Powered Risers are Overrated.
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Guys, honestly I think most people who decide to build over 3 GPUs machines have no idea that a 3GPU build is:
a) much easier to set up
b) cost the same as 6 GPU machine (you pay way less on PSU and MOBO - I did put everything into Excel file for proper cost analysis))
c) Does not need powered risers (even if you use 7950, it will only be drawing less than 15A through mobo, with proper undervolting, it will never go over 12A - which is the rated limited for ATX cables with two 12V cables) -
A) Not really. You’re doubling the amount of CPUs, motherboards, OSes, and other parts on a 3 GPU rig, assuming you need 6+ GPUs.
B) What motherboard and PSU did you use to factor in costs? A person with a 5-6 card rig is likely going to use a dual-PSU setup which is the same price as a 3-card setup, since you’re simply doubling the PSU price.
C) Powered risers cost about $5 more than a regular riser… So $15.
I’ve done the math quite a few times, and you’re wrong. A 6-card setup is about 7-10% cheaper than a 3-card setup. Of course, for some people, this may not be worth it, but YMMV. Going forward, I’m looking mostly at 5-card rigs, since the 6th card is usually a bit more problematic from an OS/Driver standpoint.
But by all means, give us the excel sheet, and I’ll give you mine, so we can compare notes. But on mine, I have about 1.46 KH per USD on a 3-card rig, and 1.54 KH per USD on a 6-card rig.
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I have to concure with NickCoin. Ive have several rigs ranging from 3-6 cards in em.
And by far the 3card rigs has been the most cost efficient, not to mention stable and cooler cards.
With 3 card setup you can even buy a mini-itx board with built in cpu. Then the only thing you need is some old harddrives (most have them laying around),cheap memory and a 850w cheap psu for 3x7950.
If your moving up to 4x card its an entire other ballpark, not to mentioning 5+cards, especially when it comes to psu. Last time i tried duel psu it failed horrible. Guess thats because i hotwired it and most psu needs load from other than just the 12v pcie rail…
I will be sticking with 3x cards since you can get a 80+ bronze 850w psu for around 60-70$, memory/mb/cpu cost around 150$
If you go any higher on the cards you’ll need better psus, like the Seasonic x1250 (300$), or the Enermax Revo 1500w (400$), and all you get are 1-2 extra cards, but have the issue with powered risers, more heat in a small area and so on…With an prebuilt xubuntu on a memory stick setting it up is no hassle, and with ssl connection to the headless rigs you will control em all very easily! no need to bulk to many cards in one rig!
one extra plus is if for example your away a couple of days and a rig desides to get some well deserved rest/crash, you will only lose 1800khash (3x7950), vs 2400/3000 khash if its a larger rig…
EDIT:
have to go out in the shed and fix my 4+ card rig… got the new mb and psu since the last one burned up… those pesky large rigs=P -
i have to COMPLETLY disagree! :P
disregard my previouse post
If you use 7950 cards, DO not go over 3 cards without powered risers…