Bitcoin Forum

Greetings,

I am using a Gigabyte 7990 (Malta) for Scrypt mining and I wanted to see what results others have had.
using CGMiner 3.2.0 with the following:
cgminer --scrypt --temp-cutoff 90 --shaders 4096 --intensity 19 -o stratum+tcp://[epools] -u [username] -p [password]
and i get 1300 Kh/s with GPU @ 1000 MHz & Mem @ 1500.
Using windows 7 currently, linux doesn't seem to have drivers available yet.

Can anyone top 1300 or help me push it a little further? Havn't been game to mess around with voltages / powertune.

Cheers

dude that is OK hashrate for that a know that 7990 i dual 7970 taxiti xt...on that clock that is best score...

nice hash speed from a single card

This card is already close to the maximum number of watts than can be handled by its VRMs and the PCI-e connectors/cables. I would not recommend increasing voltages to try and get more kh/s something will fail somewhere. Remember that in the low-voltage high-current world of GPU's even a tiny increase in voltage can result in a much increased power consumption and hence thermal output (Power = Volts*Amps). You'd be much safer with 2x 7970's.

I wasn't going to increase voltages on such a new and pricey card.
 Doesn't the 7990 use less power? Since Electricity costs are my main concern, I thought it better to go the single 7990 card even if it was more costly that 2 * 7970.

Yes it will use less power. The answer why is slightly complicated. It depends on how many power transistors are present in the VRMs of the card/card(s). Because the dual GPU cards do more with less power transistors, there is less power lost as heat in these components and so you end up with a more efficient system. Eg in dual GPU cards the ratio of power used by the cores:VRMs is higher than in two equivalent single GPU cards.

7990 is great i love it.

If Electricity costs is your main concern try to reduce the voltage even if you have to reduce the clock speed a little.

So I got a second one of these cards and can't seem to get it working properly.
After about 2 minutes of mining the rig will shut off for 5 seconds, and then reboot. It seems like a power issue but I am using a 1500W PSU and have both cards separated with 2 powered riser cables. After some playing around I found I can get the rig running only under certain settings.
I can run any 2 of the GPUs at intensity 19, enabling a 3rd will cause the reboot.
I can run any 3 of the GPUs at intensity 13, enabling the 4th will cause the reboot.
I can run all 4 GPUs at intensity 8 but its pointless.

Can anyone offer any ideas as to what is causing this?
The motherboard i am using is an Asus P7P55 LX (8gb RAM). A bios update had no effect.

What are the rest of your system's specs?

Just by the look of it, either one of the cards overheats or there is so much heat from the cards combined that they all overheat, or the powersupply just cannot keep up.

By the way, if powerconsumption is a great concern, you might want to look into GPU's that provide a better hashrate versus power used.
For instance, in bitcoin mining, three Radeon HD7750's are about as quick as one Radeon HD7950, but use about 50 tot 100watt less.

Those 7750's will draw just about 50watts and generate 130Mh/s in mining bitcoin.
A 7950 does about 450Mh/s at 300watt.
Yes, the 3x 7750 will come up 50-60Mh/s short, but uses only half the power of the 7950. Essentially it's close to twice as effective to run three 7750's.

How can I PM?

7990's have massive heat problems, as confirmed by Tom's Hardware.

http://www.tomshardware.co.uk/radeon-hd-7990-crossfire-overheat,review-32713-2.html

Two 7990's in CF are hitting 102 degrees C.

Judging by the way the cards bounce between 1GHz, 950MHz and 500MHz, it looks like the efficiency of an extra 7990 is lost in CF. It would be smarter to buy a new computer to put it in.

JM2C

Matthew:out

try running them with -i 15 sometimes you get higher #s on some cards also adding the worksize -w as 256 or 512 will make a difference to 

That is pretty good. However, in the future it might be best to mine with 7950s because they have better price/performance.

Friend of mine  just purchased 2x sapphire 7990  ( spent  1456 GPB )  mining  WDC/DGC  he got  2540KH/s
I'm using  5x7950 worth 1200 GPB  mining  scrypt coins  getting  easy  3000+ KH/s   

7990 is a pointles  idea

The 7990 is now out there for 600€, its not pointless anymore.

Meanwhile,
I have purchased some second hand 7950s from ebay which are much cheaper, run colder and almost as fast as the 7990s. The biggest problem i have had with the 7990s is the massive heat buildupm. Keeping them under 80c is a challenge, so I have had to underclock and undervolt the 7990s to best extend the life of the cards.
Im thinking watercooling is essential to get the most out of a 7990.

thanks I am going to try these settings when i get my 7990 :)

I get 1400khash on my sapphire 7990

What are your setting and driver, sdk version?   Many thanks!

Which OS and what Version of SDK? what are the settings? cheers

What motherboards are you guys using for these multi-7990 setups?