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¿Low-end GPU Crossfire for Slim/HTPC?

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June 27, 2012 9:41:51 PM

Hi everyone First time-poster here. Toms forums have always given me answers, but here are some I have not found yet.

I want to build a SLIM PC that can be an all-rounder, so Im thinking in Crossfiring a pair of Low Profile HD 6570 (GDDR3) to have performance similar to an HD 6790.

So here are the rounds of questions:

1.- Is microsstutering an issue on low-end crossfire at 30-40 fps? (I ussually play at that speed)

2.- Will these two perform "better" than an HD 6770? (a friend lent me one to test)

3.- Will a generic Slim Anteck "500 Watts" PSU be able to support these to cards in crossfire?

I know they are not the best Low Profile options, but here in Mexico HD6670's LP's and HD6750 LP's are nowhere to be found, also, there are no slim PSU's i can get without paying a big premium, so I will be stuck with the PSU that comes with the case.

Thanks a lot and sorry for the long scroll.
a b U Graphics card
June 27, 2012 10:07:04 PM

Which motherboard model do you have? Make sure it supports x8 x8. Micro stuttering I random lag spikes so I think that you would notice it more.
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a c 91 U Graphics card
June 27, 2012 10:14:01 PM

Hi there, your first point is actually your biggest problem. micro stutter becomes a bigger issue the lower-end you go for cross-fire or SLI. micro stutter is an issue with dual card setups due to the way frames are rendered: through alternate frame rendering (AFR). essentially, your two video cards will alternate frames to render to give you a combined higher fps. for example, your top card will render frames 1,3,5,7,9, and the bottom card renders frames 2,4,6,8,10, to give you the full sequence of frames 1-10. you can also see here how if this is done ideally, you should get twice the performance of a single card.

micro occurs when your cards essentially hiccups, and causes instantaneous drops in FPS. the effect of these hiccups are of course more observable the lower your average fps is. if you crossfire a pair of 7970s for a 1080p monitor, you'll probably max out at 200fps most of the time, and you wouldn't notice a stutter causing a 60% frame-rate drop, since that'll only drop you down to 80fps. meanwhile, if the same thing occurred at 40fps, you'll be dipping down to 16fps, and the game becomes utterly unplayable.

can't tell you much about your other questions, sorry.
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a b U Graphics card
June 27, 2012 10:34:27 PM

I think you would be much better off using a Low-Profile 7750 like this: http://www.powercolor.com/global/products_features.asp?...

But you probably can't find that card where you are...

1) Yes: http://www.tomshardware.com/reviews/radeon-geforce-stut...

2) Meh, I haven't seen benches or tried it personally, I would think that at best you'd be near 6770 performance.

3) They really call it an "Anteck"? That's marginally clever and definitely amusing. I think even a generic 500w won't have an issue with that setup. I personally wouldn't touch it especially considering it's copying a good PSU brand-name. But if you have no other options then it'll probably do for that setup.

Again, if you can somehow find it, the 7750 LP would be preferable. Crossfiring very low-end cards is usually avoided when possible.
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June 27, 2012 10:58:34 PM

samuelspark said:
Which motherboard model do you have? Make sure it supports x8 x8. Micro stuttering I random lag spikes so I think that you would notice it more.


I have a Gigabyte GA-Z77M-D3H, but it seems to only support 16x-4x. I though bandwith wouldnt be an issue with low end cards.
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June 27, 2012 11:33:28 PM

vmem said:
Hi there, your first point is actually your biggest problem. micro stutter becomes a bigger issue the lower-end you go for cross-fire or SLI. micro stutter is an issue with dual card setups due to the way frames are rendered: through alternate frame rendering (AFR). essentially, your two video cards will alternate frames to render to give you a combined higher fps. for example, your top card will render frames 1,3,5,7,9, and the bottom card renders frames 2,4,6,8,10, to give you the full sequence of frames 1-10. you can also see here how if this is done ideally, you should get twice the performance of a single card.

micro occurs when your cards essentially hiccups, and causes instantaneous drops in FPS. the effect of these hiccups are of course more observable the lower your average fps is. if you crossfire a pair of 7970s for a 1080p monitor, you'll probably max out at 200fps most of the time, and you wouldn't notice a stutter causing a 60% frame-rate drop, since that'll only drop you down to 80fps. meanwhile, if the same thing occurred at 40fps, you'll be dipping down to 16fps, and the game becomes utterly unplayable.

can't tell you much about your other questions, sorry.


Well... thats disappointing. I tought microstutter occcured because of a variety of piled issues: bandwith being insuffient, monitors refresh rate not able to keep up, even one card waiting for the other or the cpu to respond.

With that in mind I thought these low-end (not needing huge ammounts of bandwith from the pci-e lanes) might fare better when paired with a good cpu (i5 sandy) and monitor.

And here I was thinking of a winning rig... :cry: .... thanks man
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June 27, 2012 11:47:15 PM

Larkspur

I tried to bring one of those but amazon and newegg wont ship to Mexico... even more so, I contacted directly with AFOX sales and they agreed to sell me on an individual basis, but their delivery time (4-6 weeks) and import taxes would bring it at a staggering $260 USD (thats 3600 pesos here). Thats way out of my budget.

Now, you where right, the performance is about "equal" to 6770: http://www.tomshardware.com/charts/2011-entry-level-gra...
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a b U Graphics card
June 28, 2012 12:19:33 AM

Yikes. Well, you can wait for it to become available in your country. I'm pretty sure that's as good as it gets in low-profile.

As far as micro-stutter goes - awhile back I built a new system around a i7-920 and I was waiting for Fermi (the GTX 400 series) like many other people. While waiting (entirely too long and in the end to bitter disappointment, have I mentioned that?) I snagged a deal on a couple 9600gso cards for $30 a piece. I ran them in SLI and didn't notice any microstutter whatsoever. The performance was surprisingly good but I was still turning down settings so I could still get 60fps on my monitor. I believe microstutter is most relevent under 60 frames, so if you can turn down settings to achieve this, your XFire setup might work.

My bottom line suggestion given your limitations: Don't overpay, but get your hands on a 7750 LP and in the meantime use integrated or pick up a single cheap card to get you through (maybe there's something used?).
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a c 91 U Graphics card
June 28, 2012 1:12:27 AM

larkspur said:
Yikes. Well, you can wait for it to become available in your country. I'm pretty sure that's as good as it gets in low-profile.

As far as micro-stutter goes - awhile back I built a new system around a i7-920 and I was waiting for Fermi (the GTX 400 series) like many other people. While waiting (entirely too long and in the end to bitter disappointment, have I mentioned that?) I snagged a deal on a couple 9600gso cards for $30 a piece. I ran them in SLI and didn't notice any microstutter whatsoever. The performance was surprisingly good but I was still turning down settings so I could still get 60fps on my monitor. I believe microstutter is most relevent under 60 frames, so if you can turn down settings to achieve this, your XFire setup might work.

My bottom line suggestion given your limitations: Don't overpay, but get your hands on a 7750 LP and in the meantime use integrated or pick up a single cheap card to get you through (maybe there's something used?).


actually, I just reread the opening post and realized you're building an entirely new machine... if you can hold off a little while, I would go for AMD trinity. hybrid fire it with a 6670 and it'll be amazing :) 

Larkspur, thanks for mentioning integrated graphics
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a b U Graphics card
June 28, 2012 2:12:36 AM

vmem said:
if you can hold off a little while, I would go for AMD trinity. hybrid fire it with a 6670 and it'll be amazing :) 


Yeah, great suggestion if you can wait. AMD's fusion systems are great and low-cost for slim system all-arounders. The limited benches I've seen on Trinity's dual-graphics (using a 6670) were pretty impressive.

The other thing you could do is forget slim and try using one of the non-htpc Mini-ITX cases that will allow full-sized graphics cards. That type of small-form-factor build can be very challenging though for a first-timer and doesn't always turn out to be inexpensive.
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June 28, 2012 3:57:48 AM

larkspur said:
Yeah, great suggestion if you can wait. AMD's fusion systems are great and low-cost for slim system all-arounders. The limited benches I've seen on Trinity's dual-graphics (using a 6670) were pretty impressive.

The other thing you could do is forget slim and try using one of the non-htpc Mini-ITX cases that will allow full-sized graphics cards. That type of small-form-factor build can be very challenging though for a first-timer and doesn't always turn out to be inexpensive.


Thanks to both of you, might as well wait a bit... although there are no Low Profile HD6670 here either :lol: 
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a c 91 U Graphics card
June 28, 2012 4:15:46 AM

well, it can hybrid-fire with cards a bit slower than the 6670 as well. anyway, maybe a low profile 6670 will show up when desktop trinity is released. good luck!
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June 29, 2012 1:55:40 AM

Thanks for all the feedback guys. Im trying to "click" on the "select as best answer", but it doesnt do anything. Have tried on firefox and chrome, only explorer to go...
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