Using a PSU per "card"

[eduncan911]

Has anyone thought of using a single PSU per GPU before?

I've been trying to plan out a few mining rigs with some old mobos I have laying around, and maybe buying 1 or 2 used ones with CPUs I have.  The thing I keep running into is PSU requirements.

I am planning on 1 system to start, with the following:

HD 7990 ~550W watercooled and overclocked
HD 7990 ~550W watercooled and overclocked
R9 290x ~375W watercooled and overclocked
R9 290x ~375W watercooled and overclocked
R9 290x ~375W watercooled and overclocked
R9 290x ~375W watercooled and overclocked

That's 8 GPUs in a single rig.  The reason for the high Wattage estimate is I will be slowly watercooling some here and there, and I plan on pushing them pretty hard.  We need a heater here in upstate NY for the house. 

So the idea was to buy two EVGA SuperNOVA 1300W G2s and running 1x HD 7990 and 2x 290x per PSU.  But that's hitting right on the nose of 1300W, or more if I push things.  That is not efficient and I would prefer to stay around 80% usage of the PSU rating.

Two 1500Ws, or even the 1600Ws is possible.  But for more even $$$.  The issue I have with those setups is I highly prefer single-rail setups as I tend to, uh, really push my rigs.

But for $480 (2x EVGA 1300Ws + 1x Add2Psu), I think I can spend less if I go with a "PSU per Card" setup like this one:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817182200
^- I looked at 400-499W PSus at NewEgg, and they were more money - go figure.

So, the cost would be:

HD 7990 - 630W Single-Rail - $50
HD 7990 - 630W Single-Rail - $50
R9 290x - 630W Single-Rail - $50
R9 290x - 630W Single-Rail - $50
R9 290x - 630W Single-Rail - $50
R9 290x - 630W Single-Rail - $50

+ 5x Add2Psu ($20) for another $80.

That's $380 in power supplies and adapters.  And if one fails, I am only down a single card (would buy 1 or 2 "spares" I guess).  I also have the option to play around with what I can plug into single 15A receptacles to keep it under 1600W or so. 

That's a lot of PSUs though...


I know another option is to look at 800W or 1000W single rails for two of the 290x.  But from my research, that's coming out to be about the same cost.  Plus, a single 1000W would not handle two HD7990s.  Maybe a single-rail 1000W would handle a single HD 7990 and a single 290x, but that's exceeding the 80% efficiency rating I'm trying to stay around.

Thoughts?

[hyphenated]

Meh.

Don't get too hung up on the concept - you are adding single points of failure, making a rats nest of power cables (which probably need to be on separate rings) and generally making a rod for your back.  No-one is going to sneak up behind you and shoot you if you upgrade - start with enough for what you are going to do for the first few steps; change out if & when you blow through your margin as measured at the wall.  If you are making a heavy water investment why scrimp on the PSUs?

If you want to save, use a second-hand enterprise grade 12V 2kVA platinum slaved to a good-quality 750W and roll your own PCIe cabling.

Plus the small detail that 6 GPUs on a rig carries some fun & games in set-up (Linux only)... let alone mixing 7*** and R9 and using 7990 duals.

In your shoes I'd build a 7990 rig and an R9 rig, each with two PSUs.

[eduncan911]

Thank you for your reply.  

But actually, having a single or only 2x PSUs is a single point of failure - if the 1200 watt PSU fails, you're out 3 or 4 GPUs.  Having multiples provides the safety net that only 1 GPU will go down - not the entire rig.  Though I am sure I'd have a crash if a single PSU went out, until I found the bad one and replaced/disabled that GPU until it was replaced.

In addition, having 1 PSU each actually allows the PSUs to operate more efficiently being well under their 80% targets.

Rats nest of wires I don't see as this is the same amount of wires rather you use 1 or 6 PSUs - each GPU needs the same amount of cables to them regardless.  Sure the one I linked to isn't modular.  Just tuck the cables away next to the PSU and forget about it.  I will admit the 6x 24-pin cables could be an issue.  But in an open-air rig, that's not a problem or a concern any how.

As far as configuring 6 cards per machine, that's not a concern of this thread.    Already been done and I know what I am dealing with so it's not an issue for me.