BFL Single blowing up? Be careful with the hacks, I'll buy the blown ones. :-)

[lightfoot]

Hey everyone!

I'm Lightfoot, and I've spent the last few weeks boosting my Jalapeno from 5gh to 7.3gh to 20gh and hopefully by this weekend to 28gh. A thread on this is over here, and I'm having fun with it: https://bitcointalk.org/index.php?topic=336782.0

So I'm starting to get a good understanding of these boards. And I have a concern forming in my head for people with the Singles, specifically the 60gh ones.

Basically people have been hacking the Jallies to boost performance by overclocking. Which is fine; the Jallies were built on little_single boards and have a lot of room to play in. You can run them at higher clocks, leave dead engines online (they use full power and heat for nothing), and so forth in the quest to wring out the max hashes.

You can even be nuts like me and stick more chips on your Jally. I'm up to 5 chips now, going to 7, and I have learned a lot. You can tweak a Jally. It's fun and all that. But note this carefully, it is my opinion that:

YOU CAN'T DO THIS WITH A 30GH SINGLE OR A 60GH UNIT.

Here's my thoughts and reasons why:

The Singles appear to be similar to the little_single boards with updated FETs, more heat sinks, and of course 16 chips capacity. They both use the same 1 volt power supply to power the main part of the hashing chips, and each chip pulls 12-13 watts, which at 1 volt is 12-13 amps. Normally. When you overclock, they pull a lot more power, and I have seen this by greatly increased temps, which means more heat. Heat comes from only two places: Volcanoes under your mining rig, and the chips burning more power. It's usually the latter.

Anyway, the more power you pull, the more you stress those FETs. BFL uses 4 banks of them in a 60, each bank composing six FETs in a 3 way push/pull configuration. Overload these FETs and they will fail.

When they fail, they will fail shorted and crash your unit. I think they also blow the fuse in the power supply. Fixing this is a pain, but if you hook up a power supply without a fuse, your unit will burn the board and make smoke-like smells and boom like sounds. Board will be toast.

This failure mode is not unusual: Curtis controllers for electric cars are known for shorting the FETs and blowing up the controllers on 150 volt/600 amp systems when overloaded. Lot of boom and smoke. The fact that it's only 1 volt is irrelevant, these things are pulling 160 amps at 1 volt and that will make smokies.

This is why BFL has the code in the 1.2.8 and 1.2.9 releases that includes a DO NOT EXCEED 60gh thing. I thought it was them being a bit dick-headed, but I think the real reason is that this keeps the chips from driving the FETs into overload.

I'm seeing this on my jalapeno; every chip I add boosts the temps on my FETs. I've already got stick-on heat sinks; and I think the reason that BFL switched the board design was because a full set of 8 chips would cause the FETs to go foom too often. So they built the bigger board, balanced the load, put heat sinks and fans on those chips (explains the fans in the ends of the boxes; I have a vornado pointing at mine) and keeps the unit at 60gh.

If you go beyond, I think you are risking your unit.

So what it my unit is blown?

If you have already blown up your unit and you flashed it with hot code, I'd be willing to buy it. Now, I'm not going to start a home for wayward mining rigs, and I'm not irrational like ebay people. So I'll offer the following bitcoin formula:

Price is based on delivery 1 month hence (time for me to get it and repair) * .33% of it's total residual mining value as measured by mining.thegenesisblock.com using default values, 15c for power, 60gh for the hash rate, and 240 watts for the power use. As an example, my price right now for a 60gh, December mining date, unit would be:

.984 BTC *.33=.3276 BTC.

http://mining.thegenesisblock.com/a/17a5fd6db2

Note, I boosted the number from 20% to 33% because I believe a single/60 has a better than even chance of firing up as a 30. It is however better than nothing, and as time goes on the residual value keeps going down on these things. Ah well.

Anyway, I hope this helps people. My personal motto is "mine like hell" and I'd rather see people mining than nursing dead equipment.

C

[DrG]

There was another user I pointed in your direction who was supposedly mining at stock speeds.  My original day 1 unit only mined at 53GH/s and failed after 7 days- I had a downtime of over 2 weeks costing more than 15 BTC.

Obviously people with stock units should try to RMA back to BFL and hope they can mine a little more afterwards or find a sucker to buy the little M80s in disguise.  People with hacked 30/60s have brass balls (maybe sparky ones shortly).

[lightfoot]

There was another user I pointed in your direction who was supposedly mining at stock speeds.  My original day 1 unit only mined at 53GH/s and failed after 7 days- I had a downtime of over 2 weeks costing more than 15 BTC.

That sucks. In this game downtime is doom, which is one of the reasons I'm giving all my thoughts out for free: I could never warranty my work in a reasonable manner given the difficulty increases, and the best fix could be "lobotomize half the thing" which would upset the owner but would you rather have had 2 weeks of 30gh hashing (and 7.5btc) or 2 weeks of zilch and a 60gh system running with 2 week higher difficulty.

That's math over emotion. Bitcoin cares nothing about feelings, it's all about math and time.

Obviously people with stock units should try to RMA back to BFL and hope they can mine a little more afterwards or find a sucker to buy the little M80s in disguise.  People with hacked 30/60s have brass balls (maybe sparky ones shortly).

If the unit is stock, then BFL should replace it. They can detect the code change; they signed their code and our screwings are as obvious as a coal pile in a ballroom. If I were BFL I'd offer an immediate ship for a full charge deposit, returned when we get your unit and verify it's not custom. However in that case people here would game the shit out of BFL by using this to jump the line so that's why they can't do it. And I would be out of business because I am too much of a nice guy...

Which makes people bitch about BFL. But economically they would have no choice, see "bitcoin cares nothing about feelings..." :-)

And why I am not going to get stupid eBay-sentimental and pay anything more than what I think dead units are worth. They're dead for a reason, other people can fix them at a loss.

Honest thought here: I'm worried (why should I care? I don't know) that people have seen us jally hoppers getting 8gh out of our 5gh units and think "hey, I can do the same thing with my single 60, going from 60gh to 80-90-MORE!". But I don't think it works that way; our jallies are a unique special place and we can boost them without too much effort because they were built underpowered and overbuilt due to a unique event. BFL was totally fair to limit them to the amount we paid for, but we can take chances because they left all the FETs on the boards (probably because they were already built and such).

I believe the singles were DIFFERENT. They built them to run at 60gh, and there is not 120gh of overcapacity there. If you clock them higher there is a bigger chance that things are going to go foom. I will bet a dollar to a donut that if I put all 8 chips on my jally I will have a 50% shot of blowing the FETs within 2 weeks. I'm going to stop at 7, and heat sink the FETs and I'm watching them and not running the chips all-out.

Jallies cost us $169 which is peanuts in the grand scheme of things. People that bought a single/60 spent what $2000 for the thing? Playing mod with one of those takes balls of GOLD in my opinion. And although I have made $1000 in profit on my Sept delivery jally, I know people who bricked their units (and sent them to me to unbrick but they lost out on lower difficulty time) and would have done better to not have screwed with it without knowing what they are doing. I know what I'm doing sort of (I still bitch and whine when it doesn't WOOOOORK), I got lucky, and I have been pushing my luck to earn that money. I wouldn't do it with higher stakes.

Thus my thought of "don't dick with your single and think it's a big jally". It's not.

Ah well. This is a fun thought-experiment.

[jnoss]

You have a PM

[lightfoot]

Looking at some old BFL documents and pictures I am really ready to double-down on the whole "do not overclock your single". The power system is rated for about 100 amps over 8 chips, there is really no room for error. And I double checked some of my notes: When FETs are not all placed in the same location for heat sharing you do get the situation where the current load is split unevenly, which causes one set of FETs to get hotter and source more power till they explode.