How much of a PowerSupply do i need to scale up to 4 Radeon 3850 512MBs?

kcseattle

Junior Member
Aug 2, 2008
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My mobo can scale up to 4 cards in cross fire and while only planning to add 2 Radeon 3850 512MB cards in the near term, i would like the ability to add 2 more for multi-monitor use in the future (total 8 monitors).

What level of powersupply do i need? What other cooling considerations? Thanks

Btw, the reason why i'm choosing a 3850 is primarily because of multi-monitor support (up to 8 monitors) but it seems like the most cost effectice choice (while allowing me some occasional gaming).


Thanks
 

QuixoticOne

Golden Member
Nov 4, 2005
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The total wattage isn't ALL that high, especially if your multi-monitor use is general purpose and is not
specifically for multi-monitor simultaneous high performance 3D rendering.

If you're going to frequently heavily load ALL the GPUs with 3D workloads at once, I'd be a little more concerned
about cooling and power needs.

IIRC the HD3850 boards take one 6-PIN PCIE auxiliary power connector each, so you'd need 4 of the
6 pin PCIE power connectors on your PSU, or at least 2 of the 6-pin PCIE power connectors plus four free
molex general purpose power connectors to use molex -> PCIE power conversion adaptors.

The BFG ES-800 has four PCIE 6-pin power connectors, and plenty of wattage and plenty of 12V power,
it'd be a good choice, ESPECIALLY if the promotion code is still working to give you the $90 after rebate price.
http://forums.anandtech.com/me...ht_key=y&keyword1=es-8

There have been deals in the $60-$99 range after rebates and discounts on the OCZ ProXstream 1000W unit
lately too, which isn't all that great of a unit in some respects, but I'm pretty sure it'd do the job for you in terms
of power capability. Just find out what adapters you will need to power the four 6-PIN PCIE cards as well as
your various hard drives and fans and such; you might end up needing some molex -> molex + molex splitter "Y" cables and the use of the molex -> PCIE converters and so on to get enough of the right kinds of power outputs from it.
http://forums.slickdeals.net/showthread.php?t=867620

Basically your main limit won't so much be wattage as having ENOUGH PCIE power connectors and power
connectors for all your other gear. Any good quality 700-1000 watt power supply would probably work well even
for gaming with that setup, with a good 800 - 850W unit probably being ideal.

I think I've seen various deals on other PSUs from corsair and antec and others lately, so look for something good
on sale, and read up on how many of which types of connectors you'd need.

Cooling? Get several 120mm D12SL Yate Loon Low Speed case fans from some place like jab-tech; when last
I ordered they were about $35 for TEN units total including shipping. Put them in any of the "optional" case fan
locations your case supports for good intake and exhaust airflow. Of course if your case already is fully loaded
with all the practical fans that will fit with all the GPUs installed, you may not need additional 120mm fans.

Sticking in a couple 80mm fans where they'll fit to blow on the GPUs or "slot exhaust" coolers in empty slots will
help also.

Changing out your main case 120mm EXHAUST fans for quiet but higher RPM / higher airflow units
of medium-high to high speed would be a good decision.
Ones in the 60-90 CFM range would be good, especially if you put fan controllers on them so
you can have them run slow / quiet when you're not gaming and faster when the system is heavily loaded or hot.

If you want to invest in a better case for cooling purposes, I've found some of the ROCKETFISH *full tower*
aluminium cases at Best Buy on clearance for $49 or so over the past few months. It has lots of fans built in
and it is very roomy inside which is a great help for cooling. It'd be easy to add in at least a couple of extra
internal fans too to help with the cooling airflow. If it fits your motherboard, I'd say it's a great cooling case
for the dollar if you find one on clearance sale. Otherwise shop around for other full tower sized cases.

I don't think I'd personally try to put 4 big GPUs in an Antec 900 or P180 / P182 or similar mid-tower, it'd just
be too cramped even though they do have decent cooling for their size.

Obviously you could watercool the GPUs, but I doubt it would be financially worth the cost or worth the hassle
when you can adequately cool them with just good airflow from 4-5 quality medium to high speed fans
in the case.

Reflash the bios on the 3850s if needed to enable PowerPlay power conservation so they'll run at lower
power / MHz ratings when they're under light load just acting as a 2D monitor video device. If you don't
need to reflash them to get that to work well, be sure you use the options for power conservation in
the driver / catalyst control center power profiles and in programs like ATITOOL or RIVATUNER to ensure
the fans on the cards are running at a decently high speed and the MHz is set as low as reasonable for the workload.

Look for good 800W range PSU deals on the hot deals forums of Anandtech, slickdeals, fatwallet, et. al. and
I expect you'll find a good one within 2-3 weeks if the ES-800 or OCZ 1000W sales are not still valid
or the others from corsair or whatever that I've seen in the past few weeks.
Check the PSU reviews on anandtech, legitreviews, jonnyguru site, et. al. to make sure the one you're looking
at is a good one with the right connectors.

 

kcseattle

Junior Member
Aug 2, 2008
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Quixotic, thank you for the quick and detailed response.

Here's the setup i currently have, would value your opinions:

btw, the setup was orginally intended to be a server, hence the Quad-Core Opteron processor (2.1Ghz), would I be able to set it up for multi-use, incl. potential gaming?

1) Case: Tower = Antec Go Solo
http://techgage.com/article/antec_solo/5

2) Board:
http://www.msicomputer.com/pro...K9A2_Platinum&class=mb.

3) 4GB ram


This is what I'm considering getting:

1) Radeon 2850: (2 of these)
http://www.newegg.com/Product/...x?Item=N82E16814102715 - criteria was price + single slot solution

2) In terms of PSU: Based on your reco, i'll seek out a 850 watt solution.
What do you think of this: http://www.newegg.com/Product/...x?Item=N82E16817153043

I was thinking of adding a TV tuner card too.

Do you think your fan suggestion fit within this case?
Anything else I should be thinking about?

Thanks!





 

QuixoticOne

Golden Member
Nov 4, 2005
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Here's a corsair 750W PSU with 4xPCIE 6-pin connectors
on sale $77 + shipping at provantage or $93 shipped at newegg (after rebates) :
http://www.hardforum.com/showthread.php?t=1331738
http://www.newegg.com/Product/...x?Item=N82E16817139006
http://www.provantage.com/cors...psu-750tx~7CSMC05E.htm

I'll have to look at the wattage in the reviews for the 3850's but my off the cuff estimation is that this would be quite
powerful enough to run your system with 4 GPUs.

I'm not sure you're all that likely to get quad crossfire to work well for gaming; look at some of the crossfire
performance scaling articles and you'll see that it is kind of a point of diminishing returns going from 2 to 3 cards,
and from 3 to 4 would give you even less of a linear scaling. However if you've got the GPUs that support that
it isn't a bad thing to try, but also be aware that there are bugs in the driver or some games that make even 2-card
crossfire setups not work at all or not work quite right; I assume the occasional problem cases would only get worse
with 3-card or 4-card setups. Actually I'm not even sure what documented limitations exist in the card model or
driver for 4-card CFx; I know people say it is theoretically possible but I'd confirm the details before committing to it.

The Thermaltake PSU you linked looks fine in performance specifications, but the price of $180 seems too high to me
when for well under $100 there have been several comparably good PSUs on sale lately; I'd look to spend between
$70 to $100 on a good quality 700-1000W unit unless your budget makes the decision irrelevant except in terms of
capacity/quality.

 

QuixoticOne

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Nov 4, 2005
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Here they tested a 3850 in crossfire with a QX9650 quad core CPU and a X38 motherboard and got 278 Watts
under load power consumption for the whole system in real world testing. So you could power two *entire*
crossfire *systems* (4 3850 cards total) identical to that with a good 750W PSU (2x280W = 560W), and, in fact,
if that entire power consumption was on the 12V rail it'd be only 560/12=47 Amps on 12V.
http://www.legitreviews.com/article/591/2/
http://www.legitreviews.com/article/591/13/

So a good 750W PSU will give you ample room for 4x3850 GPUs, your motherboard/CPU, some overclocking, fans,
etc. So the real limitation isn't so much having enough watts as having enough power connectors and a good quality efficient PSU.

Others have noted: "ATI was running their Spider demo machines(4 3870's) using a PC Power and Cooling 750 Silencer Crossfire Edition. They didn't seem concerned."

Here's a listing of ATI CrossFireX PSUs including some details on the number of PCIE connectors they have and the
number of cards they've been tested to run:
http://game.amd.com/us-en/cros...ex_components.aspx?p=3
Under the "3850" section you'll notice there are a couple 625 and 750W units listed with 4-PCIE connectors.
There's even a 750W unit that's certified for 4x HD4850 cards.

Here's a test with dual 3870X2 cards (quad crossfire) including a Phenom 9900 and 790FX M/B and with the
whole system peaking at 663W under load, which would be more than we'd expect for 3850s:
http://www.pcper.com/article.p...=523&type=expert&pid=8

So I'd get whatever 750+ watt PSU is attractively priced with good reviews to back up its capacity.
 

QuixoticOne

Golden Member
Nov 4, 2005
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I believe that's the power consumption of their whole PC system; it would be more consistent with the
several other power tests and specifications I've read and linked to were that the case.


Originally posted by: adlep
FYI,
The HD 3850 will go very easy on power, however if you plan on using 4 of them, you will need a 1KW power supply
According to Anand and Derek's measurements, each card needs around 186W under load, so you will need to spare 750W just for GPUs.
http://www.anandtech.com/video/showdoc.aspx?i=3151&p=11

 

QuixoticOne

Golden Member
Nov 4, 2005
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One possibility that MIGHT work if the drivers aren't buggy is to use one higher end card like
a 3870 or a 4870 for gaming and not use it in crossfire at all.
Install additionally three cheaper cards like 2400PRO or HD3450 or whatever is cheap and effective for your
multi-monitor needs. Configure the high power one as the primary GPU which would be used for
games, and all the rest as additional monitor cards, and you'd probably get a gaming performance and
reliability better than what 4x3850's in quad-CFx could deliver while preserving your multi-monitor capabilities.

Just make sure the driver doesn't have some bug where it won't let you combine those quantities and types
of cards (not in crossfire, just independent cards).
 

QuixoticOne

Golden Member
Nov 4, 2005
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I would not use the Go-Solo because it is a mid-tower sized case, and probably would be too confined due to space
limitations inside; the GPUs and their power cables would probably get in the way of your hard disc unless you
mount the hard disc up in one of the 5.25" bays with a tray 3.5" to 5.25" mounting kit.

I'd use something like this if you can find one for $49 at BestBuy or whatever.
http://www.ocforums.com/showthread.php?t=550341
http://forums.anandtech.com/me...id=40&threadid=2160785

Otherwise get a full tower from some other manufacturer that includes some extra spots for fans; personally I'd just
look on the hot deals forums and on various vendors' sites (newegg, buy.com, frys, etc.) until I saw a good one on
sale / clearance for under $100.

You could check some of the quad crossfire and quad SLI reviews on the web and see what kind of cases they've used
for their setup; the pictures will give you a nice idea of how the quad GPUs and drives and PSU fit together.

I'd look for at least two 120mm size fans in the rear, top, or side not including the PSU fan (e.g. rear + top or rear + rear or
so on).

I'd look for at least one 80mm to 120mm size intake fan in front, preferably more.

Additionally I'd put one or two fans in unused 5.25" drive bays, the kind that intake or exhaust through the front
drive panel hole. And change the main case exhaust fans to high CFM models.
 

QuixoticOne

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Nov 4, 2005
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http://forums.anandtech.com/me...=2213715&enterthread=y
2600XTs for $38.

Actually thinking about it, you should be able to use XP or Vista "hardware profiles" to help if you try to do something like install
4850 + 2600XT + 2600XT + 2600XT or similar; for gaming you can just set a profile to "disable" the 2600s or whatever if they cause a
problem, and for general use enable all of them as basic cards. Overall I'd assume you'd have better driver luck if they were all 3000
series even if the models weren't identical, though.
 

kcseattle

Junior Member
Aug 2, 2008
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Ok, you've convinced me that the 4 x 2850 route doesn't make sense since my priority is mostly multi-monitor general use and occasional gaming.

To summarize:

1 x Radeon 4850
- Diamond Multimedia Radeon HD 4850 - seems to offer the best price

3 x Radeon 2600 XT (about $30 each)
http://www.newegg.com/Product/...x?Item=N82E16814102755 - (about $30 each)

Note: I have 1 Viewsonic 28 inch LCD (primary screen) and the other monitors will be 20" or less.

Any gaming that happens will be on the 28" and obviously the 4850 will connect to the 28" LCD

Will all these cards fit on my board?
Will your recommendation of a 750 watt PSU suffice?
Thoughts on the above video cards? would you recommend alternatives?

Appreciate all the advice here. Thanks.

 

kcseattle

Junior Member
Aug 2, 2008
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I do need Dual DVI in order to get to 8 monitors but why the 3470?

Btw, in the reviews - they say it gets way hot.

Wouldn't this add to the issue if i had 3 3470s?
 

QuixoticOne

Golden Member
Nov 4, 2005
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I don't see any reason why 4 maximum size dual slot GPUs won't fit in the size of case I've suggested,
and if your board has four PCIE x16 slots spaced apart from each other by one slot in between each of
the other slots, you should be able to fit physically and electrically any GPUs you want.
I believe that is all fine based on my recollection of the picture / description of your linked motherboard when
I looked at it the other night.

The 750W PSU on sale I linked to seems like a fine choice for a 4850 + three other lesser power
consumption GPUs like 2600XTs or 3450s or whatever. If you see something similarly powerful or
slightly more powerful for a better cost of course that is fine too. Just get one with around 60A or more on
the +12V rails and four PCIE 6-pin connectors if you need that many for the GPUs you end up buying and
I'm sure it'll be fine. The one I linked is the best cost / performance deal I know about, but there have
been multiple good deals every week or two lately.

I know of no reason why you couldn't use 4850 + 2600XT (three of those) for a multi-head multi-monitor
setup that is NOT running in Crossfire mode.

I have no idea what KIND of multi-monitor setup you're trying to do; obviously having
totally independent displays with different pictures/resolutions is a little different mode than having "clone"
mode displays where they're in the same resolution displaying the same content, and those are both a little
different than having "extended desktop" mode active where the displays all form one windows desktop
that is split among the displays. So check the AMD / Catalyst / Driver documentation to ensure the
multiple displays can all run in the mode you want, in the resolution(s) you want, at the refresh rates you
want, and with the 3D/graphics/video performance you want based on your card mix.

As before I'm pretty sure you can't crossfire a 4xxx series and (either a 3xxx series or 2xxx series).
I'm pretty sure you can't crossfire a 3xxx series and 2xxx series.

AFAIK the 8.7 catalyst release for Vista 32 is the same file containing drivers for most (all?) of the
4xxx series, 3xxx series, and 2xxx series cards we've discussed, and I assume the same is true of
Vista 64 and XP packages. I can't positively tell you if there is a bug / limitation in the driver that would
prevent you using 4 GPUs of any specific type(s) or any specific model combination(s) in *non crossfire*
multi-head independent display modes for 8 displays total.
I think it should be possible, and I've heard of people doing similar things, but I don't have a way to
personally test it with any relevant GPUs. I can say there seems to be no *hardware* reason why
the proposed configurations of 4850 + 2600XT (x3) or 4850 + 3450 (x3) shouldn't work with your
4-slot PCIE x16 motherboard and a good 750W or better PSU. The only main limitations would be
whatever ATIs driver lets you to in terms of video mode / resolution and mode of the displays
(extended desktop, clone, independent), and what you're doing in 2D or 3D in your software, i.e.
do you need hardware video OVERLAY support on each of the screen, do you do 3D graphics, do you
do DX10 graphics, et. al.

People do have various bugs relating to specific display modes and operations even with *one* attached
monitor and one video card that vary from driver release and OS configuration from one month to the next,
so YMMV as to what exactly works. Vista might be more or less supportive of what you want than XP,
but I'd guess Vista ought to be better or equal; YMMV.

The one configuration that is likely to give you the fewest quirks/bugs/limits is if all the GPUs were identical
model 3xxx series or 4xxx series cards just because you wouldn't be depending on the driver to handle
the cards slightly differently though really it SHOULD JUST WORK.

For gaming though I couldn't recommend 4x 3870 or 4x 3850 or anything less; you'd get better performance
and less headaches with 1x 4850 (yes that's the best performance card for the dollar, have a couple for
that reason), or 1x 4870.

For the best performance and features (2D and 3D and high def. video playback and so on) four
identical 4870 / 4850 / 3850 / 3870 are best, but that's not very affordable for modest needs multi-head
uses except gaming, so that's why it's best to look at cheaper cards like HD2400, HD2600XT, HD3450,
or whatever you can get with two DVIs that supports your resolutions / modes / performance needs.

I'd probably give AMD/ATI support an email or call and just ask if they know of any problems mixing
a 4850 + 3x (3xxx or 2xxx) cards in one Windows Vista (or whatever you run) system NOT in
crossfire mode, just to get 8 displays to run in the ways you want. I assume they'll tell you certain
configurations definitely do work, others definitely don't work, and some are just untested but "ought to work".

I'd avoid the 2900 card unless it is REALLY cheap, it does suck a LOT of power. I'd avoid the
4870 for cost and power consumption. Anything else in the 4xxx 3xxx or 24xx or better series is probably
a good candidate to use for 2D multi-head. Your good 750W PSU should handle any combination
you pick, and a good full tower with a few fans will keep them cool enough though if you're going to
run something like folding@home or heavy 3D rendering on them all for hours a day every day I'd
definitely upgrade the cooling fan speed / quantity and be sure to run it in a room that doesn't trap
the heat.






Originally posted by: kcseattle
Ok, you've convinced me that the 4 x 2850 route doesn't make sense since my priority is mostly multi-monitor general use and occasional gaming.

To summarize:

1 x Radeon 4850
- Diamond Multimedia Radeon HD 4850 - seems to offer the best price

3 x Radeon 2600 XT (about $30 each)
http://www.newegg.com/Product/...x?Item=N82E16814102755 - (about $30 each)

Note: I have 1 Viewsonic 28 inch LCD (primary screen) and the other monitors will be 20" or less.

Any gaming that happens will be on the 28" and obviously the 4850 will connect to the 28" LCD

Will all these cards fit on my board?
Will your recommendation of a 750 watt PSU suffice?
Thoughts on the above video cards? would you recommend alternatives?

Appreciate all the advice here. Thanks.

 

QuixoticOne

Golden Member
Nov 4, 2005
1,855
0
0
OBTW about the cards fitting on your board, some of the longer GPUs can block certain motherboard
resources like SATA ports or maybe fan headers or stuff like that. Usually the GPUs *fit* fine but whatever
is underneath them can't be used; usually that is not a big problem because you can just plug things into a different
port that is not blocked by the GPU on top of it.

Usually the other problem with GPUs is they stick so far back they start to get in the way of some of the hard drive bays
on mid-tower or smaller cases; getting a full tower case or one with bays in different places solves that.

Also using some of the physically shorter GPUs helps of course, obviously a 2400PRO is a lot shorter and
usually a lot thinner than a 4870. Just download the motherboard manual for your motherboard and look at the
diagram of the connectors and slots -- assume the GPUs will go potentially all the way back to the end of the
motherboard, and take up two full slots width, so that will pretty much tell you worst case what ports are blocked
physically.

Sometimes PSU cables are a little on the short side depending on the case you use and which slots you put
things in. Unfortunately if you don't have the case and PSU and GPUs there to play with it is hard to check how well
your cables will route / fit. Worst case you usually can get a couple of extender cables if needed.