Huge numbers of rejected shares on Linux with modern GPUs.

[tajjada]

Hi there,

I understand that this particular section (Newbies) is not the best place for my post, but since I am new to these forums, I am restricted to posting here.

Even though I have a fairly good understanding of the Bitcoin system, I am new to mining. I just attempted to set up my PC for Bitcoin mining, and I am getting huge numbers of rejected shares.

I am mining on 2x AMD Radeon HD 7970 GHz edition GPUs (fglrx driver version 9.012 (Catalyst 13.1)), with Phoenix2 on Linux, in BitcoinPool. I downloaded the miner yesterday and left it to mine overnight.

When I saw it this morning, it showed some scary results: 1740 Accepted shares and 1232 Rejected shares! That is over 40% of all my shares, rejected. From what I understand, such a high number of rejected shares is not normal. Is this a problem with my hardware/system? Am I doing anything wrong? Anything I can do to fix this?

My GPUs are not overclocked, only my CPU. I don't think that overclocking my CPU can affect mining results, correct me if I am wrong.

On a side note, seeing that I am using 2 very powerful cards for mining anyway, would it be better if I try mining solo rather than in a pool?

I would really appreciate it if any of the more experienced miners would be willing to help me do something about my problem. I'm willing to provide more information if I missed important details.

Thank you in advance!

[chr0me]

You're getting around 1,2gh/s aren't you?

Wouldn't really say that's fast enough to do solo mining.

[tajjada]

Yes, I am getting ~1.2GHash/s according to my miner. I really don't know how much processing power would be required to do solo mining, and that is why I asked. Thank you for clarifying this. Therefore, I made the right decision to join a mining pool.

Now, will anyone help me with my real problem, the high number of rejected shares? I really don't want to waste electricity and the life of my GPUs on bitcoin mining if 40% of my shares get rejected.

Thank you in advance!

[guille8]

Yes, I am getting ~1.2GHash/s according to my miner. I really don't know how much processing power would be required to do solo mining, and that is why I asked. Thank you for clarifying this. Therefore, I made the right decision to join a mining pool.

Now, will anyone help me with my real problem, the high number of rejected shares? I really don't want to waste electricity and the life of my GPUs on bitcoin mining if 40% of my shares get rejected.

Thank you in advance!

I see a increase on the rejected count when I'm downloading torrent (at full capacity of my crappy conection) and mining at the same time, but I'm getting only 300Mhash/s (1 HD5850).

[tajjada]

Well, the miner was the only process using the network, so there was nothing else to interfere with the miner's network access.

Since you mentioned that a low network speed can lead to increased rejected counts, could it be possible that my internet speed is limiting the miner's capabilities? I live in Africa, and only have 2mbps / 256KB/s up and down. Would you suggest I physically take this machine to some location where I could get faster internet and try mining from there to see if there is a difference?

What else could be causing the high rejected share count? Should I try a different miner, or a different kernel for phoenix2 (I tried using phatk2)? Anything I should try on the hardware, etc?

[deepceleron]

You could contact the pool admin and see if they have a log of the reject reason. There are basically two reasons for rejects:

1. You submitted work for a block number that has already been found, or
2. You submitted a hash that is invalid or below the minimum difficulty

#1 happens for everybody occasionally, a new block happens about every 10 minutes, so some miners keep working on the old block for a few seconds until they get new block information from the pool

#2 the pool might be requesting higher difficulty than 1 but your software still sends all difficulty 1 shares. You might have hardware problems that result in invalid hashes being found.

[JackPatrick]

Forget about solo mining with 1.2 Gh/s.
Try 50btc.com mining pool.
I'm using this pool right now, no rejects at all.

[tajjada]

Try 50btc.com mining pool.
I'm using this pool right now, no rejects at all.

Thank you. Apparently the problem wasn't with me or my hardware or my internet connection. There was something wrong with BitcoinPool. I joined 50BTC now and already got to 1200 shares with only 6 rejected. Problem solved. Thank you.

I can now mine in peace.  

P.S I'm never recommending BitcoinPool to anyone after this experience.