As you can see, one is running at stock (getting about 441 GH/s usually), and the other is running overclocked (getting about 500 GH/s usually).  Both are very stable. I tend to restart the overclocked one once every 3-4 weeks or so (you'll see in the image I just restarted it, and it is still ramping up). The other one I never restart.

Make me an offer. I'll ship next day after payment is received. I kept the original packaging.

I received my B5's today (ordered July 25) via UPS.  Both are great, hashing right speeds, etc.  Except I noticed one ran hotter than the other...

The fan in the back (the one that pushes air out) never turns on.  I opened the case up - it's plugged in fine.  I tried swapping the fans to make sure one wasn't just broken - fan in the back still doesn't go.  So it isn't the fan that is broken.  Anybody have any similar issues / any ideas?

EDIT: I put the case back on and decided to let it run for a while, and the fan turned on. Lucky me. Good suggestions though. If it happens again, I'll just connect the fan directly to PSU.

Can someone explain all this talk on thermal grease? I've read a lot of this thread, but it isn't entirely clear to me.

From what I understand, you are taking off the heat sinks, adding thermal grease, and then putting them back. Why do you have to do this? It seems it makes it cooler - does that make them hash faster? Which heat sinks do you replace? Is this a problem only with Batch 1-3 or something, or would you recommend this for all of them?

I am interested in coupons as well!

I don't doubt DocNougat, but I thought I would add that I have personally had positive experiences with Minersource.net. They actually respond to support, and as long as you are courteous, I have found they will go a long way to help you out. The Black Arrow situation is very unfortunate for everyone involved, but I have received hardware from them before, and would feel comfortable and willing to purchase from them again. That said, I'm not sure I'd be willing to pre-order ANY miner from anywhere after BFL and Black Arrow.

Edit: I'm not affiliated with minersource in any way. There's just two sides to every coin, so I thought I'd provide a positive experience.

@mstrongbow, I am on the most recent 1.3.0 version. Trust me, I've been staying on top of it Definitely never seen anywhere near 5% rejects

I have also had my pi reboot 1-2 times daily. I thought it might be because of the USB hub, so I replaced it with a powered one. Interestingly, the blades seem to be running a few degrees cooler after the switch, but still rebooting. It doesn't bother me too much though - it reboots quickly, so my overall hashing power isn't affected very much.

I've got a Rk-Box, and I wanted to make sure I have done all the tricks. I have never gotten it below 10% error rates. It seems other people have higher hash rates than I do, and that's kinda frustrating. I've used rockminer's cgminer and tried their raspberry pi image, changed around frequencies, and I even replaced their USB hub with my own (no difference).  Here's what I get:

300M Freq: 456 Gh/s, 11-12% error for ~405 Gh/s poolside
320M Freq: 478 Gh/s, 17-20% error for ~395 Gh/s poolside
350M Freq: 475 Gh/s, ~14% error for ~405 Gh/s poolside

I've played with it for a week now, and haven't gotten better. Anybody with better specs have any additional tricks? Or did I just get a poorly performing box?

There are some bitcoin related papers that get published in peer reviewed sources.  Try searching for bitcoin in http://scholar.google.com.  Or even the IEEE search.  I think the best approach is to publish in locations already recognized and respected in the academic community.  Then start a new journal only once there is a a critical mass of papers are already being published in other peer reviewed sources.

Has anyone been successful in making the Rockweb Pi image wireless? The WiFi device connects and gets an IP address and everything, but for some reason if there isn't a physical cable plugged in, the thing doesn't seem to want to hash for me.

For those (like me) who purchased the Rk-box (aka Rocketbox) and are only getting 80 Gh or less from each blade, let me save you some time. As of right now, bfgminer (4.4.0) will hash slowly. You'll need to use Rockminer's customized cgminer to make it hash fast enough.  You can do it one of two ways:

1) Download (https://github.com/rockminerinc/cgminer) and on any Linux box, and compile using ./configure --enable-icarus to enable support for the rk-box. Trying to enable other ASIC types seems to make the compiling fail.

2) Download Rocketbox's custom Raspberry Pi firmware. An old one will hash slowly.  You'll have to get the most up to date one (1.2.1). An updated link should be on the first posting in this thread. Again, as of right now, Minepeon (0.2.4.6) will not work, so don't try it. I wasn't able to get the customized cgminer to compile on Minepeon either.

All told, not the most ideal situation, but that's what we have for now.  Hope this saves someone the time I took.

That could be the issue. Although I've downloaded plenty of torrents without issues.  Linux ISOs of course

As I said, the only time this ever happens is with the bitcoin client running. So obviously it's not a hardware issue.  Also, I'm not much of a programmer, but I thought in Windows, the OS is the only thing allowed to run in kernel mode, with the application using Windows API calls for kernel mode needs.  Either way, the BSOD that is happening clearly correlates to the bitcoin client, so don't tell me it's impossible for that to happen.  Maybe it's making an API call in a weird way or something.

Anybody have this problem?  I can't run my bitcoin client.  It usually takes a while (some hours), but eventually, my Windows 8 machine will suddenly blue screen.  It says the error is SYSTEM_SERVICE_EXCEPTION (ndis.sys).  That is all the detail given.  Then I have to restart my computer.  I never see the blue screen of death unless I'm running the bitcoin-qt client.

I'm running Windows 8 64-bit.  The client is bitcoin-0.8.1. I know that's one behind, but I have been trying to figure out the issue before upgrading.  The hardware is a Dell Latitude E5420.

Everyone's working on a different block because everyone has a different coinbase (the first transaction that says where to send your 25 BTC reward + transaction fees).  Plus my understanding is every miner creates their own blocks anyway, meaning they choose however many (or however few) transactions they want to stick in there - as well as which ones to put in.

Thanks Danny.  Cryptography is one of those topics that sometimes seems simple on the surface, but the further you dig, the more complicated it can get. Nice to get some answers.

This is exactly what I mean by wasted work when a block solution is found by someone else. This analogy seems better to me.  Anytime you have to change something besides the nonce in your block, you're starting over.

That clears things up for me I think.  I had thought you could just change the nonce until you eventually found the right hash (that's what I meant by checking the same block over and over - changing the nonce and nothing else).  I didn't realize you could go all the way through every possible nonce value and still not find a good hash.  Thanks!

Anybody have an answer to my last question on double hashing?

Hello
2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824 (first round on sha-256)
d7914fe546b684688bb95f4f888a92dfc680603a75f23eb823658031fff766d9 (2nd round of sha-256, from hashing the above value)

However the wiki page above says the 2nd round should yield this value:
9595c9df90075148eb06860365df33584b75bff782a510c6cd4883a419833d50

What am I doing wrong?

So in response to your answer to my question #1. Do you create an entirely new block every time you attempt to find a new, valid hash for it?  Again, that seems like a waste. If you try one hash and it doesn't work, you move on to the next because you know the old one doesn't work. So your odds improve every time - unless you change your block every time. Then it's just playing the lottery over and over again. Or maybe I'm falling for the gambler's fallacy?

So I'm seeing 2 scenarios.  Scenario 1, Slush tries to figure out the same block over and over again until BTCGuild finds the solution to a block.  Then Slush needs to grab a new set of unconfirmed transactions, update the previous block hash to the one that BTCGuild just solved, and then start over again, trying the hash over and over again.  For scenario 2, Slush forms a block, tries a hash solution, then forms a new block, tries a hash solution, etc. until he wins the lottery.  Which is it?  I just can't help but see wasted effort every time Slush has to form a new block without solving the old one.

I have several questions, but the topic is my biggest:

1) When a block is solved, does everyone else have to start over, create a new block, and begin looking for the right hash again?  For example, Slush's pool, ASICminer, and BTCGuild are all mining.  Slush solves a block, so ASICminer and BTCGuild both forget their current block, make a new one, and start over again.  Is that right? Seems a waste that way, and actually better to have 2-3 big pools rather than 30 or more smaller ones.

2) How are the transactions chosen to be put in a block? Do you just basically grab whatever transactions are floating out there that are not in a block, put them together, and start trying to find the right hash solution?

3) If you can just put any transactions you want in a block, what is the incentive to include any transaction that does not include a fee?

4) Double SHA-256 hash for hello here https://en.bitcoin.it/wiki/Protocol_specification I can't repeat.  The first round I get the same, but the 2nd round I get d7914fe546b684688bb95f4f888a92dfc680603a75f23eb823658031fff766d9 instead.  What am I doing wrong?

Thanks!  I've done some searching of the forums, wiki, etc. and haven't found those answers on my own.