I found a very cheap fpga development board at http://www.dhgate.com/altera-fpga-cycloneii-ep2c5t144-minimum-system/p-ff80808133cfd7010133d0a6374a7d0f.html
Only $35.88 for one and even less if you buy multiple.
I'm sure it would be possible to do some bitcoin mining with it, but the speed would probably very low.
If I can get 1MH/s the thing can mine, but would be about 10 times more expensive than for example the icarus.

Thanks both

The thing I want to make is a miner.
First to test if I understand everything an unoptimized software miner, later a fpga miner.
I don't care if it is slow, it's just a hobby project at the moment.

With the links Revalin gave I found a C# implementation called bitnet.
With only a few lines of code I succeeded to get some work to do and I fully understand the data the function returns so the next step is do some hashing with the sha256 function I already made earlier.

I'm trying to find the protocol or api used by the different miners to get work from the different pools but I can't find it.
Can anyone point me in the right direction?
Soap? json? something else?

Is the price for the chip for 1 piece?
Maybe the board manufacturer gets a bulk price for buying more than 1 at a time?
Maybe the board manufacturer gets a discount for making the chip easier accessable? (I know for a fact a single chip is useless to me, with a complete board I can try to do something)

I've tried the game, nice little game :-)
But since I'm not yet seriously mining and don't want to buy bitcoins for real money (yet) I only spend 0.04 BTC and now I have 0.005 BTC left in my account.
Since you said you would loose money on the very low transactions, is there a way the cancel my account and donate this 0.005 BTC to you?
Maybe I'll play the game another time in the far future, but I really doubt I would still have my secret url to access my account.

I found it.
I made a mistake with the padding that only occurred with these 2 tests.

I've build a little C# project to try to implement SHA256 myself and tested it with test vectors from set 1 from
https://www.cosic.esat.kuleuven.be/nessie/testvectors/hash/sha/Sha-2-256.unverified.test-vectors
I used the pseudo code from http://en.wikipedia.org/wiki/SHA-2

Vector 5 and 6 fails for my program with the following output :

Test failed for string : abcdbcdecdefdefgefghfghighijhijkijkljklmklmnlmnomnopnopq
Expected hash 248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1
Result was    e9ee317b2c7807407297320147508a0e5becd7d32e27cafd66c6fd9635cc2c88
.Net version  248d6a61d20638b8e5c026930c3e6039a33ce45964ff2167f6ecedd419db06c1

Test failed for string : ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789
Expected hash db4bfcbd4da0cd85a60c3c37d3fbd8805c77f15fc6b1fdfe614ee0a7c8fdb4c0
Result was    2f3d5a2408f1a3aadc21629aaf4f261b80e0ad096214efcbf0d6ae202d39eb0b
.Net version  db4bfcbd4da0cd85a60c3c37d3fbd8805c77f15fc6b1fdfe614ee0a7c8fdb4c0

Expected hash is the hash on the website with tests, result is my own calculated hash, .net version is the hash calculated with .net's System.Security.Cryptography.SHA256.
I can find many websites that just tell me the same thing, my hash is wrong.
I've tried to find it with debugging but I really have no clue where to look since the other 7 tests run just fine.

Can anyone supply me with the w[0..63] values and the a/b/c/d/e/f/g/h values for each of the 64 loops?

I'm interested in bitcoin mining, especially in fpga mining, and I am thinking of trying to implement it myself.
I've borrowed an old xilinx spartan 3 fpga board from a friend of mine and have made a few simple small designs for it just for fun.
Now I am wondering if bitcoin mining will fitt in the board, but I don't really have an idea how big bitcoin mining will be and if it will fit in this fpga.

Selling a runescape account is not allowed : http://services.runescape.com/m=rswiki/en/Buying,_selling_or_sharing_an_account

You are going to mine bitcoins on a commodore 64 ??
How cool! 

The BTC you want to convert your currency to needs to be mined by someone who is willing to sell them to you for that price.
If the demand is growing faster than the supply the price would go up just like any other currecy or product.
If many people (more than the supply can handle) want to buy dollars, the price of a dollar goes up.
If many people (more than the supply can handle) want to buy oil, the price of oil goes up.
If many people (more than the supply can handle) want to buy toiletpaper, the price of toiletpaper goes up.
If the price of bitcoin goes up from 4 dollar to 40 dollar but you don't want to spend more than 4 dollar your waiting time is the time it takes for the BTC to drop again and reach the 4 dollar.

Hi all

I'm interested in cryptography and hashing algorithms.
I found bitcoin because a collegue told me about it.
At the moment I'm not active in mining but am interested in the fpga bitcoin mining.

You can compare it with printing money with a printer, but the printer is a very special magically printer that only prints one block of 50 bitcoin every 10 minutes.
When other people decide to use a similar printer the printer knows of the other printers and only one of them prints a new block of 50 bitcoin each 10 minutes. (on average)
You can improve the change your printer prints the next block by using a faster miner but still there's only one block each 10 minutes.

I've always been interested at cryptography and hashing algorithms.
A collegue told me about bitcoin.
At first I didn't understand the concept but now I'm thinking about trying to implement a hasher in fpga.

sometimes

You now look at the 32 byte integer as if it is a signed integer but it should be an unsigned 32 byte integer.