So, no modified votages? Great news!
Please excuse my caution - I wouldn't like to purchase a card that will fail after a month of mining.
You might remember that the trick with unlocking shaders using a 6970 bios did rise memory voltages over their tolerances.
I'm glad you kindly sorted it all out.

MtGox, Paypal, Ebay, internet banking sites,... everywhere where money is involved, there will be criminals trying to steal it.

Kudos to OP for noting that russian domain in time.
Beware however, of more skillful attacks using less conspicuous somain names like ntgox.com, or mtqox.com.

For the sake of all legitimate users, always pay close attention to the address bar when entering your login credentials.

What a lovely handle

Jokes aside, you must have flashed the bios to allow for such low memory speeds, right?
There's no way of going that low with the stock bios from what I heard.

What I'm concerned about, is whether the bios is safe in the long run.
There have been numerous failures of reflashed 6950 cards when users tried to unlock their shaders due to increased memory voltages.
Which bios have you used? Or has there been another RBE release capable of changing mem clocks and I don't need to worry?

I'd gladly grab that card if you settled my worries about its longevity.

Also, if privacy and freedom-based arguments don't appeal to you, how about profit-based?

Quoting from https://bitcointalk.org/index.php?topic=54842.0:


How does that sound?

Yeah, BFL earned every bit of the backlash they're receiving
I'm slightly disappointed at your not being able to find the availability schedule, for it has been the most stable part of the whole enterprise for the last 2 months. It's - invariably - 4 to 6 weeks.

This is my last OT joke here. Please don't hold it against me con, I just couldn't help myself - BFL are practically begging to be ridiculed. I'll donate yet again if that will buy me your absolution

I suppose that's because unlike every other device, the BFL product is a fully professional design, built by engineers with no less than 10 years of experience under their belt.

I would also like to point out, if I may be so bold, that unlike the typical chinese sweatshops^Wfactories hastily putting together your generic USB devices en-masse, BFL (sadly no longer Inc.) have been concentrating all their efforts exclusively on the BitForce FPGA miner for the whole last quarter. Without a doubt, their corporate motto is "slowly but surely".

Try reading the BFL thread, Kano, it has all the answers  

I'd hardly call it hacked. Download the source code, change the portion responsible for tx fees, compile and viola!
Not much actual hacking involved.

They failed becuse they were all closed, PROPRIETARY solutions⁽¹⁾ fighting for "world domination". Definitely not because they were too streamlined

Bill never saw the Internet coming. To the bitter end he was leading a MSN crusade.
When they finally realized the internet was here and they don't even have a browser, they quickly (and poorly) implemented IE.


Notes:
(1)  think SolidCoin.

Well said, con.

*chanting* BFL toaster, BFL toaster, BFL toaster...
 

What you say sounds about right, P4
If the PSU doesn't feel up to snuff, OP might be getting a lot of power fluctuations resulting in a crash.

Request you post PSU specs, including the manufacturer and model info.

Paypal is great... until it orders you to destroy an antique violin
The seller remains with no money and no violin which had made it through World War II but not through a PayPal-conducted transaction (http://gizmodo.com/5872958/paypal-smashed-some-ladys-antique-violin-and-can-smash-yours-too)

Without any real competition PayPal has been known to violate its own TOS time and time again (http://en.wikipedia.org/wiki/Paypal#Criticism_and_limitations)
Let's just mention Wikileaks, Diaspora, Cryptome, or Minecraft.


Roger that, I wholeheartedly agree.

Be advised, there are some issues being reported about automatic reboot after power loss on the A870U3 (https://bitcointalk.org/index.php?topic=58441.0)

I don't own one so can't give any authoritative answer, perhaps a simple bios update would help?

Darn it, those can only be measured with an oscilloscope. I don't suppose you have one lying around?

If you have a kill-a-watt, can you measure how much power this rig is drawing? Perhaps you could buy a UPS just strong enough to to the power conditioning necessary.

Heh heh, I already gave him that advice about bitcoin.exe vs bitcoin-qt.exe I'd given you earlier today
No need to link that.

THAT. Busy-waiting is a horribly inelegant approach.

I prefer launching the X server, bitcoind, and the miners as system daemons, via init.

That requires creating files in /etc/init.d/ and running update-rc.d¹

I like to have it that way because it's a mining rig and:
(1) they are an integral part of this machine's purpose
(2) I like to be able to start/stop/restart them via the standard init commandline, eg. /etc/init.d/x-server restart or /etc/init.d/bcm² stop

Also, instead of invoking /usr/bin/X directly, I'm invoking /usr/bin/xinit

Notes:
1    You wrote "# gdm has to be stopped in /etc/init.d"
      Please be more specific: # gdm has to be stopped in /etc/init.d by issuing the command update-rc.d gdm3 disable
      The noobs are going to love having been given the proper way of disabling a daemon on a silver platter.
      If you just remove the file or deny it execute rights the next time it is upgraded it might automagically re-enable itself.

2    Obviously, bcm stands for BitCoinMiner in this context


EDIT:: Here, have a BTC-dime. Just don't spend it all at once
      

Of course they COULD. If the machine keeps totally powering down, they most likely DO.

Those are the Seasonic X-750W units, right?
If the whole rig is shutting down, it's the PSU powering the mobo that's to be blamed.
Were the other one to fail, at most you'd lose the cards it's feeding.

Make sure all connectors are firmly seated (that includes the modular cable connectors as well).
Make sure that the PSU powering the mobo is only feeding the hard drive (if any) and one GPU.
The other one should take care of the two remaining ones.

If the rig powers down again, swap the PSUs around.
If stability still isn't achieved, remove one GPU so that the PSU powering the mobo doesn't power anything else but the hard drive.

Report success here.

You don't have to do anything special with the wallet file.

However, if you have some bitcoins you're paranoid about, you could go to %appdata%\bitcoin⁽¹⁾ and manually copy the wallet.dat file somewhere (eg. to a flash drive)
Just remember to remove that copy of unencrypted wallet after you have encrypted the main one.

You don't need to do anything extra when upgrading the bitcoin client itself, just the standard housekeeping stuff: download the installer, terminate the old bitcoin client if it's running, install.
When the installation finishes, the new client will be automatically launched. It will most likely ask your permission to update the wallet to a newer specification. Agree.
When the client is done with wallet rewrite, it will close. Restart it.
Make sure you don't run the old bitcoin.exe when using a shortcut: the old client won't understand the new wallet file.

With the new client launches, click Settings -> Encrypt wallet, then follow the instructions.
From now on, you will need to input the passphrase when attempting to send bitcoins.
Everything else stays the same. The old addresses remain the same and valid. Your bitcoins are there. Earth still keeps orbiting the Sun.

Once you have encrypted the wallet, try generating a new incoming address. The client will ask for the passphrase. This way you can verify that your passphrase actually works.
Try sending a couple bitcents somewhere (you can send 0.05  BTC to the Bitcoin Faucet or to me ). You will be once again asked for the passphrase.

When you have satisfied yourself and are confident that your encrypted wallet still works as advertised, securely⁽²⁾ delete that unencrypted copy you may have made before the upgrade.
Should an adversary obtain that unencrypted copy, they can steal your bitcoins.


Having completed the upgrade and encryption parts proceed to section 3.
Truecrypt is a well-respected, free, open-source program and can be downloaded here: http://www.truecrypt.org/


Notes:
(1) Start Menu -> Run -> type %appdata%\bitcoin and hit enter
(2) Securely meaning: make sure it doesn't linger in the recycle bin.

Instead of "underground" I'd say "unprecedented".

Yeah, Intersango has had some rough time lately.
The concept of crypto-currencies has been well known and extensively discussed at academic-level. Bitcoin is the first implementation to actually gain traction in the real world.
Some banks have a hard time coming to terms with that, hence the knee-jerk reactions towards exchanges.

Until recently, the internet barely changed things for the banks and credit card institutions, merely allowing them to operate easier and faster.
They well deserve what's coming to them

It's great that you actually worry about wallet security before the worst happens. Kudos to you!
Here are my recommendations:


(0) Prerequisites: keep your machine up-to-date and malware-free!
An infected machine cannot be trusted. It can record your passphrases and send them along with the wallet file.
Never use a pirated version of an operating system! You can't be certain someone didn't add a little something extra to it.
Keeping your machine in good health is mandatory.


(1) Client upgrade technicalities.
The latest bitcoin client can be downloaded here: http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.1/
If you are currently using the old bitcoin client, chances are that the actual filename is bitcoin.exe
The new client is named bitcoin-qt.exe
Therefore, any shortcuts you might have created will have to be updated with the new name.
Installing the new client over an existing older one will not delete the old bitcoin.exe. You can remove it manually or just leave it.
Make sure you're not using the old bitcoin.exe by mistake.


(2) Wallet theft.
The new client has the option to encrypt your wallet (using the well-established AES algorithm) with passphrase of your choice. Come up with a decent passphrase, at least 16 characters long. You can use a sentence, like "The-Bad-Guys-Will-Never-Get-My-Bitcoins-Now". Don't use the example passphrase, of course

Make sure to write your passphrase down and put in in a secure place like a safe or a bank deposit box. Should you forget it, you'll want to have it somewhere.


(3) Wallet loss.
For maximum security, I suggest you create a TrueCrypt archive containing the ENCRYPTED copy of the wallet file. Don't re-use the passphrase. Keep the passphrase secure.
Once this is done, you can stop worrying about data theft and start worrying about data loss:
  +  keep an encrypted copy (a TrueCrypt archive containing the (already ancrypted with the bitcoin client) wallet inside it) of the wallet on your flash drive,
  +  copy it to your mobile phone,
  +  upload that encrypted copy to the internet (eg. mail it to yourself),
  +  if you own a file server, a NAS, or a VPC upload a copy there as well,
  +  burn it on a couple of CDs and send them to your parents, a sibling of yours, your parents-in-law...

This way, you are protected from data theft (someone obtaining the encrypted archive would have to break TWO passphrases instead of only one) and you are protected from losing the
wallet due to a hard drive failure of your house burning down.

Stay safe, stay secure, stay a happy member of the wonderful Bitcoin universe.