My Saphire 380x betrayed 21,3mh before editing. BIOS for extraction using ATIFlash 2.74 https://www.techpowerup.com/downloads/2728/atiflash-2-74 Run as administrator, and select Save.
Use any hex editor, for example http://www.hhdsoftware.com/Download/free-hex-editor-neo.exe
A need also TongaBiosReader https://github.com/Hedzin/TongaBiosReader/archive/master.zip
Timings will be taken from the frequency of 1500 and copied in 1625 and 1750. Opening a saved BIOS Editor and look for the combination of "7177".
We look at 3 bytes to the value found: f0 49 02, we swap and get 0249f0. Сonvert this number from hexadecimal to decimal. Get the number of 150,000, this is 1500 MHz. Select the piece of code starting from 7177 up to the next area (highlighted in red). Before the marked red reserve 4 bytes (this is the next frequency).
Paste. Red highlighted the next frequency, doing the same thing, bytes c4 7a 02 - 027ac4 - 162500 - 1625MHz.
The same is done for the frequency of 1750MHz. But my memory does not work at that frequency. The maximum stable frequency 1650MHz (Elpida). In mining to about 23mh. You can try to copy this piece of code from another card. Where memory is faster and less timings (MSI, Asus, EVGA). Maybe that speed will increase a little.
Note: If the corrupted card with the firmware switch to 2 bios, boot, switch back and sew again. After editing changes checksum. And flasher will not sew. To correct checksum need to open the edited file in TongaBiosReader and overwrite the file.