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I have tested all kinds of configurations and finally the highest hashrate I can get out of my 7950 cards (with stability) is 630 KH/s. I have seen people reporting hashrates of over 700KH but I just can't imagine how to get there at this point.

Currently the cards are configured as follows:
Intensity: 20
Powertune: 18
Memory freq: 1575
Engine freq: 1110
VDDC: 1.1 V

With these parameters I have the cards running stable at around 72°C. If I increase the engine frequency I might get a few more KH (not so many) but eventually the whole system hangs up or one of the cards appears as "DEAD" on cgminer. I have also tested a very wide range of different frequencies for memory and GPU engine but this is the best hashrate I have achieved.

Crank up the voltage. Keep an eye on the temperatures, though.

EDIT: And like ymer said, those values are actually quite good. You could squeeze out more with higher voltages, but it will screw up the efficiency (MHash/J).

630KH is very good IMO, I can't get more than 575 out of my 7950

thats my upper limit on my MSI 7950.  usually i run it at 550-580khash fan @ 69-71% and temp 70*c

i spent countless hours tweaking my HIS 7950 to finally get ~645kh/s @ 1.031v and 1.525v mem, very happy with performance per watt

at first i could hardly get it to 550kh/s

these bastards are finicky, but what helped for me was bumping thread concurrency to 22400+ (HW errors galore below that) with 1500mhz mem clock and 1050mhz processor

that got me to just under 600, and tweaking intensity, tc and frequencies in small increments would find me 10 or so kh/s here or there, until i apparently found its sweet spot

also, using the VBE7 tool to disable boost and set the stock voltage to 1.081 in firmware helped with stability big time, and allowed me to set powertune to -20% instead of +20%

currently i do
tc: 24000
engine: 1139
mem: 1500
intensity: 19


19 and 20 intensity doesn't give me a hashing difference, but i get nearly 2% rejected with 20 vs .05% with 19


also, i realized my card is basically worthless for actually connecting a display--colors were off (over saturated-- didn't realize until i upgraded to a 280x) and it crashed all over the place when starting/stopping the miner

i was pissed when i used the card for playing games--very unhappy with 7950s for gaming in general (artifacts every now and then even at stock speeds, that boost nonsense is complete shit)


not sure how much of this applies to sapphire's, but when tweaking i had the most luck with mimicking what sapphire owners did compared to other brands, so i imagine they're fairly similar

Draino, someone mentioned latest catalyst drivers reduce artifacts. I used to get tons with high intensity, and now i just get some screen lag.  may be worth investigating.  I get stuck at -10% power, cant reduce more.  anything lower than -12% drops my hash rate by 150-200k

luckily i added a card that has 2 display ports so i don't even have to worry about it anymore, i can just let the 7950 do its thing and warm up my room during this arctic vortex haha

Around here, its minus 20c outside, i do an average of 670kh/s per 7950 at 50c. I did a complete ventilation system, where the outside air is brought underneath the rig and have a powerful fan both in and out. The out ventilation is at the top of the ceiling. I found that the coldest the cards are, more accepted shares are provided. Temperature management is key in mining, especially when you gain this much more. It might not be much but for each card, at the end, it shows.

man, i hear about the cold climate miners, and i have to wonder if there wouldn't be some effecient way to harness that heat instead of just pumping it outdoors

although i suppose getting the miners cold and recycling heated air are entirely opposing

I'm curious to see what does your .bat file look like? Thread concurrency specified and other settings?

Donatel do you worry about moisture using outside air?

Also open ended question or statement... Using GPUid or whatever program I can see GPU memory being used dynamic&dedicated.  I don't have the numbers in front of me but higher thread concurrency only increased the video card ram usage. It never really affected my khash output tested concurrences ranging around 8000, 24000, and 30000. 8000 used 1.2-1.5gb, 30000 used just under my card 3gb total

Me same. Radeons are expensive.  Rather them run longer life

I only get 500-530 WU out of my Sapphire Vapor X 7950's, Sapphire Dual X R9-280x around 600-630 WU, stable indefinitely. Apart from overvolting I don't know how people get them to go higher.

I got what I could out of stock voltage then undervolted while maintaining stability and WU.

Initially I was running at higher voltage (no undervolting). The hashrate was more or les the same but the cards became extremely hot (one got up to 90° with fans at max speed)

My TC is also 24000 (forgot to mention), I also had tons of HW errors if I set it lower. If I reduce powertune the hashrate falls dramatically (385K at -18). Will try with I=19 though to see if I get less rejections.

It looks like this:

setx GPU_MAX_ALLOC_PERCENT 100
setx GPU-USE_SYNC_OBJECTS 1
cgminer --scrypt -o stratum+tcp://middlecoin.com:3333 -u XXX -p x -I 20 --gpu-engine 1110 --gpu-memclock 1575 --gpu-powertune 18 -w 256 -g 1 --lookup-gap 2 --thread-concurrency 24000

Generally I also end up setting the fans to a fixed speed (75% to 85% depending on the weather) so the temp is stable

Yes that's completely true. I have a pretty good ratio IMO (average WU around 580 and no HW errors). I will have a deeper look at the readme, thanks for the tip!

Running a sapphire 7950 myself here are the paramters:

#!/bin/sh

export DISPLAY=:0

export GPU_MAX_ALLOC_PERCENT=100

export GPU_USE_SYNC_OBJECTS=1

cd /home/xxx/Desktop/miner/cgminer-3.7.2-x86_64-built

./cgminer --scrypt -o stratum+tcp://eac.poolerino.com:3334 -u deltree86.1 -p 1 --thread-concurrency 21712 -I 19 -w 256 -g 1 --gpu-engine 1100 --gpu-fan 50-100 --gpu-memclock 1520 --gpu-powertune 20 --temp-cutoff 95 --temp-overheat 80 --temp-target 70

This is most stable and devoid of too many rejects and 0 hw errors. Hashes= 636 Getting 72c degrees myself in a open no case environment.

it depends on brand and chip quality also.

changing scan time and expiry may also help with WU (saw it suggested on middlecoin thread and it does seem to make a bit of difference)

i have mine set to 1 each

frankly, what the pool says i'm getting for hashes always seemed to match up in a decent range with what cgminer reports for hashrate, regardless of the ever fluctuating WU, so i don't pay much attention to it

i might be alarmed if it was 50% of my hashrate or something like that

Scan time messed me up starting a few new alts at launch time.  If it's set to 60 a hundred blocks could be solved in that first minute!  Not sure how expiry helps guess I need to read more.  I set scan to 1 for launch then 5-20 depending on difficulty.