AMD: Southern Islands (7*** series) Speculation/ Rumour Thread

That being said, wasn't there supposed to be no reference 7950 designs but only custom ones?
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It won't oc to 1200mhz unless you add volts at least to where the 7970 is, disable power tune and the power delivery doesn't blow up on you.
Yes but with people reportedly running the HD7970 undervolted to about idle voltage (~0.85V) at stock clocks, it should still easily make it to around 1Ghz probably, because I sort of doubt the default voltage is going to be much lower than on HD7970 - a little bit lower maybe but not that much.
 
Lots of ppl hit 1.125Ghz on default volts, however have yet to actually see any card slot power consumption numbers. Full system numbers don't give an exact picture because higher cpu utilization can lead to higher use from that part as well.
 
A few interesting observations on Tahiti GPUs. First, it looks like similar to Fermi, Thaiti GPUs are binned and there are 4 types of Tahiti GPUs with different ASIC leakage level. So depending on it there are 4 possible default 3D voltages: 1.17500V, 1.11250V, 1.05000V and 1.02500V.
Currently all voltage control tools use hardcoded default voltage (1.175V) for 7970, so pressing "Reset"/"Defaults" buttons in any voltage control tool will put any GPU to 1.175V regardless of leakage level.
It looks like I have located the fuses identifying GPU leakage level, but I need more statistics on it. So if you have 7970 please run MSI Afterburner with the following command line switch:

MSIAfterburner.exe /rr174

Then post the result here, and don't forget to mention your default voltage as well.

Not exactly. Bits 4-13 of reg 174 are fuses reflecting ASIC leakage/quality, 100% quality is 3ff. So my ASIC (23e0) is 23e/3ff = 574/1023 = 56%.

AMD uses the following table to select VID depending on ASIC quality:

up to 2F90 (up to 75% quality) - 1.1750V
up to 34D0 (up to 80% quality) - 1.1125V
up to 3820 (up to 85% quality) - 1.0500V
up to 3A90 (up to 90% quality) - 1.0250V

http://forums.guru3d.com/showthread.php?p=4221583#post4221583
 
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Atlantis is correct. What you can infer from the table is that 1.175 is a safe operating voltage for the process, so if you get a high leakage running at 1.025V you have a lot of voltage headroom to tweak voltage and still be within "normal" voltage bounds for Tahiti. For sure, though, TDP will be a lot higher so you need to make sure the VRM can handle it.
 
Atlantis is correct. What you can infer from the table is that 1.175 is a safe operating voltage for the process, so if you get a high leakage running at 1.025V you have a lot of voltage headroom to tweak voltage and still be within "normal" voltage bounds for Tahiti. For sure, though, TDP will be a lot higher so you need to make sure the VRM can handle it.

Where did you get the impression that high leakage chips were running at a lower voltage? The linked posts by Unwinder clearly say that the lower voltage settings are reserved for lower leakage, higher quality chips.

Also lower voltage chips do not have higher clock headroom due to a set +125mV OVP. So you actually want a higher voltage, lower quality chip as long as power consumption and cooling are taken care of. Until somebody finds a way to bypass the over-voltage-protection of course.
 
Whats the point of running high leakage high voltage and low leakage at low voltage? You may as well run all of them at the same voltage. If you did this all you would end up doing is massively increasing the power variability within a single SKU, defeating a lot of the point of binning in the first place.

By running high leakage at lower voltage and low leakage at higher voltage you are narrowing the range of power variability of a SKU and maximising the yield of a particular SKU for a given power target.
 
IHVs do not run chips at higher voltage unnecessarily just to reduce power consumption variability. What possible benefit does that have as long as all chips come in under the rated TDP?

Anyway, did you even read the Guru3D thread or are you claiming Unwinder doesn't know what he's talking about? :)
 
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