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Area 51 R4 4x GPU's?
Hi, it looks like the Area 51 R4 has enough PCIe slots for 4x 1080 Ti's, but it looks like there are only 3x PCIe power cables on the 1500w PSU. How would you power the 4th GPU? Would an adapter/splitter work? I have a client interested in a build like this.
Thanks!
Cass-Ole
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December 1st, 2017 00:00
well, the SrvcManual has the layout (left), see the separate Specs Manual (right) which explains PCI-Xpress lane assignments, they list up to triple Grfx because as you noticed the PSU only has x3 Grfx sets = 6 power cables
Y-splitter types might include dual 6's or dual 8's (eBay search term might = 8pin splitter dual)
Below, I'm not explaining this to you so much as working this out for myself, I need to see it on paper, lol
Each 6+2 (8pin) connector you have is rated for 150watts max by ATX standards, x2 available = 300w > (a 6pin is rated at 75watts)
A 375watt card, pulls 300w through the cables, 75watts through the PCI-Xpress lane itself (the gold teeth), so they say, that is because 75watts is the max PCI-X lane spec + 150 for each 8pin = 375w which complies w/ATX standards
- some manufacturers flaunt ATX standards, say a 500watt card with just dual-8pins -
A straight forward calculation suggests that card 1 card 2 receive x4 of the cables, card 3 card 4 get splitters:
Above, assumption is FE-type 8pin + 6pin Ti, now a different scenario > card 1 2 3 4 get cable 1 2 3 4, cable 5 6 = splitters
Left Image: Tri-Ti + 1080 (Ti #2 Ti #3 on paper get 225watts from cables, anything over that might trip PSU)
Right Image: dual-Ti + dual-1080
What can the side label tell us?
12V A-D 32 48 48 16 = 144a x 12v = 1728watts, yet shutdown should occur at a lower 1440watts as stated
therefore x2 48Amp Grfx rails = 96 Amps = 1152watts, it isn't as simple as expecting that shutdown happens only @1152watts+, other factors will probably not allow the Grfx to pull all 96Amps, it might depend on what 12VA 12VD are pulling at any given moment
When the Grfx push the power supply over 960watts, you're on borrowed time relative to rail 12VA 12VB, because your CPU wants to be overclocked also probably, which will trip the rail 1st, Grfx?, or CPU?
What does it look like?
It Looks Like 'Maybe'
Seek a 2nd opinion from elsewhere, join the GeForce forum, if you're after EVGA vards then try their forum etc, the side lable is there to share with people, it has a pair of 48amp Grfx rails, combined 12volt output on all four rails is 1440w max. Don't hold me to the numbers and details, they're rough guesses mostly
AfterMarket Power with plenty of cables and single 12Volt Rail?
JonnyGuru runs the top PSU website online, he works for Corsair, I explained that ax1500i won't work in Area-51 R2, he visited the Alienware factory in Taiwan or HongKong when he was on a junket, took some power supplies in, was allowed to test a few, ax1500i ax1200i Hx1200i failed to work due to a Bios timing issue measured in micro-seconds. No idea if R3 R4 have same issue or not, a person would have to try (failed compatibility is a 'click' when system turned on)
EVGA 1600, 1300 or a similar model from another brand might work. You'd buy the factory 850watt included in price (keep it or sell it) then self-install a capable supply with enough cables to power it all. If you buy the 800GY 1500watt and it fails to perform, it has re-sale value you can put towards an aftermarket type
Tell your client that the guy in the forum said 'maybe', & can not agree to anything accept that Ti + 1080 (single 8pin) looks ok, where any configuration over that ventures into the unknown due to use of splitters so you're waiting on a 2nd opinion
jk4dell
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December 1st, 2017 22:00
Thanks again Cass-Ole! I guess the max possible with stock PSU is x2 1080Ti + x2 1080s.
Cass-Ole
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December 2nd, 2017 04:00
I re-thought some things. My 1st graph was from a day ago, a day later a lightbulb went off & I made some other graphs, see my edits in the 1st post
Your basic 1080Ti (FE or entry-level card) has an 8pin + 6pin, rated at 250watts. An aftermarket card might call for 8pin 8pin (dual) in the expectation you'll overclock it or they will OC it for you (ie go over 250watts). The major portion of watts go through the cables, the rest through the PCI-Xpress lane, I don't have exact figures. In my charts, any card that surpasses 225watts through the cables puts you in the red-line, on paper at least, so to keep the power supply from shutting off / restarting with this many cards, we might try an FE type of card or a derivative of one, any card that has an 8+6
Whether 8+6 or 8+8, I'm assuming the cards won't be overclocked, in order to keep things in the red-line but not over it. If shutdowns / restarts occur, you broke the Speed Limit, you've overwhelmed the power supply > either remove overclock, remove a card, or replace power supply with aftermarket type that has more cables & a single 12volt rail
an interesting dilemma
Area-51 Grfx cables are 6+2's
*As I understand it, 75watt rated 6pin pulls 12volts from pin 1 & 3 only, pin2 simply is not used, pin 1 3 draw 37.5watts each, note there's only x2 Ground wires in the 6pin also
*For a card that has an 8pin, when you insert the 2pin section of your 6+2, the Grfx card is authorized to tap pin 1 2 3, then Ground out through x3 wires now (3 in 3 out), the wires then = 50watts each across 1 2 3 = 150watts
*Notice how if you do not insert the 2pin, the 8pin card fails to work, by design; the card assumes the power supply 12volt rail can not handle it > ie pin2 may be disabled inside the power supply, cautionary to prevent people using inferior PSU w/high power cards
What interests me about all this, is I suggested trying an 8+6 type of 'entry-level' Ti in order to keep power 'reasonable'
One graph suggests using splitters on the Ti 6pins, right? Pull 150watts through cable 5, divert 75watts to one card, 75 to other. Hmmmm. This assumes, and I make the assumption without actually knowing, that the 6pin of that 8+6 is, well, going to cheat a little bit & act like an 8pin & draw 12v across 123 & Ground out through x3. But what if it acts electrically like a true 6pin instead? That's the dilemma > example card #1 will try to pull 75watts (on paper) through your cable, card #2 will also, you'd use a splitter, but, what if that now 150watts is being called on from what we learned prior about how a 6pin behaves, it pulls 12volts only across pins 1 & 3 ... so what happens when two cards are trying to each pull 75watts (now 150watts) only through pins / wires 1 & 3? In effect we're back to the same issue as Graph #1, put the cable out of spec
for a card that's an 8+6, the above 6 > x2 6 splitter is probably best (buying an 8 > x2 8 does nothing)
On the one hand, if the card's 6pin port behaves just like an 8pin would (they've designed the 6pin to kind of cheat a little & grab up to 75watts over 3 wires as the 8pin does), then there's no issue with a splitter, but
if the 6pin port of the card is designed not to grab pin 2, & behave like a 6pin would normally behave?
what happens when two Ti 6pins try to grab 75watts over just pins 1 & 3
that's a dilemma, the splitter wires might burn up
I wish I knew, but I don't
Go back & look at the little 6pin diagram again. Now look at the Graph. Example, bottom card 1 then card 2 running off cable 5 + splitter? If those cards are an FE-type 8+6, if the 6pin is designed to only draw 12volts through pin 1 pin 3, then asking card 1 card 2 to try to pull 75watts each (150watts) just through pin 1 pin3, it looks like an overload to me
*Understand that just because cable 5 is a 6+2, and even if you buy an 8 > 2x 8 splitter (a dual 8 splitter), that's meaningless in the end if you're only using it to connect to a 6pin port
*Remember, it's when you insert the 2pin, only then is the Grfx card authorized to draw 12volts over pin 1 2 3
*In otherwords, since the 6pin port can not receive a 2pin, the 6pin might not draw from pins 1 2 3, but just pins 1 3, make sense?
But. If the 6pin port of that (8+6) Ti simply grabs 12volts over pin 1 2 3 like the 8pin port next to it does, then this is a non-issue. It's for that reason I might raise this issue in a GeForce Forum or similar > Crypto Miners & quad-SLI owners surely face these problems & may have answers on what to do, or which card is best to buy
___________________
so in a world where we never get an answer for this, what to do?
Simple
Buy the dual 8pin cards
8pins make use of all the x3 12v x3 Grounds, so, that's less stress on the splitter, but those dual-8pin cards might actually draw more power, & put you deeper into the red-line which is itself the prior dilemma which prompted me to suggest the 8+6 entry-level cards, which, might be bad in tandem with a splitter. But might not, it depends. The variables, factors & unknowns have compiled on themselves to the point I'm not comfortable in telling you any of these configurations are going to be ok or not, short of the original dual Ti dual 1080 looks ok, the rest of the configs are a step into the unknown, I don't know how to be any more clearer than that
No one at Alienware's going to authorize you to push in 4 cards with splitters I wouldn't think
The OriginPC forum? A consultation or call with them instead? They might have an opinion (=
Do not make a purchase that costs thousands of dollars based on what I said, seek a 2nd opinion
Carbon Based Lifeform
872 Posts
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December 3rd, 2017 06:00
Okay. i'm actually too lazy to type this Post....
there is NO Quad SLI Support for Pascal / Ampere Cards. 4 x HB SLI Bridges do not exist and Software Support is limited. so, even if you manage to solve the Power Issues, you'll have to use the old SLI Bridges and the Cards will only work in Quad SLI Mode with small Amount of Apps.
oh, and most of the Aftermarket 1080TI Cards are Tripple Slot Cards. your Options are pretty much limited to crappy Cards. Nvidia FE, Gigabyte 1080TI Gaming, EVGA 1080TI Black, Asus Turbo, MSI Aero, etc. are Dual Slot GPUs. good ones however will not fit.
and last Issue: imagine the Heat inside the Case.... 4 x 83 °C! good Luck with that.