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

[Man from Atlantis]

That being said, wasn't there supposed to be no reference 7950 designs but only custom ones?

:smile:

Spoiler

source

 

[mczak]

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.

 

[DarthShader]

I've got no doubts about reaching 1+Ghz, but I am convinced 1.2Ghz will be a no go without extra voltage.

BTW: Asus DirectCu http://www.techpowerup.com/159003/ASUS-Radeon-HD-7970-DirectCu-II-Graphics-Card-Pictured.html

10+1+1 power section and 2x8 pin supply. Wonder how high that thing goes...

 

[AlphaWolf]

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.

 

[Man from Atlantis]

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.

it's Idle 14W, Game 210W, Furmark 295W(Powertune +20%) 245W (Powertune @0)

http://ht4u.net/reviews/2011/amd_radeon_hd_7900_southern_island_test/index22.php

 

[AlphaWolf]

I meant for the 1.125Ghz OC.

 

[Man from Atlantis]

I meant for the 1.125Ghz OC.

sorry, there is also 1070MHz comsumption numbers at default voltage(223W at gaming) if it any helps.. you can extrapolate +10W at worst for gaming..

http://ht4u.net/reviews/2011/amd_radeon_hd_7900_southern_island_test/index24.php

 

[Man from Atlantis]

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

 

[Alexko]

That's a pretty huge amount of variation, isn't it?

 

[Rangers]

It's rather interesting that I've not seen even a single 1.025V chip yet. My guess that those chips are selected for upcoming 7990 (similar to 6990 using low-leakage Caymans only).

http://forums.guru3d.com/showpost.php?p=4223401&postcount=148

 

[fellix]

Looks similar to Cypress that had two selections for Vcc binning (low and high leakage chips).

 

[trinibwoy]

7950 3dmark 11 - P6139

http://oclab.ru/topic/pervyie-rezultatyi-proizvoditelnosti-videokartyi-amd-radeon-hd-7950

 

[silent_guy]

That's a pretty huge amount of variation, isn't it?

And here's probably the answer as to why they launched with 925MHz clocks.

 

[ECH]

So which offers the lowest leakage: 1.175v or 1.0250v?

Edit:
It looks like 1.0250v according to this post:
http://forums.guru3d.com/showpost.php?p=4223401&postcount=148

So, if that's right then 1.1125V is the golden gpu to have?

 

[Man from Atlantis]

So which offers the lowest leakage: 1.175v or 1.0250v?

Edit:
It looks like 1.0250v according to this post:
http://forums.guru3d.com/showpost.php?p=4223401&postcount=148

So, if that's right then 1.1125V is the golden gpu to have?

lower leakege chips use more voltages.. higher leakage chips use lower voltage so that it can clock higher..

1.0250V is high leakege chips and they can be overclocked better..

 

[trinibwoy]

No, lower voltage = lower clocks.

 

[Speccy]

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.

 

[trinibwoy]

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.

 

[Speccy]

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.

 

[trinibwoy]

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?