7990 vs R290 mining

[Jamievs]

Good day folks,

Since this board appears to be for alt-coin hardware too I figured I'd ask my questions here.  I've done a lot of research and I think I just have a little too much information in my head right now to make a descision, so I figured I'd ask here.

I'm gonna build a scrypt rig (multiple GPU's) and with a good cpu for cpu mining. The choice comes down to what gpu to get. It will be a couple of 7990 or a couple of R290. 7990 shows a higher hashrate on some hardware comparison lists. Could I get some insight of people actually using those cards for mining? Are you happy with the rates and the temperatures?

Looking forward to some input since it is a tough choice for me!

[Jamievs]

Small bump since the post went to the gazillionth page already 

[sameev29]

I am guessing a 7990 itself will give higher hash rate than R9 290 or R9 290X.Although it will cost you too.

[Charles999]

7990s. you wont' like the temperature.  I constantly run above 90 c.  can be tricky to keep it running.  will burn a lot of boards.. gl

[Jamievs]

7990s. you wont' like the temperature.  I constantly run above 90 c.  can be tricky to keep it running.  will burn a lot of boards.. gl

What board? And if I keep the case open? Or the case open and extra fans on it?

@sameev29 Thanks. Height of investment is not relevant for now, ROI is

[Eastwind]

7990s. you wont' like the temperature.  I constantly run above 90 c.  can be tricky to keep it running.  will burn a lot of boards.. gl

You need to undervolt the core with MSI afterburner beta. My setting with 1.0V, 950/1000MHz, it hashes at 1320kH/s. The  temperature varies depending on the thermal paste of the cards.

[Amph]

no sense to buy a 7990

280x = 750 kh/s - 275w
7990 = 1300 kh/s - 500w

7990 = about 70% faster - about 80% consumption = fail

[kaito]

7990s. you wont' like the temperature.  I constantly run above 90 c.  can be tricky to keep it running.  will burn a lot of boards.. gl

You need to undervolt the core with MSI afterburner beta. My setting with 1.0V, 950/1000MHz, it hashes at 1320kH/s. The  temperature varies depending on the thermal paste of the cards.

I'm curious, what temps do you get?

no sense to buy a 7990

280x = 750 kh/s - 275w
7990 = 1300 kh/s - 500w

7990 = about 70% faster - about 80% consumption = fail

That's not that bad. It saves you a PCIe slot too.
It only becomes terrible if you factor in the GPU costs.

[Eastwind]

no sense to buy a 7990

280x = 750 kh/s - 275w       
7990 = 1300 kh/s - 500w

7990 = about 70% faster - about 80% consumption = fail

For me

7970 = 750 kh/s - 260w = 2.88 kH/s/W     core/memory: 1.113/1.5V, 1065/1500MHz
7990 = 1300 kh/s - 400w = 3.25 kH/s/W   core/memory: 1.0V, 950/1000MHz

So 7990 is better. We can use 4x7990 but only 7x7970 on a MB.

If we can undervolt the memory, it is even better.

The temperature I get is from 65C to 92C depending on the position of the card and quality of the GPU and how the thermal paste was applied.

Some times I have to undervolt to 0.96V so that it runs at 860/900MHz to keep temperature below 85C. I am thinking of reapplying the thermal paste, but not sure if it will void the warranty.

[Amph]

maybe you was lucky with the 7990 and not lucky with the 7970, cuz the 7990 is around 450w at least