So with BTC at $450, the miner price is about $1125. About the same as what Li is paying for his miners (i.e. $1150). See Group Buys for further details.

In addition to Difficulty and miner efficiency, the price of BTC has a major impact. When BTC price (as measured in USD) is high, then you get to keep more of the BTC mined after paying your electric bill. It's a complicated interplay of all those items, and they all influence the behavior of folks that are mining. The dynamics are entirely different now that BTC is roughly $440, than when BTC was $230.

Also the halving of the BTC reward for a block (down to 12.5 BTC per block). roughly in July of 2016, is starting to impact peoples decisions, both miners and vendors alike.

The last time I saw the Bitmain website, the Batch 8 page had a FIXED BTC price. In other words, it was 3.1 BTC regardless of the fiat value of those 3.1 Bitcoins. There have been times in the past on previous batches, where the USD price was fixed, and the number of BTC required for purchase was variable.

I am not sure it matters much to try and "time" when you add hash. If one entity can add enough hash to raise difficulty by 21%, I don't know if there is a lot of reason to make that two 10% steps, or a single step of 21%. BitFury can also see that Bitmain is adding hash at hefty pace via it's S7 deliveries (internal or external), so maybe there isn't much value in trying to "ramp up slowly". After all, is Bitmain going to alter their plans for S7 deliveries based on BitFury actions?

Right now, I think the "ASIC arms race" is fully underway, and it will be a while for it to "exhaust itself" to a situation like the first 6 months of 2015.  The big vendors might be VERY worried about the impact the halving will have on their ability to price miners. They might well want to transfer all that risk to their customers, and not have a lot of S7's waiting to sell in April.

For some folks, the Bitmain PSU is a non-starter, as it requires a minimum of 208V to start. Hence you can't mine with a 120V (nominal) electrical circuit if you use the Bitmain PSU.

Obviously cost, if you already have an EVGA that can be re-used for the S7.

If you are starting from scratch, there are probably better choices than the EVGA power supply, the Bitmain PSU being one of them.

OK, so I get the "BitFury testing" hypothesis. But then why did it "go away"? Unless there was some kind of huge failure, wouldn't you let it run for the most part and fix what was broken? Even if things came in too high in terms of J/GH, or maybe the immersion cooling really won't do what's expected, why not "throttle back"  in terms of frequency or whatever and still hash with what you have? I could understand testing prior to shipment of a product, but it's all internal to BitFury isn't it? It's not like ByFury has to collect a 100PH monster order and test it prior to shipment, do they?

I also take the coindesk articles with a grain of salt. They are derived entirely by what KNC or BitFury tell them. They have no way way to independently verify anything they write about KNC or BitFury, do they? We've all seen ASIC manufactures come up short on their efficiency estimates before. I see no reason to think that KNC and BitFury are immune to that possibility.

While you are trying to breathe new life into the Neptune, maybe you could find a way to add an additional PCIe jack (or something), to eliminate the overloaded 400W single power jack? My understanding is that is a common over-heat point of failure.

Just a thought from the peanut gallery. I too find these interesting. Best of luck!

This is going to be brutal!!!

+18.0 = alh

Long term, I hope my guess is wrong........

So the complete price for a single S7 is now $1150 (miner) + $100 (PSU) = $1250?

All supposed to be running by January 27th?

I think you must have the Watts and GH ratio switched. Using the 2.2 W/GH and 850 GH, that would mean a power draw of well over 1800 Watts. That just makes zero sense for an SP20. At 850 GH, what is the power draw in watts?

Is it possible that it's really 2.2 GH/W?

I am surprised if you can get 40-50KW of electricity for "free". That's quite a bit in my limited experience.

Butterfly Labs is a complete non-starter for mining gear. They haven't been viable for the last 18 months or more.

This seems like quite an undertaking as a first time mining farm. It will be at least a month before you an get the infrastructure setup and the miners delivered I'll bet. That's two difficulty increases. My expectation is that those will be at least 8% each (if not more).

You are also aware that the reward of 25BTC/block will be cut in half, roughly in June of 2016?

I had a USB based mining setup that literally ran for 5+ months without intervention. Once I ditched all the wall-warts and went to a single ATX supply with stable and adequate 5V (for the hubs and Raspberry PI), and 12V for fans and Asicminer Rbox miners it was rock steady. The other thing I attribute the stability to was the Raspberry Pi and giving up on Windows XP.  That setup just chugged right along at a steady 100+ GH, and you could always tell it was still cooking along by the blinking lights in the dark.

I never had the misfortune of owning a U3, but did have U1 and U2 miners which were rock-steady. I think the U3 was a real let-down based on the U1/U2 experience.

Sidehack's Compac fits into the rock-steady category, with stable power as well.

USB is NOT the stumbling block it might appear to be.

Actually with "free" electricity, you can just about "mine forever". Unless the 50GH runs too hot, or your "free" electricity stops, the principal ongoing cost for a miner is electricity and Internet access. Assuming the Internet is already there and paid for, you can run for quite a while. Your income will decline to a minuscule amount per month, but still positive. 

What kind of rig for 50GH, and why is the electricity "free", if you don't mind my asking?

You can most certainly mine, you just can't do so at a profit with electricity costs of $.21/KWh. If your primary motivation for mining to make money, then you'll have to host your machine somewhere else with a lower electricity cost.

Sorry, but this grows ever more common across the world. Mining will continue to migrate to areas with the lowest electric cost.

While it's possible I just missed it, "who" is making the offer? I ask primarily because there is no guarantee that they will exist in a year. They go *POOF* and you have essentially no way to collect on the guarantee.

How are you supposed to make the initial payment?

Offers that are "too good to be true", usually aren't real (i.e. a scam).

Looks to me like all of these are actually sold on Ebay.

Aye, Aye, Captain.

Add one SP20 to the pile for a bit.....

Actually it's just you. Bitmain has taken a personal dislike to you and is doing their level best to make sure you fail in the mining business. Unfortunately all the rest of us are affected too..... 

In case it wasn't obvious that was a 100% sarcastic comment and is entirely flippant in nature!!!

For virtually any other normal miner I would completely agree with you. My comment wasn't made out of random ignorance. I would swear that I read that the 21 Inc ASIC has a wallet address buried in the logic. I don't understand why, though it may all be wrapped up in some DRM scheme unique to them.

I don't think there is any reason to consider this a "normal SHA-256" mining engine. 21 Inc. doesn't sell miners in the usual sense, and hence to think we can apply our experience from others (e.g. Bitmain Avalon, BFL, etc.) is probably not right.

As I said before, if you buy into their overall scheme that's great. If not, it's probably best to move and not speculate too much on what, how, and why they did what they did. While the speculation might be fun, it's a bit pointless in my opinion.

One interesting question: Have -ck or Kano been contacted by 21 Inc? Can they say so if they have?

My recollection is that sidehack has no interest in trying to build something using the SFards chip, for a variety of reasons. I am sure he'll weigh in to correct me.