7850/7870 performance

Concillian

Diamond Member
May 26, 2004
3,751
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We don't know for sure at this point, and we won't until the NDA is up and the cards released but it's looking likely that:
- both at stock clocks the 7850 will likely be slightly slower or about the same speed as 6950, but lower power consumption.
- Overclocked, the 7850 will likely have significantly more OC margin and end up faster than an OCed 6950.
 

superjim

Senior member
Jan 3, 2012
293
3
81
We don't know for sure at this point, and we won't until the NDA is up and the cards released but it's looking likely that:
- both at stock clocks the 7850 will likely be slightly slower or about the same speed as 6950, but lower power consumption.
- Overclocked, the 7850 will likely have significantly more OC margin and end up faster than an OCed 6950.

Let's not forget that most 6950's can be unlocked and are essentially 6970's in sheep's clothing. It will be interesting to see OC comparisons for these 2 cards.
 

Mopetar

Diamond Member
Jan 31, 2011
8,010
6,454
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Performance is said to be somewhere between the 4870 and 7970

We've also just confirmed that the price will be somewhere between a Tootsie Roll and a Cadillac, and some sources are claiming that power usage will fall between a light bulb and a Hummer. More information to follow as additional details emerge.
 

Concillian

Diamond Member
May 26, 2004
3,751
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Let's not forget that most 6950's can be unlocked and are essentially 6970's in sheep's clothing. It will be interesting to see OC comparisons for these 2 cards.

I'm not forgetting that.
6950 unlock does nothing for ROPs. ROPs are all clock speeds. ROPs have also shown to be a big driver in overall performance in AMD's architecture. Bigger than shaders and bandwidth.

This means clocks rule, and 7850 OCs will be purely from the clocks. Even if shader OC will be similar between 6950 typical OC + unlock and 7850 typical OC the 7850 will have a better ROP OC.

OC comparisons will definitely be interesting. Don't know how many people with a 6950 would bother with one of these cards though, as it would be a pretty small change in performance for $250+ in a more 'value' oriented segment than the 580 / 7950 / 7970 market segment.
 
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Borealis7

Platinum Member
Oct 19, 2006
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it should perform like a 6950, but have big overclock headroom in addition.
the 7 series just begs for overclocking, but O/Ced power consumption may be prohibiting to some users.
 
Sep 19, 2009
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Playing unscientifically with some numbers, using a 1280SPs Pitcairn @ 1GHz, I think it should be about 30% faster than Barts, what sounds quite reasonable.
(Although up to 40~45% faster wouldn't be far etched, depending on the memory's clocks and at what point the GCN's shaders scaling goes downhill)
 

FalseChristian

Diamond Member
Jan 7, 2002
3,322
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71
Stick with your 6950. Why do a sideways 'upgrade'? Yer good until the HD 8970 is out later this year.
 
May 13, 2009
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After seeing 79XX and 77XX series pricing I just said a prayer over my GTX 480 in hopes that it lasts for another year or two and I can avoid this madness.
 

superjim

Senior member
Jan 3, 2012
293
3
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After seeing the 7700 series performance, I'm worried about Pitcairn repeating it. If the 7870 does not have equal or better performance than a 6970 it will be a fail in my book at $300.
 

IlllI

Diamond Member
Feb 12, 2002
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from the recent review, it seems like ATI needs more cards to fill more price points. i'm wondering what they are going to do for the $199 tier. very doubtful that they would price a 7850 for 199, if it beats a 6950 or 6970.

or lets say they do price 7850 $199 and 7950 like $250. then
what happens at the $300-$400 range?
 

LOL_Wut_Axel

Diamond Member
Mar 26, 2011
4,310
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Going by the specs and product positioning it should be slightly faster than the 6950. Same for the 7870 and 6970.

Kinda sad that they don't have a direct replacement for the HD 6870, unless they make an HD 7830 and I highly doubt that would exist.
 

LOL_Wut_Axel

Diamond Member
Mar 26, 2011
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from the recent review, it seems like ATI needs more cards to fill more price points. i'm wondering what they are going to do for the $199 tier. very doubtful that they would price a 7850 for 199, if it beats a 6950 or 6970.

or lets say they do price 7850 $199 and 7950 like $250. then
what happens at the $300-$400 range?

HD 7950 1.5GB at the upper $300 range. And the 7870 will be at the lower $300 range.

7950 1.5GB should be $379-399 and 7870 should be $299-329.
 

Leadbox

Senior member
Oct 25, 2010
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Going by the specs and product positioning it should be slightly faster than the 6950. Same for the 7870 and 6970.

Kinda sad that they don't have a direct replacement for the HD 6870, unless they make an HD 7830 and I highly doubt that would exist.

Quiet a gap between the 10 CU 7770 and the 28CU 7950, I would expect for there to be at least 3 78** SKUs, a 7830 might just come out later built from defective cores
 

IlllI

Diamond Member
Feb 12, 2002
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yeah, i agree with leadbox. my guess is there is probably some 'secret' card that hasnt been talked about yet. something to bridge the gap between 7770 and 7850
 

Subyman

Moderator <br> VC&G Forum
Mar 18, 2005
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After seeing 79XX and 77XX series pricing I just said a prayer over my GTX 480 in hopes that it lasts for another year or two and I can avoid this madness.

I laid lays on my 470 to hold together another 6 months as well.
 

LOL_Wut_Axel

Diamond Member
Mar 26, 2011
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Quiet a gap between the 10 CU 7770 and the 28CU 7950, I would expect for there to be at least 3 78** SKUs, a 7830 might just come out later built from defective cores

They can do it, but I doubt it'd be because of hugely defective dies. The die for Pitcairn is gonna be very small, probably in the lower end of 200mm^2. At that size, even with an immature process, I don't think they'd have cards with such big defects to warrant making a 7830 so they don't completely lose money on defective dies.

At the same time, they can still just take mostly or fully functioning Pitcairn dies and laser cut them and sell them as 7830s to fill demand in a certain price point.

It could also be called the HD 7790, but only if it ends up having the same number of CUs as the HD 7770 coupled with a 256-bit bus.
 

MrTeal

Diamond Member
Dec 7, 2003
3,586
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You can probably start estimating the performance of the 7850 and 7870 at this point based on the expected configuration of Pitcairn and the performance of Cape Verde and Tahiti. Normalized to the 7770 you have 2.2x the shaders and TUs, 1.5x the ROPs, 0.95x the core clock, and 2.44x the memory bandwidth.

Compared to Tahiti, Pitcairn will have 0.69x the shaders and TUs, 0.75x the ROPs, close to the same clock speed, and 0.67x the memory bandwidth.

Cape Verde to Tahiti you see 3.2x the shaders and TU, 2x the ROPs, 0.93x the clocks, and 3.7x the memory bandwidth.

At 1200p per TPU, in BF3 the 7970 is 2.5x faster than the 7770, in B:AC it's 2.2x, in Metro it's 2.7x, in Unigine it's 2.5x. Games like Skyrim show lower gains, but they're less GPU bound.

My guess would be that the 7870 will be somewhere in the range of 70% faster than Cape Verde, which should put it around the same level as the 6970 is games like BF3, and considerably faster in games that benefit the new arch, like Civ5.
 

Concillian

Diamond Member
May 26, 2004
3,751
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You can probably start estimating the performance of the 7850 and 7870 at this point based on the expected configuration of Pitcairn and the performance of Cape Verde and Tahiti. Normalized to the 7770 you have 2.2x the shaders and TUs, 1.5x the ROPs, 0.95x the core clock, and 2.44x the memory bandwidth.

Compared to Tahiti, Pitcairn will have 0.69x the shaders and TUs, 0.75x the ROPs, close to the same clock speed, and 0.67x the memory bandwidth.

Cape Verde to Tahiti you see 3.2x the shaders and TU, 2x the ROPs, 0.93x the clocks, and 3.7x the memory bandwidth.

At 1200p per TPU, in BF3 the 7970 is 2.5x faster than the 7770, in B:AC it's 2.2x, in Metro it's 2.7x, in Unigine it's 2.5x. Games like Skyrim show lower gains, but they're less GPU bound.

My guess would be that the 7870 will be somewhere in the range of 70% faster than Cape Verde, which should put it around the same level as the 6970 is games like BF3, and considerably faster in games that benefit the new arch, like Civ5.

It's way less confusing if you use a card as reference and assume things scale with clock speed.

Example, if we call 7770 reference and it's values are 1.0
So Card -- #Shader*clock / #TMU*clock / #ROP*clock / bandwidth
7770@1000 -- 1.00 / 1.00 / 1.00 / 1.00
7850@ 900 -- 1.80 / 1.80 / 1.35 / 2.22
7870@ 950 -- 2.09 / 2.09 / 1.43 / 2.44
7950@ 900 -- 2.52 / 2.52 / 1.80 / 3.33
7970@ 925 -- 2.96 / 2.96 / 1.85 / 3.67

so 7970 is ~3x in shader & TMU & bandwidth, a little less than 2x in ROP, translating to ~2.5x. This suggests that shaders and ROP have approximately equal weight on average, but result in some differences on individual games.


So a 7850 would be around 55% faster and 7870 about 70% faster.
7850 would need to be around 1150 MHz to be double the performance of a 7770.

This assumes 7850 and 7870 will be 1280 and 1408 respectively. 7770 being 640 worries me that Pitcairn will have fewer shaders & TMUs. Seems like it must be 24 ROPs unless they do like the 68xx cards and run 32 ROPs and low core speeds, but I'd be pretty surprised at low core speed GCN.
 

LOL_Wut_Axel

Diamond Member
Mar 26, 2011
4,310
8
81
You can probably start estimating the performance of the 7850 and 7870 at this point based on the expected configuration of Pitcairn and the performance of Cape Verde and Tahiti. Normalized to the 7770 you have 2.2x the shaders and TUs, 1.5x the ROPs, 0.95x the core clock, and 2.44x the memory bandwidth.

Compared to Tahiti, Pitcairn will have 0.69x the shaders and TUs, 0.75x the ROPs, close to the same clock speed, and 0.67x the memory bandwidth.

Cape Verde to Tahiti you see 3.2x the shaders and TU, 2x the ROPs, 0.93x the clocks, and 3.7x the memory bandwidth.

At 1200p per TPU, in BF3 the 7970 is 2.5x faster than the 7770, in B:AC it's 2.2x, in Metro it's 2.7x, in Unigine it's 2.5x. Games like Skyrim show lower gains, but they're less GPU bound.

My guess would be that the 7870 will be somewhere in the range of 70% faster than Cape Verde, which should put it around the same level as the 6970 is games like BF3, and considerably faster in games that benefit the new arch, like Civ5.

Those estimates sound just about right. Also take into account the 7870 will probably be clocked at 1GHz.
 
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