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Author Topic: One fast or Multiple slower GPUS?  (Read 1845 times)
Grouver (BtcBalance)
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June 16, 2011, 09:43:43 AM
 #1

Hello,

Somewhere on the forums I red that its better to have a fast GPU instead of multiple slower ones.
So the statement is as following:
You can solve blocks faster with one expensive fast GPU then with 2 slower budget GPU's while your still having the same ammount of Mhash/s?

Is anything of this true?


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film2240
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June 16, 2011, 10:46:50 AM
 #2

Hello,

Somewhere on the forums I red that its better to have a fast GPU instead of multiple slower ones.
So the statement is as following:
You can solve blocks faster with one expensive fast GPU then with 2 slower budget GPU's while your still having the same ammount of Mhash/s?

Is anything of this true?



I think that there is some grain of truth in this because of the following reasons:
1.It can be more energy efficient to run 1 super fast GPU (even if it's insanely OC'd) than running multiple slower GPUS's because a PSU can only run so many GPUS reliably without going upo in smoke or just stop working due to overloading of hte 12V rails by having several smaller GPUs rather than 1 fast one.E.g,If I put 3 HD4670 GPUS and each GPU draws 26Amps from my PSU and the PSU can only support 36Amps (when combined with 2 12V rails),the PSU would overload and fail,whereas putting in 1 meatier GPU like I dunno a Hd 5850,then I can get much more performance from the fast GPU than i ever would have by having 3 slower GPUs at the same time without risking my PSU

2.some mobos only have 2 or so PCI-E x16 slots so some cards can't be physically inside ur system due to not enough slots to put them in.

This is just my opinion on why I think it's better to have 1 fast GPU rather than 3 slower ones.I hope this helps you.If I'm wrong or missed nything out then plz feel free to add to this topic.

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June 16, 2011, 11:01:06 AM
 #3

One fast or Multiple slower GPUS?

At this difficulty? There's is the only answer: MULTIPLE FAST GPUS!

 Wink

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June 16, 2011, 11:18:11 AM
 #4

One fast or Multiple slower GPUS?

At this difficulty? There's is the only answer: MULTIPLE FAST GPUS!

 Wink

yep,It looks like mining rly is a job for multiple fast GPUs.

Also how often does the difficulty change?and why?

And how does changing difficulty affect the results I get?

I'd love 2 kno y sum ppl prefer multiple budget GPUs even tho they're not rly up to the job in the 1st place.I can only use 1 fast GPU due to PSU.Also the PSu means that I can only moderately OC it when I do get it.


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Grouver (BtcBalance)
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June 16, 2011, 11:28:30 AM
 #5

One fast or Multiple slower GPUS?

At this difficulty? There's is the only answer: MULTIPLE FAST GPUS!

 Wink
True, but still the question remains. Do you get better block solving results when having one fast GPU instead of 3 slow ones and even have the exact same MHASH/s power..

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June 16, 2011, 12:07:08 PM
 #6

The same MHash/sec = the same chance to solve block. Regardless of how many GPUs try.

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Grouver (BtcBalance)
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June 16, 2011, 03:19:15 PM
 #7

I just asked a colleague and he looks at it this way.

Multiple GPU's are more for multitasking.
And since you are not and are just calculating one type of thing he thinks you can better have one fast GPU.
Also if you run 3 tabs with 300mhash/s each isnt it just better to run 1 tab with 900 m/hash?

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June 16, 2011, 06:24:46 PM
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Think of it in simple terms:

Two groups of machines, each looking at the same block of numbers and both groups have the same rate of finding a block. 10 slow machines that each find a block every 10 seconds, so an average of one block a second, and 1 fast machine that finds a block every second.

If the block of numbers are the same, the 10 machines only have a chance to find the tenth block, as the fast machine will have found the first 9 before the 9 slower machines. The fast machine will then start to work on the 10th block at the same time the 10th machine has 1 second left of the 10 seconds to find it.

So, what does this mean?

If you have a slow machine and are solving blocks that faster machines are also solving, then you have a very reduced chance of finding a valid block.
Bitonetta
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June 16, 2011, 08:14:28 PM
 #9

In terms of Hashes they would all be the same.  But there's additional costs that some people ignore.

There's space, power and money.  If your motherboard can only hold X cards.  Naturally you are getting more MHash/sec with a high density setup.

4 Cards each doing 250MH/s will net you the same as 8 cards doing 125MH/sec. Both 1GH/sec.  But the price for all the items could be vastly different.
In the 4 card setup you may only need to buy 1 board/cpu/ram/psu.  While the 8 card you'll need to double that up.  That's $$$.  So your $/Hash just went up.

There's power.  Are the newer cards more energy efficient?  That's just math.  So the cost of 4 cards x watts compares to 8 cards x watts. (and double up board/cpu)

And finally the cost per card.  You'll get a better bang for your buck if Price/Hash is lower naturally.  There's always a premium on the newest (usually the fastest) cards.  While older hardware gets discounted.  This drought of last gen cards is usual tho.   Angry

Also, if you're going to resale after all this is done.  The newer cards should hold it's value better.
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June 17, 2011, 12:21:17 AM
 #10

Ive thought about this too.. and as far as I have figured, the problem with lots of cheap GPU's is power. A cheap GPU may get you 50MH, but pull 100W. A 5830 draws near 200W, and does 300MH. So, it's becomes much less profitable because you spend alot more on power. You also have to figure in that you can only have so many GPU's on a motherboard, I believe i read somewhere that the ATI drivers support up to 8 GPU's on a board, if you can get them all plugged in there. So that means more motherboard 'overhead' if you will.
Grouver (BtcBalance)
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June 18, 2011, 12:09:06 AM
 #11

What I mean is this..

4 x 5850 will result in about 1400 MHASH/s (4x 350 MHASH/s) and will cost you about 540 euros (4 x 130 euro)
2x 6990 will result in about 1450 MHASH/s (2x 700 MHASH/s)wich will cost you about 1100 euros (2x 550)

So why would you buy a faster GPU if you can have multiple slow ones?



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