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Author Topic: Undervolting help: XFX DD 7950 supports overvolting but not undervolting?  (Read 7223 times)
netvope
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April 01, 2013, 07:06:09 PM
 #1

I've a XFX Double D Radeon HD 7950 (FX-795A-TDFC) with 2 DVI ports. Interestingly, I can only increase the voltage of the card but not decrease it. Here is the voltage table set by the manufacturer:

Code:
Core clock     VDDC
below 701 MHz  950 mV
701-850 MHz    1069 mV
above 851 MHz  1169 mV

The default core clock of this card is 900 MHz. At that speed, no matter what I do, the voltage won't go below 1.169 V. TriXX and AfterBurner allows me to set a lower voltage (say 0.9 V), but the card will simply ignore it. GPU-Z will show 1.169 V, and the power consumption measured at the wall won't decrease.

On the other hand, overvolting does work. I can set it to 1.2+ V and reach 1100+ MHz. GPU-Z will show the voltage I set, and the power consumption measured at the wall will increase rapidly as I change the voltage.

List of things I've tried:
Use Windows 7/8 x64
Use Catalyst 13.1 and 12.3
Sapphire TriXX: force constant voltage
MSI AfterBurner: force constant voltage and extend overclocking limit
ASUS GPU Tweak: disable 2D clocks and extend overclocking limit

Any idea how I can undervolt this card?
Could it be that it's hardware locked to allow only overvolting but not undervolting?

Any help is appreciated Smiley
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tacotime
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April 01, 2013, 07:24:10 PM
 #2

I will rip my older XFX DD 7950 bios later and put it up, that may fix this

Code:
XMR: 44GBHzv6ZyQdJkjqZje6KLZ3xSyN1hBSFAnLP6EAqJtCRVzMzZmeXTC2AHKDS9aEDTRKmo6a6o9r9j86pYfhCWDkKjbtcns
netvope
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April 01, 2013, 07:30:19 PM
 #3

I will rip my older XFX DD 7950 bios later and put it up, that may fix this

Thank you. I'll send you 10 LTC for the help if it works! (Assuming you don't hate LTC Wink)

I contacted XFX technical support about that. They say that the 2 DVI version is voltage locked (which is not true as overvolting works) but the 1 DVI version is not. Which one do you have?
tacotime
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April 01, 2013, 07:34:46 PM
 #4

I have the 1 dvi

Code:
XMR: 44GBHzv6ZyQdJkjqZje6KLZ3xSyN1hBSFAnLP6EAqJtCRVzMzZmeXTC2AHKDS9aEDTRKmo6a6o9r9j86pYfhCWDkKjbtcns
netvope
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April 02, 2013, 04:42:26 AM
 #5

Tried 8 BIOSs with the same device ID from the TechPowerUp Video BIOS Collection. Unfortunately, none of them unlocked undervolting for me. Some of them actually increases the power consumption significantly (both idle and load).

Using the stock BIOS, the power consumption of the system (with GPU load) is ~264W

HIS.HD7970.3072.120816.rom
Works, but the voltage table is exactly the same as stock

ATI.HD7950.3072.120706.rom/HIS.HD7950.3072.120706.rom (idential ROMs)
Does NOT work

ATI.HD7950.3072.120116.rom
GPU-Z reports a lower voltage at load, but power consumption increases to ~452 W

MSI.HD7950.3072.120202.rom
GPU-Z reports a lower voltage at load, but power consumption increases to ~450 W

VTX3D.HD7950.3072.120822.rom
Does NOT work

Sapphire.HD7950.3072.120706.rom
Does NOT work

Sapphire.HD7950.3072.120731_1.rom
Does NOT work

Sapphire.HD7950.3072.120907.rom
GPU-Z reports a lower voltage at load, but power consumption increases to ~320 W
tacotime
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April 02, 2013, 05:08:57 AM
 #6

here you go

http://multiupload.nl/0KT86M1T1L

Code:
XMR: 44GBHzv6ZyQdJkjqZje6KLZ3xSyN1hBSFAnLP6EAqJtCRVzMzZmeXTC2AHKDS9aEDTRKmo6a6o9r9j86pYfhCWDkKjbtcns
netvope
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April 02, 2013, 05:38:57 AM
 #7


Thanks for trying to help. Your BIOS works with my card, but unfortunately I still cannot undervolt. Like some of the other BIOS I've tried, it significantly increases the power consumption (to ~450W). So I'll revert the the original BIOS for now

Now I think it's safe to assume that they've changed the components on the board
ryantc
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April 03, 2013, 05:06:24 PM
 #8

.....was thinking to get this one, it seems cheaper but without unlocked voltage......Er.....no
Zisef
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January 14, 2014, 06:33:35 PM
 #9

Has any one had any luck unlocking these cards? They run WAY TO HOT, and consume to much power!
Wipeout2097
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January 14, 2014, 06:49:56 PM
 #10

http://www.techpowerup.com/forums/threads/vbe7-vbios-editor-for-radeon-hd-7000-series-cards.189089/

If that doesn't work, nothing does.


 
 
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G K G
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January 15, 2014, 03:15:26 AM
 #11


has anyone tried this. I've ordered the 4 of those same cards. need to know beforehand what to do

And what is the hashrate with the stock voltage?

badbrains
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January 15, 2014, 05:01:52 AM
 #12

I have successfully lowered voltage by modifying the bios. I have a bunch of XFX 7950 Core Edition DD that are voltage locked and ran very hot. After modifying the bios I can run a stable 630kh/s at about 77c with pretty mild overclock and a fan blowing on the rigs. Without external fan and a milder oc each card is stable at around 600kh/s. Before the reflash I was constantly above 85 degrees pushing 90. Stock kh/s is around 450 if I remember correctly.

Software you'll need:
VBE7
atiflash
GPU-Z
HPUSBDisk

-USB key to boot from.
-Google


1.081v, Clocks at 1075/1250, 79c, 639kh/s

microman2006
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January 31, 2014, 09:41:23 PM
 #13

could you post your modified BIOS? i have been trying and no success.
uranian
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February 11, 2014, 03:42:53 PM
 #14

could you post your modified BIOS? i have been trying and no success.

you need to edit the BIOS via VBE7; once you change the boot voltage there, you can then edit the voltage via CGminer. that's the only way i've found to undervolt these cards, after a lot of trying.
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