Difficulty will be 164 000 000 starting from a 216 000 difficulty,  (next estimate)

given 7 block/hrs, a 16% increase for 43 generation for 756 times the difficulty.

I don't know much about this stuff, but based on the fact that a 5870 can get up to 2.7 Teraflops, that would make the government computer 370,370 times faster.  I hear that 5870s get about 300 Mega hash/s so that means that the Exaflop computer would get like 111 MILLION Mega hash/s or 111 Tera hash/s.  That's a block every 59 minutes on average, at the current difficulty level.  Did I do my math right?

The average time to generate a block at 111000000000 Khps, given current difficulty of 109670.13329248 , is 4 seconds

I worry that the difficulty level will increase to such a point BEFORE this project even gets started that it will make the whole venture uneconomical. Remember that you're chasing a MOVING target - the difficulty level. At some point the amount of money the investor will be making from his share of the rigs won't be enough to cover the cost of the administrative fees or whatever he will be charging.

This is the same scenario with minim on our own (non cluster) except if we do this on our own eventually down the road when the difficulty level is too high to keep our rigs mining we can just SELL our rigs and get some cash back. I don't know how we'd have that option in a mining cluster. I suppose we can sell our shares on the newly proposed stock market, but umm what if nobody wants to buy your shares - and you can bet they will not if they know that it will cost them more in electricity/administrative fees then they get back in BTC.

Please don't misunderstand me as trying to throw a "money wrench" in this venture. It's just that there are a few unanswered questions that need to be addressed.

Hello,
It's an interesting idea but how would you create your ownership structure?
Questions:
Would you form a private corporation to own the hardware, do GAAP accounting and provide that to shareholders?

Would an investment in the project result in a purchase of shares in said corporation? If not or if the rights are nonvoting, how do you propose to protect investors against fraud.

When the hardware is sold for whatever reason, would that capital be returned to investors. This is not an issue if your investors have voting rights in a corporation because they could force it at that point.

I ask about all this as your post said it was seeking investors rather than purchasers of mining contracts. So, if I invest, I want a slice of the hardware, say over management, fees etc, and how the system is run in proportion to the BTC I invest.

If you're really serious about a cluster, you should use a PCIe expansion chassis designed for GPUs, which can hold 16 cards rather than a bunch of separate computers.  For example, the Dell PowerEdge C410x.  It works with ATI/AMD cards as well as NVIDIA cards, and can plug right into any computer to add 16 PCIe slots.  In a 42U rack you can easily fit three computers, nine of those, and a power distribution unit and you'll find yourself with 144 6990's--which is somewhere around 100 billion hashes per second.  All for a cost of under 140 000 BTC.

We will be launching a bitcoin stock exchange in less than 2 weeks, you can use this to get your capital if you can wait. It will seriously cut down on administration with investors and remove the need for a minimum investment.

I may be interested but this is your first post it would be foolish to send a non revocable payment.  What assurances could you provide?

Do you remember about difficulty adjustments ?

Hmm, may be I should offer such mining contracts too... ))