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Here is what I've done to achieve max hashrate for this GPU. I set the core voltage to 1250, and the core clock to the max of 1200Mhz. Works without crashing. Of course you'll wanna adjust the fan speed too; I personally don't mind the noise, so I have it set to 100% speed when it hits 60C.

This setting gets me 612 MH/s, with the flag "-w 64." And the temperature is the same for me, 76 - 78C while mining for a while.

So if you wanna get another 100 MH/s, this is what ya do. Cheers!

*NOOB WARNING: Do not attempt to overclock your graphics card if you don't know what your doing! It voids any warranty you have on it, and can break the card if you do it wrong.*

I have 7950s running stable at 670 mh/s (currently scrypt though). They are the new sapphire 7950s that newegg had a special on. i have 4 per rig running at this rate stable. I'll share the settings when i get home.

I have mine running at 1.238 Vcore with 1175/900 clocks. I'm using GCminer with intensity set at 10, and the latest beta drivers. I'm getting 618 mh/s steady. The only thing is, I have to go into the Catalyst control panel and set the power control to 20% for it to work at full speed

I prefer running mine at 900MHz@0,95V tbh (scrypt, can probably do 0,9V at same speed mining btc)

+1.  half the power. half the heat. half the down time.  card will live 4 times as long!!!!!

It depends on why you are mining. I'm not mining for profit at today's prices, I mine in hopes that someday they will be worth a whole lot more. When that happens I don't want to look back and think of how many more coins I missed out on to save a few bucks on my electric bills. If I were mining to sell and profit right now, then yes power efficiency would be a huge factor.

This may sound like a stupid question, but why would you buy a 7950 and underclock it so much instead of buying a cheaper card like a 7870? Also, what type of hashrate are you getting at those speeds?

Back in 2011 we had hundreds of threads on this.  Getting more hash/watt often means more density.  Instead of being able to put 300 cards in a room you can put 500.  The cards might be negligible in comparison to electricity and rent for farms

100% fan is guaranted to fuck it up very fast

Which manufacturer is the card your using for this and what the wattage use?

Life Expectancy of the FAN is always calculated at 100% as is with all fans.  Running below that line will simply extend the expected life span. I guess changing the fan on the GPU is easier than getting a new GPU  :)

Most fans will die at 100% very quickly, if you plan on running the cards for longer than 2-3 months then just don't. You will just have downtime switching out the fans and like it was said before density > max MH/card unless you have free power in unlimited amounts and don't have to worry about the heat output at all. If you are just running your gaming machines in your parents basement then sure go ahead OC that thing to hell and have it pull 350W/card. Try running 25-30 cards + at those conditions for a longer period of time and you will start running into problems.

Ive even taken my cards down to 0,875V just so I can fit 6x7950s on a single 1KW psu.

I wish LTC was nice with undervolting...

Holy crap really? Nice work.  I have to get tweaking my own it seems... Have been pretty happy just at around 590 for scrypt...seems I have some work ahead of me tonight...

edit: Please post your cooling used as well when you show the settings tonight. Thanks.

im running scrypt, cards can do about 25-50MHz higher on same voltage mining BTC but there is still a lot of room for undervolting with scrypt.

I actually do undervolt my Vapor as stock is 1.250  :o

whatever happened with voltage going down when we switched to a smaller process, 5870s were 1.15 and 5970 was even down to 1.05 at stock :p

Let me just report working settings for me on a SAPPHIRE HD7950 3G GDDR5 (using Trixx)

GPU Clock 1190
Mem clock 1040
VDDC 1.206
Board Power +20

(Sidebar Gadget reports actualy 1.125V, 62W VDDC power, 55 Amp, 59 Celcius at 78% Fan)

This is ok for 24/7 in a 20 Celcius room and gives in Bitminter around 610-615 Mhps
I can give another 10 or 20 Mhz but it becomes unstable.

PC works ok on everyday tasks.
For GPU intensive tasks (eg photoshop) I disabled the GPU hardware acceleration, so that it doesn't interfere with mining :)

let me just report settings for dual 7950 vapor-x

950core, 1250mem, 0.956volts = 1150 k/hash

415watt at wall, 170watt each card

Im getting the same 170watt per card.

Its the silly "Boost" feature I guess, the cooling on the Vapor is more than excellent. I have a "reference" 7950 Sapphire 0.981v stock and it has no problems getting to 962 while clocking the GPU at the same time..

Are you home yet?

16384 concurrency, 256worksize.
Gigabyte WF3, Voltage locked.

https://imageshack.us/scaled/large/89/680x.jpg (http://imageshack.us/photos/my-images/89/680x.jpg/)

Before anyone asks, it runs those settings 24/7. i forgot to take the SS before restarting cgminer.  ::)

wow, that is special. You are doing 680kH/s at 68C... I've got to play with my settings some more.

its a touch low.. because i just restarted cgminer, normally 71-72c.

the 6870 that sits above it isnt helping. The lone 120mm intake is underpowered (air pressure, not cfm). The case is tiny, so airflow generally sucks. Ordering a thor2 this week.

680.1k/683.2k with 339 accepted results. (vardiff bounces around the mid 200's)

what version of cgminer?

I cannot get it running on one of my rigs

some of the shell commands under win7 return no such command, and of course cgminer wont work





I have a thor as well....great case

newest. (2.11.4)

an easy way to check if the shell commands are actually working is to check your environment variables. they should show up there. make sure you put the setx in a bat file, it wont work with in with the other cgminer settings.

I actually switched over to LTC mining because I found that I can run my card at 1000/1425 with only 1.05V and still get 580 kh/s. That was with minimal tweaking so I still need to see if I can drop it more. At least now I won't have to worry about our upstairs being 100F in the summer.

What about clock speeds?

/points to the green box in the screenshot.

Help me out here. I have read every thread on litecoin mining and the 7950 gpu.

I have a msi 7950 twin frozr. I can not get above 8129 threads. I tried the GPU_MAX_ALLOC command, but it did not do anything for me. Right now I have to run 2 gpu threads and I am getting around 550 kh/s, but I feel like I can get a lot more out of this card. Has anyone fixed this problem? I searched the board and it seems some people have this prob others don't.

i too can't seem to get scrypt mining to work properly with my new Gigabyte 7950s

I've read elsewhere that the current (and beta 13.3) drivers under linux weren't as optimized for use in scrypt mining as windows' are - so tomorrow I'll be trying out a ssd boot disk with 64bit win7 on it and see if I can't get cgminer to give me those elusive 600+ khash. 

Anytime I get cgminer to run > 300k scrypt on a card, it gives massive amounts of hw errors.  When I use suggested values I've found here (and elsewhere) no joy, i can't see to get tc > 8192 to really work.

Are people getting > 600khash on 7950s in any o/s other than windows?  if so: what o/s, driver, sdk and cgminer versions plz thankuverymuch!

holy variable-soup, Batman!

Johnny5, I'm running:
Ubuntu 12.10 (kernel 3.5)
13.1 drivers
cgminer 2.11.4

I'm currently getting 620 Kh/s, standard voltage. 1050eng/1500mem/19intensity.
currently trying the settings shown in the images above (1110eng/1500mem), getting about 650, watching stability.

Also curious to see how 12.8 or 12.10 drivers do.

I'm sure you meant 8192.
did you verify the command worked, and is spelled right?
(if you're on windows, check your environment variables. right click my computer, advanced system settings, environment variables, it should show up in the top pane.)

AFAIK, the difference in threads makes no tangible difference in most cases...and i have yet to get a card to work above 10240 concurrency with 2 threads... not that i need to, 1 or 2 threads at 8192 gives me the same speeds.

I ran 12.10 for a long time, despite everyone (and tacotime) saying it was bad for LTC mining. I run 12.8 on both boxes, and whatever SDK came with it.

One thing i DID notice recently, the High intensities don't play well FOR ME with lower work sizes. 64/128 at any intensity >13 gave me 50-60kh/s lower than 256 work size.

As always YMMV.

Edit : Sorry coingarbler, i dont dabble in linux.

The card above (locked wf3 1x 6 pin and 1x 8 pin connector) runs the 1100/1500 24/7. i just had it at 1110 cause i was inching it up 5mhz at a time to find the max (1125 @ stock 1.25v) im not raising the voltage just due to the lack of cooling explained above.
My other 7950 (unlocked gigabyte wf3, 2x 6pin connectors) runs with all the same cgminer settings, same driver version/sdk, same everything in cgminer, and gets 630kh/s at 1050/1750 at 19 intensity.

Go figure.

I checked the environmental variables and the 100 gpu thing is there. But I still can not go above 8192 threads. This thing is driving me nuts.

i have my 7870 tahiti le   which is basically a 7900 chip...   setting worksize from 128 to 256 greatly increased my hash rate per second.  I would say the increase was by about 10% give or take.  Went from 450 to 505-512mh/s

Tried out Rjb82's settings with 13.1 drivers on ubuntu linux 12.10, doing 1100eng/1500mem/20intensity, working well at 648 Kh/s on SAPPHIRE Vapor-X 100352VXSR cards.
Not to hot except for one which has riser cables in the way in my rat's nest ghetto milk crate build.
Thanks Rjb!

If anyone's on linux, here's some settings that worked well for me:
(warning, unix nerdery below)

1. create a bash script , i.e. run_cgminer.sh

#!/usr/bin/env bash
export DISPLAY=:0
export GPU_MAX_ALLOC_PERCENT=100
export GPU_USE_SYNC_OBJECTS=1
export GPU_MAX_HEAP_SIZE=100
cgminer --scrypt -c $1 ${@:2}

2. I then put the config details into a JSON-formatted .conf file, such as:

{
"gpu-engine" : "1100",
"gpu-memclock" : "1500",
"intensity" : "20",
"thread_concurrency" : "16384",
"vectors" : "1",
"worksize" : "256",
"lookup-gap" : "2",
"temp-target" : "70",
"auto-fan" : true,
"scrypt" : true,
"pools" : [
   { "url" : "stratum+tcp://luserpool.com:3333",
     "user" : "LTC4CO2",
     "pass" : "LTC4CO2"
   }
]
}

3. then I call run_cgminer.sh (don't forget to make it executable with %chmod +x run_cgminer.sh) with the .conf file as an argument, and any arguments I want to add:

%run_cgminer.sh somefile.conf [ extra arguments ]

4. actually it's nice to use a program like 'screen' to keep your terminal session alive even if you log out / get disconnected. Screen is like a terminal server
a - ssh in
b: %screen -R -D cgminer_session
c: start cgminer script
d: detach from cgminer session with ctrl-A, d
later on ssh in again, re-attach to cgminer session with %screen -R -D cgminer_session

5. getting cgminer to start automatically on boot is left as an exercise for the reader. Note, you must have an X session running.

6. bonus points for automatically rebooting when GPUs lock up.

Which seems to get the highest speeds between sapphire and Gigabyte?  I'm looking into buying a few.

I spent a few hours trying to get CGMiner working for LTC mining, but gave up because no matter what I tried it would reject my shares. I am now on the latest guiminer running with the 7950 high usage preset, intensity at 19, clocks at 1050/1525 @1.125V. I'm getting 625kh/s with around 0.8% rejected/stale shares. 

what version of the miner do you have? can you post link thanks. The newest one i downloaded didnt have any presets.

I have same cards please post settings

Has anyone solved the whole issue of card not being able to go above 8192 threads. I am using drivers 13.1 drivers.

I'll post it later tonight.

Here is the link

https://bitcointalk.org/index.php?topic=150331.0 (https://bitcointalk.org/index.php?topic=150331.0)

Ok yeah ive used that one before thanks. i just got everything to work with cgiminer now, i might try guiminer in the future

setx GPU_MAX_ALLOC_PERCENT 100   type that into command prompt make sure its in caps! Or it will not work

I already solved it, it was a not enough ram on the system.

Thanks for the info. I'm expecting my order of 3x 7950s tomorrow and I'll try these settings.

Incredibly sorry i never replied. I totally forgot about this thread until a user just PM'd me.

here's my settings.