AMD 7990 - suggestions?

AgentB
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Topic 197919

I have come across a 7990 - I haven´t seen much discussion about these. I´m not sure if this is a good or bad piece of fortune.

To turn this into a cruncher I have to decide whether to upgrade my existing i5 + PCI 2.0 mobo to something better. It might be be pushing the existing Corsair 650W past it´s comfort zone...

I could

a) take out the two gtx 460s and put in the 7990
b) as a) and swap i5 for i7
c) build a new cruncher - but what spec cpu / mobo ?
d) perhaps just put the 7990 on ebay.

Thoughts?

Logforme
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AMD 7990 - suggestions?

I run a 7970 GHz edition and am very pleased with it.
Your 7990 is 2 7970 on the same board. Pro: 2 awesome GPUs, Con: They share the PCIe interface (slower transfers which hurt on E@H) and produce a lot of heat (I think AMD lowered the clocks slightly to keep it running, so low overclock headroom).
The 7970 is less neutered that most gaming GPUs and do quite well in computing. Especially in double precision projects like Milkyway@Home.

I'd go for option c, but I'm addicted to building new boxes :)
Option a should be fine, if you leave all 4 CPU cores to feed the GPUs. Don't know how much better the 7990 would be than 2xGTX460 on E@H.

Edit: Just saw that option a is PCIe 2.0. I'd go for a PCIe 3.0 board.

ExtraTerrestrial Apes
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That's a tough question. The

That's a tough question. The HD7990 is a beast and a bit dated, but: it's the same chip still used in R9 280X, the same archtitecture and the same process as AMDs current best GPUs. Something better should appear this year, but we do not yet know how much better. Your card is certainly not outdated yet and more efficient than your GTX460's.

I've just seen one being sold on Ebay for 270€. That's a nice amount of money, but could currently only buy you approximately half of your HD7990.

Regarding option b): definitely not, as the i7 would be rather old by now, the same generation of your current CPU. And you'd still be limited by PCIe 2.

How efficient is your current PSU? Of if you don't know: what's the exact type? If it's not efficient enough you'd save money by swapping it out for a new highly efficient one. And if you're upgrading anyway you could as well go for ~700 W, which would be definitly enough for that card and a small Core i3 (it's not an i5 that you have there). Although I expect your current to also handle it.

MrS

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AgentB
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Thanks for the suggestions

Thanks for the suggestions MrS and Logforme

Quote:
... And you'd still be limited by PCIe 2.

Yes MrS... which leads me to new mobo I presume.

Quote:

How efficient is your current PSU? Of if you don't know: what's the exact type?

Allegedly 80% http://www.novatech.co.uk/products/components/powersupplies/corsair/cmpsu-650txuk.html for specs.

Quote:

If it's not efficient enough you'd save money by swapping it out for a new highly efficient one. And if you're upgrading anyway you could as well go for ~700 W, which would be definitely enough for that card and a small Core i3 (it's not an i5 that you have there). Although I expect your current to also handle it.

Lorforme - what PSU, mobo do you have?

Have you measured the 7990 at the wall ?

Logforme
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RE: Lorforme - what PSU,

Quote:
Lorforme - what PSU, mobo do you have?


My 7970 is in a ASUS Z87-Pro with a i7-4770K CPU and a Corsair CX600M PSU.

Quote:
Have you measured the 7990 at the wall ?


7970, not 7990. No I have not measured the power draw.

IF you plan to run the 7990 with E@H I don't think heat and power draw will be a problem. The E@H apps don't put much strain on the GPU. During the current downtime I have switched to Milkyway@Home as a backup project and now the GPU fans are working hard, very annoying :)

ExtraTerrestrial Apes
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Yes, Einstein typically

Yes, Einstein typically doesn't tax the GPUs as hard as other projects (e.g. Milkyway, GPU-Grid) and I don't expect this to change anytime soon. I estimate your system to use about 360 +/- 40 W running only Einstein on the HD7990. This would leave your PSU fairly in the comfort zone. It's got decent efficiency of 86% / 84% at 230 V / 110 V.

Let's assume 360 W power draw at the wall in 24/7 operation. That's an energy consumption of 3156 Wh per year. If the PSU was a modern top unit hitting 93% efficiency at 230 V, power drawn from the wall would drop to 333 W. That doesn't seem much, but amounts to "only" 2918 Wh per year, i.e. savings of 238 Wh per year. In Germany this would save me about 57 €/year, so a new PSU (~100€) would pay for itself after about 2 years.

Regarding the board + CPU upgrade: well, that's going to cost quite some money. Too bad Einstein loves PCIe bandwidth, and especially so if 2 high end GPUs share a single connection. Not sure if I were ready to spend this "just for crunching". On the other hand it's not a good feeling to see such a GPU being bottlenecked.

And you wouldn't need to get an i7, especially if you don't want to crunch on the CPU. And you could also crunch Einstein on the integrated GPU of the current Intels. Usually this slows the discrete GPUs down a bit, but maybe your big bad boy will be so limited by PCIe bandwidth that this won't hurt?

You could use an MSI "Green" mainboard (saves you 6 - 10W compared to other ones) together with a Celeron G1840 (2 cores, 2.8 GHz) for 30€ or a Core i3-4160 (2 cores with HT, 3.6 GHz, more cache) for 100€ and reuse your current RAM. Or you could obviously spend more for bigger CPUs, but I don't think this is necessary since you were fine with an i3 up to now.

MrS

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Dave
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7990 takes great advantage of

7990 takes great advantage of undervolting.
I used to have one and lowered voltage from 1.2V down to 1.01V. Clocks at 1000 MHz if I remember correctly.

Power draw and temperature (therefore noise) significantly dropped as a result. I used MSI Afterburner to do that.

If undervolted 650W is plenty. Total system power back then while crunching MW @Home never exceeded 450W.
Due to high DP performance it excels at MW@Home and perf/money ratio is much better than a Titan.

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