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[Official] AMD Radeon HD 7950/7970/7990 Owners Thread - Page 1625

post #16241 of 38701
I think ASIC quality has zero bearing on overclocking potential. First 7970 that I owned had an ~84% asic rating and couldn't overclock past 1150MHz. This was with the factory Dual-X cooler. The Lightning that I am currently in the process of refunding had an ASIC of 56% and could reach 1210-1225MHz on the core.
post #16242 of 38701
Quote:
Originally Posted by tsm106 View Post

Why don't you help yourself and do a search since you know it all?

I do NOT know it all. Otherwise I wouldn't be asking you for elabotarion. I know something about it, having read hundreds of posts on Tahiti ASIC quality and having talked about it with some hard core overclockers. So if you have something substantially more credible data to back up your opinion, I would appreciate you making it public.
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post #16243 of 38701
Quote:
Originally Posted by specopsFI View Post

I do NOT know it all. Otherwise I wouldn't be asking you for elabotarion. I know something about it, having read hundreds of posts on Tahiti ASIC quality and having talked about it with some hard core overclockers. So if you have something substantially more credible data to back up your opinion, I would appreciate you making it public.


You realize you weren't asking? And this topic is universal to processors, not just AMD gpus right? Engineering spends vast amounts of time to lower leakage power on mobile processors? Why would they bother to do this when some product manager who is already disclaimered on AMD's own site, says the exact opposite?
Quote:
Dave Baumann (@Wavey_Dave) is a Product Manager at AMD. His postings are his own opinions and may not represent AMD’s positions, strategies or opinions.


Here's what he wrote.
Quote:
Actually, it does the opposite! We scale the voltage based on leakage, so the higher leakage parts use lower voltage and the lower leakage parts use a higher voltage - what this is does narrow the entire TDP range of the product.


This is opposite of reality. High leakage require more volts (because it's leaking voltage !@#$) and low leakage require less volts. LN2 ppl prefer high leakage because it bleeds off the voltage more, meaning they can feed it more voltage. High leakage power chips need more voltage to do the same work as low leakage.


Old as dirt article on leakage power.
Quote:
As you can see, dynamic power - which does useful work - has increased relatively slowly despite the increase in CPU complexity. Leakage power, however, increases exponentially, and not linearly. It has grown quickly from a "minor nuisance" to a "circuit killing monster".

Leakage is comparable to a small hole in a waterhose of a firefighter. The more pressure (i.e. the higher the core voltage), the bigger the hole gets, and thus, the more water that leaks to the ground. The thinner the walls of the tube (i.e. smaller process technology), the quicker the holes become bigger, and the more water you lose, the harder the pumps must work to get the same amount of water to extinguish the fire. If the pumps overheat, you better throttle them down, or they will cease to work after a while.

Power Leakage happens as a part of the current, which is supposed to make our transistors switch leaks away in the substrate and finally in the ground. There are several leakage currents, but the two most important ones are the gate oxide tunnelling current and sub-threshold leakage.[3]


Real world applications of lowering leakage.

Quote:
Blaze MO typically reduces leakage by 10% to 40%. This leakage reduction comes from selectively increasing gate-lengths along non-critical paths. The gate-length biasing gives fine-grain control over the delay-leakage tradeoff of a given transistor; increasing gate length reduces leakage at the cost of transistor speed, while reducing gate length makes the transistor faster at the cost of increased leakage. In leakage reduction mode, there is no change to the overall timing performance of the device, even though leakage is significantly reduced. In timing improvement mode, the performance of the device is improved without any additional leakage.


http://chipdesignmag.com/display.php?articleId=475



Why can't you google yourself? headscratch.gif
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post #16244 of 38701
My personal observations: (I know, who gives a xxxx!) biggrin.gif

I've had over 12 7970s and 6 7950s to date and from what Ive seen, the lower ASIC cards tend to overclock higher on air but require juice to get there. Of course, some cards can dissipate the heat better than others -- thereby enhancing their stability.

Look at this 7970 Lightning (64.4% ASIC) and the required voltage it needs for stability: (yet, even w/ all that juice she stays cool) thumb.gif

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post #16245 of 38701
Quote:
Originally Posted by tsm106 View Post

You realize you weren't asking?

Yes I was. You know, when I said "Care to elaborate?" That's me asking.
Quote:
And this topic is universal to processors, not just AMD gpus right? Engineering spends vast amounts of time to lower leakage power on mobile processors? Why would they bother to do this when some product manager who is already disclaimered on AMD's own site, says the exact opposite?

Yes, it is universal. Reading ASIC quality and interpreting it is not, however. We are not in disagreement on whether or not high leakage is a bad thing, we're disagreeing on whether or not high ASIC quality as read by GPU-Z means high or low leakage.
Quote:
This is opposite of reality. High leakage require more volts (because it's leaking voltage !@#$) and low leakage require less volts. LN2 ppl prefer high leakage because it bleeds off the voltage more, meaning they can feed it more voltage. High leakage power chips need more voltage to do the same work as low leakage.

That is not my understanding at all. Electric leakage is current leaking from the chip, not voltage. When a chip is leaking current, it needs more current, not more voltage. Also, if a chip is leaking more current, it can't use as high a voltage if it is to be kept under a certain TDP. See: more leakage means less voltage for the same power consumption. That is in line with what Dave Baumann said. So is the fact that people dealing with LN2 seem to prefer Tahiti chips with a high ASIC quality percentage reading.
Quote:
Old as dirt article on leakage power.
Real world applications of lowering leakage.
http://chipdesignmag.com/display.php?articleId=475
Why can't you google yourself? headscratch.gif

Cause Google don't seem to know what you know.
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post #16246 of 38701
Current and voltage are inter-related. I see this is going no where.
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post #16247 of 38701
Quote:
Originally Posted by specopsFI View Post

I would argue it is the opposite. Higher ASIC means lower VID, but at least for AMD it means a higher leakage chip. AMD wants to balance the power consumption between the chips, which means they use lower VIDs for chips with higher leakage. Seeing how my 84.3% ASIC card shoots up in power consumption and temperature when put on similar voltage as my 75.5% card, I can only come to this conclusion. I have also read a lot of hard core OCers saying they love high ASIC quality 7970s for LN2. For air, a card with a lower ASIC quality would be better.
From the horse's mouth: http://forum.beyond3d.com/showpost.php?p=1344008&postcount=29

70%, 72% here, both do over 1300 under water. In your comment which is in BOLD I would say the opposite. More of a trend than an absolute though, chip lottery in play too.

Quote:
Originally Posted by Majin SSJ Eric View Post

I can tell you that high ASIC ain't great for water. Both my 7970's are over 84% but they won't budge beyond 1230MHz no matter the voltage...

I would agree with this.
post #16248 of 38701
Quote:
Originally Posted by Mazel View Post

I hear the lightning is problematic, and yes I believe that voltage is right. That's what I typically get with the second bios. Otherwise that seems really hot, just use the first bios which has a voltage of 1.2.
Quote:
Originally Posted by tsm106 View Post

Iirc, that's the boost voltage, but it's not a real voltage since AB cannot read real voltage and instead display "intended" voltage.
Quote:
Originally Posted by m3t4lh34d View Post

Problematic? It's one of the best, if not the best 7970 available right now. Plus there are water blocks available for it. I've got 4 and they easily match or beat my 680s depending on the game and OC.

Yeah the Sapphire card is on its way back to get a refund. One of the VRMs got up to 120C and a few minutes later the card started flickering the screen.

I got a Lightning on the way! So excited! biggrin.gif
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post #16249 of 38701
Quote:
Originally Posted by tsm106 View Post

Current and voltage are inter-related. I see this is going no where.

It could be going somewhere. I haven't made up my mind, but I've received a lot of data to support the "higher ASIC % = higher leakage". That includes my own testing, where the higher ASIC % card has the same power consumption with a voltage of 1.05V than my other card with a lower ASIC % with a voltage of 1.112V. This would indicate that a higher ASIC % = lower VID voltage = higher current leakage = about the same TDP.
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post #16250 of 38701
12.9 Beta on AMD site:http://support.amd.com/us/gpudownload/windows/Pages/radeonaiw_vista64.aspx
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