Shar 256 -\> Scrypt causes Hashrate to go 390Mh/s -\> 15Kh/s???

rangerk

I’m a mining newbie, so I’m hoping that I neglected something obvious and simple.

I’m using Xubuntu 12.04. I have a Raedon 7870 which I’ve been mining bitcoins with for the past couple of days. Now, I was to try Feather Coins.

I use cgminer with the following commandline:

cgminer-3.3.0-x86_64-built/cgminer --scrypt -o http://pool.d2.cc:9344 -u username.1 -p x -I 6

EDIT:

Okay, I noticed that the intensity has a big effect. I was putting it at 6. That’s what I have to do with shar256 mining because I mine while using the computer.

At I 10, I get 50 Kh/s. At I 13, I get 223 Kh/s.

Is this normal for scrypt? Can anyone suggest other tweaks?

svennand

15kh/s applies that the card drivers has crashed, or its a bad cgminer build.
Did you use prebuilt from github, or compile it yourself. if you compiled it yourself did you remember to add scrypt in the compiling.

You should se around the same hashrate with scrypt only in khash (390Mh - 390Kh)

Nutnut

First things first. Sha-256 measures speed in MHs/GHs where as scrypt is KHs/MHs. So as Svennand has stated, you should achieve ROUGHLY the same amount of KHs on scrypt as you had MHs on SHA.

Secondly, tuning of the cards is the opposite for scrypt. With sha you can underclock the video ram and simply OC the hell out of the GPU and job done. With scrypt you must oc your video ram and then balance the gpu with that. If you have simply transferred your oc setting to scrypt then that would explain the low hashes.

There are a number of guides for tuning scrypt rigs around but essentially set your clocks to standard then increase the ram speeds by 5 mhz at a time. You should see your hashes increase and then suddenly drop. Eg my 7970 does 755khs with 1500Mhz on the Video RAM but if i go to 1505Mhz it drops to ~600. So, once you have the sweet spot, do the same for the GPU.

You’ll also need to tweak the startup of cgminer with intensity, TC, LG, etc.

What’s the exact make/model of your card and what is you current startup script?

rangerk

Thanks for the replies!

svennand, I downloaded a pre-builtversion (cgminer-3.3.0-x86_64-built). Is scrypt included in the pre-builds?

Nutnut, my card is a Sapphire HD 7870. (I’m not sure what it means but also – 2G GDDR5.) I’m not sure how to check my current start-up script.

svennand

[quote name=“rangerk” post=“18518” timestamp=“1372462592”]
Thanks for the replies!

svennand, I downloaded a pre-builtversion (cgminer-3.3.0-x86_64-built). Is scrypt included in the pre-builds?

Nutnut, my card is a Sapphire HD 7870. (I’m not sure what it means but also – 2G GDDR5.) I’m not sure how to check my current start-up script.
[/quote]

yes, scrypt is included in the prebuilt version.
Try to run cgminer like this:
cgminer --scrypt --auto-gpu --auto-fan -o poolyouareusing -u username -p password

Is it still bad?