XFX HD 7950 optimization and overheating

[franciz]

Hello everyone, my name is Francisco and I am from Argentina.
I am new to mining and wanted to ask a few questions.

1) I bought two second hand XFX HD 7950 (FX-795a-tn) and I am trying to build my rig to mine altcoins. I am testing with one card only to see if everything works well.
This is my cgminer.conf

Code:

{
"pools" : [
   {
      "url" : "xxxxxxxxxxxxxxxxxxxxx",
      "user" : "xxxxxxxxxxxxxxxxxxxxx",
      "pass" : "1"
   }
],

"kernel"         : "scrypt",
"scrypt"            : true,
"no-submit-stale" : true,
"temp-overheat"         : "80",
"temp-cutoff"  : "90",
"temp-target"  : "70",

"intensity"      : "20",
"vectors"       : "1",
"worksize"     : "256",
"gpu-fan"        : "auto",
"gpu-powertune"        : "20",
"thread-concurrency" : "24000",
"gpu-threads"  : "1",
"expiry"           : "120",
"no-pool-disable"        : true,
"log"                : "5",
"shares"          : "0",
"queue"           : "1",
"scan-time"      : "60",
"temp-hysteresis" : "3"
}

With this configuration sometimes I open cgminer and sometimes it mine at 600khs avg but most times it mine at 530khs avg. I do not know why because I don't change anything.
Is this configuration ok??

2) Temperature when mining gets up to 80-82º C and I wanted to undervolt to get it down a bit. This card cannot be undervolted via trixx, afterfurner or gpu tweaker. The only possible way is via bios modification, but this card do not have the bios recovery switch and also has checksum. That is why I am afraid of doing it, I don't want to brick the card...
Should I take the risk and try to modify the bios?? Did someone here did it succesfully on a similar card??

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[Benson Samuel]

Open out your cabinet and point a table fan at it. It will drop the temp by several degrees.

[franciz]

I have put two common PC fans (8 cm) pointing directly at the card, but they don't seem to be doing any effect. The temp went down only by 2 degrees.
I read lost of post of people complaining of this XFX cards, I should have investigated a bit earlier. ? 

Do you think the bios change is doable?
Is it easy to recover using a second card if everything goes wrong?

Thanks!!

[LiteMine]

You're right, you could brick your card trying to change it.

The heat might be the card, no experience with those. Take your entire mobo out of the case, get a crate (office supply store) and put a fan directly on it. Buy card risers and your temps should drop. Lots of crate builds in the forum, just search.

https://bitcointalk.org/index.php?topic=163306.0

[franciz]

I took the risk and flash the card with a modified 1084v bios, the original was 1250v.
The temperature only came down by 5º. It was at 84º and now it is at 79º.
Atiwinflash backed up a 256 kb rom, this one do not work. Use the  gpu-z backup that is 128kb.
There is no need to for correct checksum. I am just clarifying since this were all the doubts I had.
The undervolt worked fine, but apparently this card is really hot either way.

EDIT: Still testing, at 1000mv, temperature is at 78º but fan velocity went down from 4000 to 3600 rpm. I read that at low voltage the 7950 cards went down to 65 or 70º. But this XFX must be really bad quality because it is still really hot.

EDIT2: I flashed a 975mv bios and when I opened cgminer, it never started mining.
Then I bricked the card, fixed it using an Nvidia as primary, and went back to 1000mv.
I had never flashed an ati card before. It seems ati cards are really good when it comes to flashing bios, you can fix a bricked card really easy.

TIP: If you use atiwinflash and it says bios upload failed, NEVER reboot the pc. Just wait a minutes and try again until the bios uploads succesfully.