single, which seems to have revision A chips.

So what your saying is with older versions of the hardware, newer firmware doesn't really bump performance any and doesn't seem to be worth the flash?

I've just tested firmware 1.2.8 on one of my singles.
It looks like this single, which is my latest one received ~2 weeks ago, has not yet Revision B chips inside.
Anyhow, I could not reach the overall hashing performance, which I reached with 1.2.6. So I switched back to 1.2.6. To be fair, I didn't spend a lot of time with the new firmware. I will test it again, when new singles arrive.

Firmware version 1.2.8 is released. I will test it soon.
It looks like there is a way to use ENGINE_ZERO if the ASIC has revision B, but BFL seems to worry about heat-problems.
I can only repeat myself by saying that one of the most important things is to have a good airflow through the box.
With my improved fan plates, the box is not only quieter, you have also way for hashrate improvements.

---------------------------------------------------------------------------
/*************** Firmware Version ******************/
#define __FIRMWARE_VERSION      "1.2.8"   

// **** Change log Vs 1.2.7
// - An option introduced that disables Engines 0 and 1 on all chips. This is to throttle the speed so the unit won't overheat
//   ( in std_defs.h named as DISABLE_ENGINE_ZERO_AND_ONE_ON_ALL_CHIPS)

// **** Change log Vs 1.2.6
// - Engine 0 operation supported
// - Auto detect if chip is Revision B or A (Revision B has engine 0 functional)
// - Blink issue resolved. Now it blinks for 30seconds instead of 300ms
----------------------------------------------------------------------------

I'm now wondering what these two defines in the firmware do... Anyone experimented with them?
//#define __CHIP_BY_CHIP_DIAGNOSTICS      
//#define __ENGINE_BY_ENGINE_DIAGNOSTICS

I'm imagining more in-depth self-diagnostics on bootup, but if there is a chance the chip-by-chip diagnostics would allow individual chips on boards to reclock to higher maximum speeds it would definitely be interesting to play with...

Also, I've been working on a windows program to make it easier to grab statistics from BFL Bitforce SC gear. Far from complete yet and it only supports FTDI drivers, but its available from http://randomcontent.wolfnexus.net/RandomSite/files/2313/7776/5140/RW2-BFL-Commport-Scanner.zip

Yes it is an executable, but I can promise it does nothing malicious. Below is a summary of how it works.

Startup - unpack required wrapper DLL from within using reflection
Check for running cgminer or bfgminer instances. Display warning if found, lock interface and skip subsequent scans
Scan for FTDI devices using WinUSB driver, if found display warning
Scan for FTDI devices using unknown driver, if found display warning
Scan for FTDI devices using FTDI driver, identify which of these are Bitforce SC units and add them to the listbox

On selection from listbox, enable scan device button. If nothing selected in listbox, ensure button is disabled

On scan, open port based on device serial number. Issue ZCX, ZTX and ZLX commands and populate relevant fields on the user interface.

Thats about all there is to it, besides some other bits of logic to keep the UI clean.
If anyone finds any bugs, please let me know. I've done four or five iterations so far to fix major bugs.

Again, this is a Windows only program, and has been tested on XP and Windows 7 so far. It is written in .Net (because I am lazy) and isn't really open source, although I'm happy to discuss the code if anyone is interested.

Here is a picture inside the cabinet before the fans were installed.

http://subjectreality.com/miner/cabinet2.png

I built a cabinet to reduce the sound of my BFL 60GH/s miner. It has three chambers insulated with foam. There are four 120mm intake fans pulling cool air in from the floor and another four pushing out the back at the top. I built a little power supply for the fans that draw 15 W. I had hoped to sit the miner vertically pushing air upwards but it won't run that way.

The temperature is about 2-3 deg C higher which I will work on. 59 on the floor is now 63 C in the cabinet. It is significantly quieter and I expect to be able to sleep now.

 http://subjectreality.com/miner/cabinet.png

I understand, making a fan grill is a challenge.



...and in all honesty, it is an improvement. (who designs these original pieces?)

Those who can read have a clear advantage.
BTW: Are you not the one who first corrected me, as a non English native speaker, after my first posting in this thread, by not only just telling me what I've done wrong. You quoted a multi-page posting, just to point out one wrong spelled word. This really helped a lot!

To answer your question, just to avoid that anyone thinks I like this confusion.
I guess you mean BFL-Engineer, also known as Mr. Nasser from BFL.
I'm BTC-engineer. And just for the case - I was first here.
 
You would do me, and I guess most others also a big favor by avoiding this topic or even better, reducing your 'activity' on a Kindergarten section in this forum, for users without a real life.

That is very embarrassing....

I will eliminate any topics misdirected at BTC-Engineer.

@ BTC-Engineer

I'll leave some posts so that continuity across the thread makes sense. I offer my apologies on mis-identifying you.

https://bitcointalksearch.org/user/btc-engineer-49711

vs.

https://bitcointalksearch.org/user/bfl-engineer-52443

I also feel sad that this is not possible. Always the same "users" who take over every thread with their unqualified postings.
I think the most serious members know what I mean. I really wonder, why the moderators are not talking any steps to avoid this chaos.

Who are we talking to then?

I don't think you are talking to who you think you are.

Can we have at least one thread where people can ask serious questions without the constant baiting!  There are plenty of threads bashing the manufacturers, so can we have a grown up questions and answers thread without constant bitching?  Or is that beyond us?

Yes, I've tried this with one of my first 60GH singles running firmware 1.2.6
The starting temperature has a little impact on the initial diagnosis test, but this is only minimal. More important is, that I could not simple always say that as more cool the unit is as more powerful the hashing result is.  The reason for this in firmware version 1.2.6 is, that it doesn't help you, when the diagnosis test is calculation wrong results based on wrong extreme starting temperatures. If the engines are clocked too fast and the unit is getting more hot, the HW-error rate is probably much increasing..

So my short advice. Forget it. Try to keep your unit constantly cool, this helps.

Has anyone tried the fridge trick with a mini single?  Mine is hashing at a steady 31 Ghash per sec, so I am reluctant to stop it and play around if it doesnt work?  Any idea on the extra perfromance you can expect?

This question can not answered in general. In case of the BFL ASIC or BFL products you have to ask BFL.
The only think I've designed up to now, which is related to the BFL single-sc product is the improved version of the fan plate.

I agree, I also think this is the reason why they didn't use this pins.
Anyhow, this pins are not connected on BFL's PCB designs. At least not from reading the jala schematics. I guess the single-sc design is not different in this point.
So no (easy) way to use them in existing BFL products.

@MrTeal: Did you use this pins in your design?

My guess is that the reason to use external sensors is that the internal ones are too noisy and very inaccurate. The cost is indirect: they can't afford to design the de-noising hardware/software and can't afford to properly characterize and calibrate the internal sensors.

It is actually quite common problem: many SoC chips have on-die temperature sensors but use external ones because otherwise they wouldn't meet the time-to-market goals. This includes even very-well capitalized entities which already have the methodology and the tools available.

No, those set the chip address (0 to 7) in the SPI chain. The temp diode is ball M8 and M9.

I'm guessing those on-die temp sensors are the pins labelled ADRS0, ADRS1 and ADRS2?

The current BFL chip has an on die temperature sensor, they just aren't using it. If I had to guess it's a cost issue; it's cheaper to toss a couple 20 cent temperature sensors on the board that it is to properly mux and read 16 temperature diodes.

Is the next generation (Monarch) going to have a true (die level) temp sensor?

Not necessarily. The DC/DC supply generates a significant amount of heat as well, and doesn't have the benefit of the nice heatpiped cooler attached to it. It's possible that the temperature reported from the sensors close to the output inductor could be higher than the die temperature.

I'm happy to announce that my friend is producing  this improved FAN PLATES and he is selling them on www.bitmit.net.
 
His account name is wowo and I can confirm that wowe is the official manufacture of my fan plate design.
Look on bitmit for 'FAN PLATE SET for BFL SINGLE'S'. I'm sure you will find it there.

Yesterday I've received the improved version of my single fan plates from production.


Here are some pictures of my singles with the new plates. Air is now flowing much easier.







It's easy to see the difference, when you directly compare it with the standard version.


A friend of mine has made them on his professional CNC-machine based on my design.
I've ask him if he would produce and ship them in very low volume too. And he agreed.

He would even produce them for order volume ONE.
He is thinking about a kit including:
2 x Improved fan plates
2 x fan grills
8 x screws

The plate is made fully compatible to the existing one (same backside profile).

Update: He is selling the sets now on www.bitmit.net
His account name is wowo and I can confirm that he is the official manufacture of my fan plate design.
Look on bitmit for 'FAN PLATE Set for BFL SINGLE'S'. I'm sure you will find it there.

Has anyone swapped the fans in the little single (30ghash) device?

The fan noise is driving me nuts and I'd really like to get something a little quieter.  They are running below 60c with stock fans.

Any suggestions on what to purchase?

In effect, what you are saying is...the chips are actually hotter than reported. Correct?

Is that a good thing?

I dont get this, do you have dedicated hvac to the units?!?! that are right next to you?

Also Celsius vs Fahrenheit?

Sorry that was misleading. Two things to add. 1) running caseless and 2) unit sitting next to a house AC vent. (not always on but helps)

EDIT: Did you ever have one of them days where nothing comes out right?  Of course Gomeler

Please note that the two reported temperatures from the single-sc are not everything. This values are coming from two sensors, which are somewhere between a 8-ASIC cluster and the +1V regulation for this cluster. They are not in the ASICs or inside the 8-ASIC cluster circuit nor inside the +1V regulation circuit.

Even if you may see only a small temperature increase by changing the fans or even see a decrease by changing the whole setup by e.g. opening the box or something like this, it doesn't mean that the ASIC's or any other important parts are not getting much more hot than they should. Also watch the hardware error rate carefully!

Soon I'm ready to report my results from looking for fan alternatives....

Huh? How are you cooling below ambient with just a fan?

Highest is 68degC in a 76degF room. Not too bad for making it much easier to sit next to.

EDIT: Just a big DOH!

What type of temperatures are you seeing now?

I swapped out the original fans for the corsair high static pressure fans and temps seem to be doing just fine with much less noise.

These guys: http://www.newegg.com/Product/Product.aspx?Item=N82E16835181027   Of course YMMV.

Please post some pics once you get the new CNC produced plates installed!
I'm curious what the cost of the new plates was? I'm sure others would be interested in getting some if they dramatically reduce the noise, my little single sounds like a hair dryer going non-stop. Maybe something for a kickstarter to produce a batch ...

Looking forward to updates on any fan changes as well, anything to reduce the noise of these units.

Thanks for the great post.. some of the same conclusions I've reached myself.

-- 60GH singles are already using 'binned' A-grade chips, so there's very little room to turn them up. almost not worth trying.

-- default cooling is decent, but doing it yourself is much better. I had a failed fan out of the box, so I had to replace fans day-0. I took some Scythe 120x38MM fans I had laying around from projects, and replaced the stock ones.  Dropped my average temps by 10-15C under load. (To BFL's credit, they had a replacement fan to me within 3 days... kudos to BFL_Jody)


-- worth mentioning and pesky -- the 6-pin PS connectors CANNOT mate with most 8-pin pin VGA power headers. Wish they'd left a little room between connectors to allow either 6 or 8-pin to be used.

-- subzero then powerup : haven't tried this trick, but Jally owners have done the "double-bag the jally, put it in the fridge for 30 minutes, take it out, power it up, and get much better hashrates" trick


I'm curious if anyone has taken the 92MM fans off the top, and just gone with the 120MM.. Fluid dynamics/vortex maybe work better?

Good informative post OP, thanks.

I swear back in June Josh swore that the Singles/Little Singles would NOT be using the low profile 92mm Fans like the Jalapenos.  I'd already purchased some nice Panaflo 92mm that i guess I won't be able to use.  That extra 10mm would've allowed for more efficient and quieter cooling.

Update in the section "Airflow / Cooling".

Update in the section "Increase of the over-all hashing rate" regarding the 25 & 50 GH singles. 

thanks for the informative post.

This thread should be a place where BFL ASIC based miners, especially their firmware and hardware should be discussed, to get a better understanding about how everything works and to find ways for improvements.

There are already some other threads, mainly focused on Jala-HW. This thread should focus on the 25/30/50/60/Minirig hardware.
Nevertheless, some of the information are also valid for other type of BFL ASIC hardware.

Latest official version, firmware version 1.2.6 => https://bitcointalksearch.org/topic/bfl-bitforce-sc-firmware-source-code-235312
My singles (60GH) have all reported on arrival to be version 1.2.6. They all had PCB Rev. D. They all where running with an over-all hashing-rate of ~60GH/s.
I've connected always two of them to a good 750W 80+gold ATX PSU, taking ~550W when mining @~25°C environment temperature.
For JTAG programming I use a JTAG ICE mkII Programmer.

Airflow / Cooling:
The units are awfully loud (fans). There are different reasons for this. One reason are the fan plates, which are really looking nicely, but are only badly doing their job to let the air flow easily and be silent. I read a lot about users which have unmounted this plates. By doing so, the whole box is getting unstable. I've also read by users who have complete unboxed the hardware. Even if the fans's could run better and more quite in a unboxed scenario I can NOT recomment it without additional cooling by e.g. additional fans. The PUSH/PULL configuration of the two 120mm fans is forcing the air to flow through the box, this includes also the backside of the PCB, which has also small heatsinks mounted, and some other hotspots on the PCB.  You can unbox it, when you know what you are doing, otherwise you are risking that some hotspots are not getting cooled enough and the unit will get defect or the lifetime is decreasing.  

I don't like the whole BFL concept to try to keep the unit cool. I would have done it completely different. However, without changing nearly everything, I would recomment at the atmost to only unmount the fan-plates, even if the whole box is getting mechanically unstable. A much better solution are improved fan-plates. I've made new ones, which are much more efficient and the fans are more silent. A friend of me has got a CAD drawing from me, and I expect tomorrow the first new fan-plates, made on a CNC machine. With this plates, you still have a stable box, are protected from touch the running fans and you have optimal air-flow inside and outside of this box/tube. It will help to keep the whole unit more quite and cool, which will be especially necessary by the next tuning steps.

The Single-SC (50/60GH) has four fans.
2 * 120mmx25mm (push/pull). I've measured a power consumption of 2.4 W @12V for this fan.
2 * 92mmx14mm on top of every heatsink (25/30GH version is only using one). I've to measure this type of fan also in the next day.
The pcb has for every fan a separate connector. Unfortunately the fans can not be controlled separately! The fan speed could be controlled in 16-steps with 4 digital outputs. This four digital outputs are controlling the output voltage of a voltage stabilizer (LM317). The LM317 is not a efficient component and therefore also wasting energy. So all fans together + LM317 are already taking up to 10 Watt.

Because of the noise users start to change fans. The default ones are really noisy, but also powerful ones. I can only warn everyone to replace the fans by other ones, if you don't really know what you are doing! The default fans have a high static pressure and airflow rate. I will look for acceptable, fan replacements which are not so noisy in the next days and will let you know.

Delivered firmware:
All my singles have reported to be firmware version 1.2.6, which is currently the latest released official firmware.
I used the connector JTAG1.
The security bit was always set, which means you can't read out the delivered FLASH (as a backup)!
One thing I've figured out is, that even if my singles all report version 1.2.6, they do NOT have the same version of firmware!
It looks like BFL is doing some kind of unit specific firmware flashing (tuning).

Therefor, if you compile and flash version 1.2.6 into your single, it COULD end up with less over-all hashing power (Hashrate minus HW-Errors) or other strange effects.
On the other side, if you know what you are doing, there is little potential to do this tuning better than BFL. I have done it, but it cost me time.

It must be quit hard for BFL to get 60GH singles out of the door, if they have to manually tune the existing firmware during production.
The 1.2.6 firmware has already included some diagnostic and tuning functions, but it doesn't yet work perfect.
Maybe this is also the reason why this products are shipping much slower than other ones.

Hashrate vs. over-all hashrate:
First some basic knowledge about the hashrate the unit is reporting.
There is a "THEORETICAL MAX" hashrate in MH/s, which could be read out by e.g. GetInfo with cgminer.
This hashrate is calculated based on how many engines are enabled in your unit, and with what clock frequency they are running.
It's mainly theoretical, because it doesn't consider the HardWare Errorrate (HW-errors), which could occur. So if you have a HW-Error rate of let's say 2% and a theoretical max hashrate of let's say 61000 MH/s, your over all hashrate is only about 59780 MH/s (devided by factor 1024 is giving you  ~58.38GH/s).

Firmware diagnostic/tuning procedure:
After powering up the firmware in every unit is doing some heavy diagnostic and tuning procedure. I try to give a quick overview about what it is doing.
Every ASIC has 16 hashing engines on chip. Something seems to be wrong with engine 0, because this engine is always disabled in the firmware (this is a another topic). So effectively you can only have up to 15 hashing engines with the latest firmware. Sometimes a part of an ASIC could have an defect, which could cause that a engine is not working or not working correctly. The firmware first tries to access every engine. If an engine could not be reached it will be disabled. Next the firmware is trying to find the best clock frequency  for every ASIC chip. All engines on one chip can only run with one common clock, but the clock can be different from chip to chip. At a specific clock frequency every engine is starting to produce more and more hw-errors. This frequency point and the hw-error rate could vary from engine to engine on the same chip, and especially also between chips. This frequency point and error rate depends also from a complex environment (temperature, voltage, etc.). So let's say from your 15 engines one engine is producing at a relatively low clock frequency already high error-rates, it could be a good decision to disable this engine completely only to be able to let the other 14 engines run at a higher frequency, which could cause an higher over-all hashing rate. So it's all about a compromise between theoretical maximum hashrate and the error-rate, and this could be influenced by how my engines you disable and with what frequency you are clocking each chip. The firmware is trying to do this. It is using test vectors and analyzes the nonce-result. All of this is done in the first seconds after power-up.
 I think this algorithms are not yet working perfectly. Two examples from my singles:
1. On one chip the firmware decided to enable all engines (15), but has found the perfect clock frequency at 0 MHz.  So the whole chip has not produced anything. The problem was only one engine, which had to be disabled.
2. On another unit there was one engine which has produced extremely high error-rates, but was not fetched by the algorithm.

Increase of the over-all hashing rate:
First, I think there is no easy thing to improve the over-all hashing rate to something like ~50-100%, like with the first Jala's.
My 60GH singles are already nearly at the limit, so it should also be with the 30GH singles. However I could increase the over-all hashing rate of my 60GH units from ~60GH/s to about ~63 GH/s with modified firmware, and I think there is some additional room left.
The 25/50GH singles have the same amount of chips mounted like the 30/60GH version. Based on the assumption that the quality of the used chips is not exaclty so much more poor, there should be more room to tune them into the 30/60GH range. I could even imagine that they are using a modified version of the firmware which is artificially limiting the over-all hashrate.

This post will be updated by myself when I've new things to report or get some feedback or information from others.