Overview: Boot your mining rig using MS-DOS Boot Disk, copy the BIOS to a file, then take that file to a Windows PC where you can load the BIOS, modify it, save it back to the MS-DOS Boot Disk USB, then go back to your rig to flash the modified BIOS.

1. Preparation

  • Download Rufus so we can create a MS-DOS Boot Disk out of a USB Drive: here
  • Download VBE7.0.0.7b.exe (Video BIOS Editor) from here
  • Download atiflash 4.17 from here

2. Making the Flashing Disk

  • Unpack and run Rufus.
  • Where it says “create a bootable disk using”, make sure to select MS-DOS.
    Note: Make sure when you are creating the usb boot disk to select MSDOS and NOT FreeDOS: FreeDOS may lock up on you and the bios flash will fail.
  • Once you have the MS-DOS USB boot disk created, unpack atiflash and copy atiflash.exe on the boot disk.
  • Take the MS-DOS Bootable USB with atiflash, and stick it in the target computer with the video card you want to undervolt, and boot it up.
  • Best Practice: Only Modify one card at a time and then test it out!

  • Type the command atiflash -s [gpu number] [filename to save as]
    For example, atiflash -s 0 stock0.rom
  • That will download the bios off the first video card (GPU 0.)
  • Turn off the rig and pull the USB stick.

3. Modifying the BIOS

  • Unpack and copy the VBE7 program to a windows computer.
  • Place the USB stick into your windows computer with VBE.
  • Open the VBE software and open the file you just made with atiflash, for example, stock0.rom
  • On the powerplay tab make sure State 1 – Performance is selected.
  • Then the last 2 rows on the window are what we want to change.
  • Input your desired core clock and memory clock speed and vddc (voltage).
  • Best Practice: Save a few various settings to different files to allow you to flash, test, flash again, test, if you desire.

  • If you did 1150 as the voltage… save that to the USB drive. ie. 0-1150.rom
  • Best Practice: You will typically choose to make 4 versions of the modified BIOS. Once you copy off the bios from the gpu, and you are in VBE, Example: You make one at 1150 voltage, one at 1100, one at 1050, and one at 1000. This way you can flash each step down, test it out… if its stable, go to the 1100… etc. If for instance you crash on the 1000, then you can try making another one at 1025, until you get to the lowest stable voltage.

4. Flashing the Modified BIOS Back to the GPU

  • Take take the usb stick back to the rig with the GPUs in it.
  • Make sure the computer is shut down.
  • Best Practice: If your GPUs have Dual BIOS, this is why. You have a backup if something goes wrong. It is not required to have Dual BIOS to flash a card.

    Best Practice: Only flash one GPU at a time, that way you can boot off a good one and see the display so you can flash the stock BIOS back to the misflashed card.

  • On the video card look for a little switch, this is the Dual BIOS switch.
  • Double-check ALL power is off to your rig and these cards.
  • Flip the switch to position 2.
  • Insert your USB stick and boot up.
  • Then type atiflash -f -p [gpu number] [new bios file name]
    Example: atiflash -f -p 0 0-1150.rom
  • Now remove the flash drive and reboot into PiMP.
  • and now you have an undervolted gpu
  • If anything goes wrong, you can POWER EVERYTHING OFF, flip the bios switch back to setting 1. That way you dont risk your card being bricked.

5. Testing

    Best Practice: Use known good settings and pools and let the cards hash for about 24 hours to check for stability.

  • If you are stable at the current settings, try the next step.
  • This way you can flash each step down, test it out… if its stable, go to the 1100… etc.
  • If for instance you crash on the 1000, then you can try making another one at 1025, until you get to the lowest stable voltage.
  • Once you undervolt, dont go increasing gpu clock speed. Typically, you should only undervolt after you find the clock speed you like.

Big Thanks to Monkeytoe for showing me how to do this initially!